PHJ_21

Public Health Bayer Environmental Science Journal No. 21 February 2010

CHAGAS DISEASE AND AFRICAN SLEEPING SICKNESS Both diseases are caused by the same pathogen: protozoan blood parasites of the genus Trypanosoma. In Latin America Chagas disease is transmitted by bugs of the subfamily Triatominae (above left). In Africa the vector for sleeping sickness is the tsetse fly of the family Glossinidae (below; also back cover). Both diseases can be eliminated as serious health problems through coordinated strategies based around vector control.

PUBLIC HEALTH JOURNAL 21/2010

K E Y F A C T S

TRYPANOSOMIASIS IN LATIN AMERICA AND SUB-SAHARAN AFRICA

“Kissing” bugs and Chagas disease

Trypanosomes causing Chagas disease in Latin America are transmitted by blood-feed-ing Triatominae bugs. The parasites multiply in the bug’s gut and can be excreted on to the skin by the bug during its next blood meal. Scratching the highly irritable insect bite results in rubbing parasites into the wound to cause infection.

• More than 13 million people are infected by this parasite. 50,000 new infections p. a.

• 30 million people in 21 countries in Latin America are at risk of infection.

• 15,000 deaths are expected per year from Chagas disease.

Tsetse flies and sleeping sickness

Only found in sub-Saharan Africa, tsetse flies transmit trypanosomes causing the disease sleeping sickness. The life cycle of these parasites is highly complex (see box right) relying on the particular devel-opment of these blood-feeding flies.

• Estimated number of infected people is currently 500,000.

• Treatment is very difficult and the disease is lethal if untreated.

• Sleeping sickness threatens more than 60 million people as well as their live-stock in 35 countries in sub-Saharan Africa.

Development of Trypanosoma brucei in the tsetse fly *

Tsetse infested areas

(tsetse belt)

Ingestion of the trypanosomes with a blood meal

Transformation in the crop

Transport to the mid-gut

Replication

Day 10 penetrate peritrophic membrane

1

2

3

4

5

1 2

3

4 56a

6b

6c

6d

7a 7b

8b

8c

8d

8a

Trypanosomiasis

American (Chagas disease) and African (sleeping sickness) trypano-somiasis are caused by protozoan parasites of the Genus Trypanosoma but by different species: • Chagas disease is caused by

Trypanosoma cruzi• Sleeping sickness is caused by

Trypanosoma brucei

The sleeping sickness parasite must go through a long and complicated process in the tsetse fly. Whereas trypanosomes get as much energy as they need from glucose in peoples’ blood, when the tsetse fly sucks them into its gut, conditions change dramatically. Here, the fly digests all the blood sugar, so parasites must remain in the insect’s crop to have a chance to build up their own energy produc-tion system (mitochondria). But this takes time, so only parasites taken up by the tsetse fly’s first blood meal survive. Upon emerging from the pupa, the peritrophic membrane protecting the fly’s gut wall is still short and closed at the end. It takes 4 hours to develop – until then food stays in the crop and the trypanosomes have enough time to transform. Then they can progress through the peritrophic mem-brane, gut wall and on to the saliva glands and proboscis, ready to return to the blood of the fly’s next victim.

Triatominae infested areas

See articles on page 6 and 16 See articles on page 23, 32, 38 and 58* This diagram was kindly provided by Günther Nogge and is published here for the first time.

Penetrate through the mid-gut wall

Migrate directly to salivary glands

Convert to epimastigote form – replicate – develop into metacyclic form

Transmission with saliva

7a

7b

6c

6d


Develop into metacyclic form

Migrate to proboscis

Transmission by proboscis

8b

8c

8d

8a6a

6b

6c

6d

Leave the ecto-peritrophic space near the valvula cardiaca

Migrate to the salivary glands via the pre-gut and proboscis



Three di f ferent ways

Available as poster on the enclosed Public Health CD-ROM

TRYPANOSOMIASIS IN LATIN AMERICA AND SUB-SAHARAN AFRICA

“Kissing” bugs and Chagas disease

Trypanosomes causing Chagas disease in Latin America are transmitted by blood-feed-ing Triatominae bugs. The parasites multiply in the bug’s gut and can be excreted on to the skin by the bug during its next blood meal. Scratching the highly irritable insect bite results in rubbing parasites into the wound to cause infection.

• More than 13 million people are infected by this parasite. 50,000 new infections p. a.

• 30 million people in 21 countries in Latin America are at risk of infection.

• 15,000 deaths are expected per year from Chagas disease.

Tsetse flies and sleeping sickness

Only found in sub-Saharan Africa, tsetse flies transmit trypanosomes causing the disease sleeping sickness. The life cycle of these parasites is highly complex (see box right) relying on the particular devel-opment of these blood-feeding flies.

• Estimated number of infected people is currently 500,000.

• Treatment is very difficult and the disease is lethal if untreated.

• Sleeping sickness threatens more than 60 million people as well as their live-stock in 35 countries in sub-Saharan Africa.

Development of Trypanosoma brucei in the tsetse fly *

Tsetse infested areas

(tsetse belt)

Ingestion of the trypanosomes with a blood meal

Transformation in the crop

Transport to the mid-gut

Replication

Day 10 penetrate peritrophic membrane

1

2

3

4

5

1 2

3

4 56a

6b

6c

6d

7a 7b

8b

8c

8d

8a

Trypanosomiasis

American (Chagas disease) and African (sleeping sickness) trypano-somiasis are caused by protozoan parasites of the Genus Trypanosoma but by different species: • Chagas disease is caused by

Trypanosoma cruzi• Sleeping sickness is caused by

Trypanosoma brucei

The sleeping sickness parasite must go through a long and complicated process in the tsetse fly. Whereas trypanosomes get as much energy as they need from glucose in peoples’ blood, when the tsetse fly sucks them into its gut, conditions change dramatically. Here, the fly digests all the blood sugar, so parasites must remain in the insect’s crop to have a chance to build up their own energy produc-tion system (mitochondria). But this takes time, so only parasites taken up by the tsetse fly’s first blood meal survive. Upon emerging from the pupa, the peritrophic membrane protecting the fly’s gut wall is still short and closed at the end. It takes 4 hours to develop – until then food stays in the crop and the trypanosomes have enough time to transform. Then they can progress through the peritrophic mem-brane, gut wall and on to the saliva glands and proboscis, ready to return to the blood of the fly’s next victim.

Triatominae infested areas

See articles on page 6 and 16 See articles on page 23, 32, 38 and 58* This diagram was kindly provided by Günther Nogge and is published here for the first time.


Migrate directly to salivary glands



7a

7b

6c

6d


Develop into metacyclic form

Migrate to proboscis

Transmission by proboscis

8b

8c

8d

8a6a

6b

6c

6d

Leave the ecto-peritrophic space near the valvula cardiaca

Migrate to the salivary glands via the pre-gut and proboscis



Three di f ferent ways

PUBLIC HEALTH JOURNAL 21/20102 |

C O N T E N T

5

Editorial

6

Elimination of Chagas disease

An end in sight?by C.J. Schofield

C O V E R S T O R Y

23

T R Y P A N O S O M I A S I S

4

16

Chagas disease control in Brazil

Past successes and future perspectivesby João Carlos Pinto Dias

PATTEC

Campaign against tsetse fliesby John P. Kabayo

Background

Chagas disease and African sleeping sickness: Multiple involvement of Bayerby Gerhard Hesse

32

Using insecticides to control tsetse flies

A very effective optionby G.A. Vale, I. Maudlin and S.J. Torr


C O N T E N T

M A L A R I A

48

53

59

Cover photos: Fotosearch (large picture); Michelle Cornu

5557

CD-ROM

38

The role of the sterile insect technique (SIT) in tsetse control

Using a pest to attack itselfby Udo Feldmann and Andrew Parker

LNs and IRS

Cost and effects of large-scale vector controlby Christian Lengeler and

Joshua Yukich

NGO DR CongoMalteser International

NGO UgandaOur Children and our Future e.V.

Notes

History100th anniversary of describing the tsetse fly as vector of sleeping sickness 58

43

Malaria prevention with insecticide-treated nets

How long does a long-lasting insecticidal net last in the field?by Albert Kilian

4 | PUBLIC HEALTH JOURNAL 21/2010

As the new President this is my first Public Health Journal and I am happy and proud to continue the outstanding tradition of this publication. This edition mainly focuses on protozoon parasites of the trypanosome family, previously introduced in our Public Health Journal on Neglected Tropical Diseases (No. 19). Infection by these parasites cause afflictions known as sleeping sickness in Africa and Chagas disease in Latin America – both extremely difficult to treat.

Besides vector control, Bayer has a long tradition in both health care and animal health related to these diseases. The burden is not only long-term suffering or death, but also socio-economic problems associated with the extreme poverty these diseases create. Risk of infection of people and livestock means African farmers avoid vast areas infested by the disease vector, the tsetse fly. In Latin America, more than 13 million people suffer from Chagas disease. And it is estimated that about 0.5 million people in Africa are infected with the parasite that causes sleeping sickness.

Efforts to control these diseases also have a long and varied history. Only recently authorities have started to prioritize the sustainability of vector control with a view to elimination. Here, once again we are pleased that international experts in their fields have contributed highly informative articles on different aspects of these diseases, focusing on transmission, the vectors and strategies to control them.

Two articles set the scene for realizing the ultimate goal of eliminating such vector-borne diseases. Efforts to eliminate the vectors on a very large scale play a major role, backed up with surveillance for re-infestation and disease treatment. These are also themes that recur throughout the journal with reference to both triatomine bugs in Latin America and the tsetse fly in Africa.

Besides our main theme we also focus on two interesting aspects in the fight against malaria. One report addresses the important question of assessing the effective life-span of long-lasting insecticidal bednets in the field and how long they continue to protect the user. The other compares the two major vector control strategies of insec-ticidal nets and indoor residual spraying, weighing up their cost-effectiveness and impact on malaria transmission.

Finally, our history article commemorates the discovery 100 years ago that the tsetse fly transmits the trypanosome parasite in Africa. Which returns us to our main theme of these parasites and their vectors.

We wish you pleasant reading.

GUNNAR RIEMANN Member of the Bayer

CropScience Executive Committee and President of the Environmental Science

Division Worldwide

E D I T O R I A L

Gunnar Riemann

PUBLIC HEALTH JOURNAL 21/2010 | 5

Bayer Environmental Science is actively engaged in preventing the transmission of trypanosomiasis by controlling the vectors. This involves various intervention methods and techniques in combina-tion with education, training, environmental sanita-tion, safe housing, etc. All these measures together form the basis for Integrated Vector Management. This in turn is the foundation for Integrated Disease Management, which uses a number of different strategies to achieve long-term solutions to disease problems.

Indoor residual spraying is the classical tool for controlling the Chagas disease vector in homes. However, some species have peri-domestic habitats as they also feed on livestock. This area can be treated as well as the livestock itself. Here, Bayer Animal Health offers a portfolio of products to keep companion animals and livestock safe and healthy.

In addition to vector control, Bayer Health Care produces very effective trypanocidal drugs. Suramin (Germanin), the first drug to treat African sleeping sickness, was synthesized in 1916 by Bayer chemists Oskar Dressel and Richard Kothe (see page 58).

Nifurtimox was developed in the 1960s to combat the Chagas disease. After a short interruption pro-duction of this drug was resumed in 2000. This was not only to enable treatment of Chagas

patients but also allowed clinical studies for African sleeping sickness. Bayer Schering Pharma signed an agreement with WHO in September 2009 to supply Nifurtimox for the Nifurtimox-Eflornithine Combination Therapy (NECT). This is the first new treatment option for African sleep-ing sickness in 25 years.

Vector control in African sleeping sickness, or nagana when affecting animals, means controlling the tsetse flies. Various technologies are available from aerial and ground spraying, attracting the flies to insecticide-treated traps and targets to cattle treatment with suitable ectoparasiticides. Bayer Animal Health and Bayer Environmental Science have an adequate portfolio for these strategies and invest in product development for new formula-tions.

Controlling or ideally eliminating trypanosomiasis in Africa is not only a requirement for human health, but also for livestock and agricultural pro-duction. Huge areas of land are unavailable for cattle breeding, or agriculture since farming ani-mals cannot be used. This is why the tsetse belt where the vector species prevail is also called Africa’s green desert.

Multiple involvement of BayerBayer is engaged at many levels in efforts to combat the trypanosome diseases Chagas and African sleeping sickness. Bayer Environmental Science is responsible for vector control, which plays a major role. But the commitment of Bayer is much more comprehensive – with a long history of developing drugs to treat these protozoan infections.

Chagas disease and African sleeping sickness

B A C K G R O U N D

The author: Gerhard Hesse, Head of Global Vector Control and editor of Public Health Journal, Bayer Environmental Science


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Typical housing in Latin America at risk of infestation with triatomine bugs.

AN END IN SIGHT?

Elimination of Chagas disease

Over 80% of Chagas infections in Latin America are passed on by domestic insect vectors. Chris Schofield outlines how eliminating these on a very large scale would stop disease transmission, as well as the risk of insect vectors spreading elsewhere in the world. Early disease detection and treatment combined with continued surveillance for insect re-infestation are essential to meet the challenge of eliminating Chagas disease as a public health problem.

C O V E R S T O R Y


C O V E R S T O R Y


Their black fecal streaks mark the walls and furni-ture, sometimes making a thick congealed patina over the walls of heavily infested houses. At times, people can no longer sleep in their houses, continually molested by the bugs. They become tired, stressed, investing scarce resources to try to get rid of the bugs. And sometimes the families divide, unable to continue under such conditions.

In 1984, it was estimated that over 100 million people in Latin America were suffering this way, and that 24 million were already infected with Chagas disease.2

Treatment of the disease is difficult. Two drugs – nifurtimox made by Bayer in El Salvador, and benznidazole now made by LAFEPE (under license from Roche) in Brazil – can be used during the acute phase of infection. These are gradually being introduced for treatment of early chronic infections (children up to 14-15 years old). Neither is completely effective, and both pose a risk of severe side-effects – especially in adult patients. But by contrast, elimination of the domestic insect vectors is a relatively simple task – at least on a small-scale, and using adequate products applied by well-trained professionals (see box on page 11: Spraying procedures). The problem is how to do this on a very large-scale, because the endemic area for Chagas disease covers well over 12 mil-lion km2 of Latin America (see map on the right).

Chagas disease vector control

Since the pioneering work of Carlos Chagas and colleagues in Brazil, and Salvador Mazza and col-leagues in Argentina, a very wide range of vector control methods have been tested with a view to eliminating domestic infestations of Triatominae – including biological control and insect patho-gens, as well as a range of physical and chemical

hagas disease (American trypanosomia-sis) is a terrible affliction, caused by infection with protozoon parasites

(Trypanosoma cruzi) mainly transmitted to humans in the fecal deposits of large blood-suck-ing insects of the subfamily Triatominae. It can be fatal in its early acute stage, but more usually progresses to a lifelong debilitating condition dur-ing which the parasites cause progressive tissue destruction as they multiply in infected cells. When the tissue affected is the heart, the patient is lethargic, with cold extremities, and quite unable to work. It is this long-term debility that, in epide-miological terms, is mainly responsible for the high socio-economic cost of the disease.

Continually molested by bugs

Even without the infection however, living in a house infested with Triatominae is very unpleas-ant. The bugs typically live in cracks and crevices of rural homes, emerging at night to feed on the sleeping occupants. There may be a few hundred, or several thousand individual bugs – the “record” is a house in Colombia, dismantled to reveal over 11,300 bugs.1 The bugs are large, adults usually about 2.5 cm long, and they suck a lot of blood, contributing to chronic iron-deficiency anemia.

C

The author: C.J. SCHOFIELD

ECLAT Coordinator London School of

Hygiene and Tropical Medicine, UK

Serious lesions

Around 30% of those suffering from Chagas disease will develop serious lesions, mainly of the heart, but in some cases also involving other vital organs such as the intestinal tract. Destruction of heart tissue can lead to severe arhyth-mias, repeated heart attacks, and sudden death due to cardiac arrest or ventricular fibrillation. More common, however, is simple pump failure due to extensive pancarditis with muscle fiber destruction.

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methods. The resulting experience accumulated from experiments and field trials in most countries of Latin America has led to a basic vector control approach with three main components:

• Indoor residual spraying (IRS) by trained professionals (see box on page 11).• Householder and community participation in monitoring and surveillance.• Rural house improvement.

By itself, rural house improvement seems insuffi-cient to eliminate an established domestic bug population3 and it tends to be a relatively slow process that rarely reaches all the poorest house-holders. By contrast, well-managed IRS programs can reach all domiciles, and can usually treat 2-10 houses per man per day – depending on terrain, size and distribution of houses, and the extent of peridomestic structures that are included in the treatment. However, community agreement and householder participation are essential, both to assist in preparing the premises for spraying, and also to participate in post-control monitoring and

surveillance. This is to ensure that the domestic bug population has indeed been eliminated and to provide early warning if any subsequent infesta-tions are found.

In general, a well applied IRS campaign is suffi-cient to eliminate existing domestic bug popula-tions, although repeat treatments are sometimes given after 3-6 months.4 Since the 1980s, WP or SC formulations* of pyrethroids have been the products of choice (see table on page 12). Other classes of insecticide are not generally used except where donated (or against some recently reported foci of pyrethroid resistant Triatoma infestans in southern Bolivia and northwestern Argentina). Throughout Latin America, IRS campaigns fol-lowed by long-term surveillance have been the primary component of Chagas disease control programs. This is combined with improved blood-bank screening to reduce the likelihood of transfu-sional transmission from infected blood donors, and improved patient care, counselling, and treat-ment for those already infected.

C O V E R S T O R Y

THE MAP SHOWS the various initiatives where countries in different regions have joined forces to bring Chagas disease under control. Each region has to deal with different vectors and problems requiring specific strategies.

Chagas disease control initiatives

Andean Pact (IPA) Venezuela, Colombia, Ecuador, Peru

Amazonia (AMCHA)Venezuela, Colombia, Ecuador, Peru, Brasil, Bolivia, Guyana, Suriname, French Guiana

Southern Cone (INCOSUR)Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay, (southern Peru)

Central America (IPCA)Guatemala, Belize, El Salvador,Honduras, Nicaragua, Costa Rica,Panama

Mexico

* WP = wettable powder; SC = suspension concentrate

C O V E R S T O R Y


Multinational control initiatives

Following a great many trials, and national control campaigns in Venezuela, Argentina, and Brazil, the enlightened response to the geographical scale of Chagas disease control came as a series of mul-tinational initiatives. These began with the Southern Cone countries (INCOSUR) in 1991, followed by initiatives of the Andean Pact (IPA) and Central American countries (IPCA) launched in 1997, and the Amazon Initiative (AMCHA) launched in 2002.

The Southern Cone Initiative (INCOSUR) involves six countries (Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay) which, with southern Peru, was designed to cover the entire distribution of the main vector, Triatoma infestans. At the time, it was believed that T. infestans was almost entirely domestic throughout its range. Small sil-vatic foci (see box above: Vector populations) were only thought to occur in the Cochabamba-Sucre region of central Bolivia. The aim of the INCOSUR program was to halt Chagas disease transmission by eliminating all domestic popula-tions of T. infestans, with concurrent elimination of any other domestic vector populations in the same area. This was combined with improved screening of blood donors to reduce the risk of transfusional transmission.

The idea was that simultaneous vector control programs throughout the area would prevent re-infestation of treated premises by T. infestans being accidentally transported from non-treated regions. In addition, the multinational nature of the program – coordinated by the Pan American Health Organization (PAHO) – should give politi-cal continuity to the interventions, making it less likely that a country would suddenly divert resources away from the Chagas disease control program.

The Andean Pact (IPA) and Central American Countries Initiatives (IPCA) had similar aims and rationale. Here, the focus was on eliminating domestic populations of their main vector, Rhodnius prolixus, together with control of other vectors in the region – particularly T. dimidiata. There was strong evidence that R. prolixus had been accidentally imported from Venezuela into Central America at the turn of the last century5, so that in Central America it appeared that R. prolixus could be completely eliminated. Similarly, there was evidence that T. dimidiata had been acciden-tally transported from Central America to Ecuador and northern Peru during pre-colombian times, so that it could potentially be eliminated from there, even if not from Central America where it retains extensive silvatic populations.

Vector populations

Domestic: live and breed in cracks in the walls of rural hous-es and animal shelters, feeding on the blood of the inhabitants

Peridomestic: live in areas near housing feeding on wild and domesticated animals Silvatic: live in woods and sur-rounding areas, under tree bark, in birdnests, rockpiles, palmtree crowns, or burrows of small mammals, sometimes entering houses and contaminating food or drink Photo: Brand X Pictures

C O V E R S T O R Y


Î Spray thoroughly all internal surfaces (including furniture and the internal roof): Use a good quality compression sprayer (eg. Hudson X-pert or equivalent) with an appro-priate product at the specified dose (see table on page 12), closely following professional spray procedures to ensure complete coverage (see: WHO Manual for Indoor Residual Spraying, below); complete your spray record-ing cards.Note: all structures physically in contact with the house should be considered as domestic for purposes of spraying and recording results.

Ï Discuss with the householders: Ask them to collect any dead bugs they find (and provide a plastic bag in which they can be stored for collection); explain safety issues, such as avoiding excessive contact with the sprayed surfaces; after 15 minutes, help the householders to replace their furniture and utensils. Pin your visit/activity card to the inside of the main door, and explain that a member of your team will return within one week to check all is well – and also to enlist the householders help in longer-term vigilance against any future infestations. Collect all used packaging from the spraying (to be returned to your supervisor).

How to eliminate a domestic population of TriatominaeS P R A Y I N G P R O C E D U R E S

Ê Identify the house – preferably using a GPS to identify the house by its geographical coordinates.

Ë Identify yourself, and explain your objec-tives to the householders, seeking their permis-sion to enter.

Ì Check for evidence of domestic infestation: Discuss with the householders, showing them life-size pictures of the bugs; check for streaks of bug feces on the walls, exuviae (the skins cast when a triatomine bug moults to its next stage), bug eggshells and bugs themselves (using a torch and long blunt forceps to investigate for bugs in cracks and crevices). You might also use a dislodgant spray (eg. 0.2% aqueous tetramethrin) to irri-tate bugs to get them to emerge from their crevices.

Í Prepare the house for spraying (if there is evidence of infestation): Explain to the householders, and seek their cooperation; remove to the outside all foodstuffs, kitchen utensils, animals and people; move furniture away from the walls to allow access behind; hang all clothes and bed linen outside in the sun.

Further details on these procedures:

WHO Manual for Indoor Residual Spraying: http://whqlibdoc.who.int/hq/2007/WHO_CDS_NTD_WHOPES_GCDPP_2007.3_eng.pdf

WHO Field testing and evaluation of insecticides for indoor residual spraying against domestic vectors of Chagas disease: http://whqlibdoc.who.int/hq/2001/WHO_CDS_WHOPES_GCDPP_2001.1.pdf

The following points describe the recommended procedures for spraying, using approved products applied by well-trained professionals. The recommendations are based on experience collected from control trials and programs throughout Latin America.

C O V E R S T O R Y


Seven-fold economic returns

The INCOSUR, IPA and IPCA initiatives were designed primarily as vector elimination pro-grams. At the time of writing, Brazil, Chile, Uruguay, and Guatemala have been formally declared free of Chagas disease transmission via their main vectors. Similar declarations have been made for various provinces and departments of Argentina and Paraguay. The distribution of T. infestans has been reduced from its predicted maximum of 6.28 million km² to under 1 million km² (see figure on page 15). Moreover, R. prolixus appears to have virtually disappeared from Central America except for a few remaining foci in Honduras. Also, in all countries of Latin America, screening of blood donors has been improved, with coverage close to 100% in most countries (except Mexico).

Disease detection and treatment

By contrast, the Amazon Initiative (AMCHA) – which includes parts of nine countries – was designed primarily as a surveillance program. This is because domestic vector populations are rare in most of the Amazon region (except for T. macu-lata in parts of Roraima and southern Venezuela). Instead, vector-borne transmission in the Amazon region is attributed primarily to adventitious silvatic bugs (mainly species of Rhodnius and Panstrongylus) flying into houses and contaminat-ing food and drink. Such transmission is often described as “oral-route transmission” and has resulted in a series of so-called “family microepi-demics” of acute Chagas disease in various parts of the Amazon region (and elsewhere). In such circumstances, there is little role for vector control programs. Instead, emphasis is given to detection and treatment of those occasional outbreaks of acute disease – a task where malaria slide-micros-copists are now playing an increasing role, by identifying trypanosomes in the peripheral blood-smears of febrile patients originally suspected of malaria. In a sense, the Amazon Initiative may also be revealing aspects of how the future of Chagas

TRIATOMINE BUGS as the insect vectors of Chagas disease can be eliminated in domestic settings by treating infested buildings.

Costs averaged around US$ 30 million per year for the Southern Cone, and around US$ 4-7 million per year for the Central American countries. However, studies in Argentina and Brazil indicate economic returns equivalent to over US$ 7 for every dollar invested in the Chagas disease control programs.6 Benefits have also accrued to those already infected, as clinicians throughout the intervened regions report reductions in the severity of chronic lesions.7 From studies in mouse models, such reductions seem to be largely due to lack of re-infection once the domestic vectors have been eliminated.8

Insecticide dose rates for Chagas disease vector control

SC = suspension concentrate; WP = wettable powder CS = capsule suspension (micro-encapsulated)

Deltamethrin Betacyfluthrin Lambda-cyhalothrin Alphamethrin Cyfluthrin Cypermethrin

Insecticide

Note that bendiocarb WP (400 mg a.i./m²) and malathion WP or fenitrothion WP (both 2000 mg a.i./m²) are sometimes used, mainly in parts of southern Bolivia and NW Argentina where some pyrethroid resistance has been recently reported in T. infestans.

Formulation Dose rate (mg a.i./m²)

SC or WPSCWP or CSWPWPWP

2525305050

125

Source: Schofield 1994, and WHO/CDS/WHOPES/gcdpp/2000.1

Photo: WHO/TDR/Stammers

C O V E R S T O R Y


disease control could proceed throughout the Americas, once the existing domestic vector popu-lations have been eliminated.

Widespread agent and vectors

A much debated question then becomes “Can Chagas disease be eliminated?” We must be clear on terminology: the causative agent, T. cruzi, will not be eliminated – it is a widespread parasite of small mammals and marsupials throughout the Americas. The vectors, Triatominae, will not be eliminated – there are over 140 species distributed in the Americas (and some also in India and SE Asia). As consequence, the disease will not be eliminated, in the sense that the ubiquity of para-sites and vectors in Latin America will always pose a risk of occasional transmission to humans. Such cases, without prompt diagnosis and treat-ment, can in turn pose a risk of onward transmis-sion through non-vectorial routes, such as blood transfusion, organ transplant, and occasional con-genital cases.

Eliminate domestic variants

But some vector populations can be eliminated: T. infestans over most of its original distribution in Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay and southern Peru; the central American form of R. prolixus, and the South American form – at least from the central valleys of Colombia; R. ecua-doriensis from northern Peru, and T. dimidiata from Ecuador. All these popula-tions appear

to have been imported – as domestic variants – from elsewhere, mainly by accidental carriage by humans, and mostly within the last 150 years. In a sense, their presence outside their original foci is aberrant, due to human accidents that should be corrected.

These populations have probably accounted for well over 80% of Chagas disease transmission, but they are not the only vectors. All populations of all species of Triatominae should be considered at least as potential vectors, although without human contact they can play no epidemiological role. So the focus perhaps should be to minimize that con-tact, and then to minimize the risk of that contact. With this perspective, outline strategies become clear. All existing domestic populations of Triatominae, of whatever species, should be elimi-nated, and experience accumulated from control trials and programs throughout Latin America show that this is possible (see box: Spraying procedures on page 11).

Now, how do we sustain this absence of domestic Triatominae, knowing that the previously infested houses may remain susceptible to re-invasion? The technical response was to improve insecticide formulations, in an attempt to give longer protection to the treated premises. But, recognizing that no treatment can last forever, the strategic response – as illustrated by the multinational initiatives – was to try to remove source populations, to make re-infestation unlikely. Successful when dealing with an imported domestic variant (such as R. prolixus in Central America), this strategy is much less successful when dealing with domestic populations that also occupy extensive peridomes-tic habitats (such as T. infestans in the Chaco region of NW Argentina and southern Bolivia) or that retain local silvatic ecotopes (such as T. dimidiata in parts of Central America).

The challenge of peridomestic control

The control of peridomestic populations of Triatominae is seen as a major technical challenge. Conventional spraying with WP or SC pyrethroids (as used inside houses) tends to have reduced

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C O V E R S T O R Y


impact, since the superficial deposits can be degraded by sunlight and/or quickly covered with dust or animal dejections. Some people report better results using a double spray9 or using slow-release polymer formulations.10 Others prefer physical modifications to the peridomestic habitat – for example, using higher standard fencing materials instead of piled brushwood for goat cor-rals in the Argentine chaco, which can greatly reduce the habitat available for peridomestic T. infestans and T. guasayana.11 Other approaches involve the concept of “xenointoxication” – treat-ing domestic animals with a pour-on or powder formulation of insecticide, in order to kill any bugs that may attempt to feed on them.12 Insecticide-impregnated dog collars have been used for a similar purpose13, and it seems likely that further technical developments will lead to improvements in the ways to control peridomestic Triatominae. But perhaps a strategic response also needs to be considered.

Combined with surveillance strategies

The importance of peridomestic Triatominae is primarily as a potential source for re-infesting the domestic habitat. Where possible, they should be reduced or eliminated, not least, for their effects on the productivity of peridomestic animals. But more importantly, from a public health standpoint they can also be viewed as akin to silvatic popula-tions, some of which are also potential sources for re-infesting the domestic habitat. Seen in this light, the strategy changes. It is both impractical and ecologically unacceptable to contemplate large-scale interventions against silvatic popula-tions of Triatominae. It is also irrelevant in terms of transmission control. Only by coming into con-tact with humans – for example by entering a house – does a silvatic bug assume possible epide-miological significance, either by causing direct transmission or by establishing a new domestic colony. But a newly established domestic colony can be eliminated, and a transmission event can be treated – which is the basis of the Amazon surveillance strategy. Perhaps even elsewhere,

peridomestic and silvatic populations should be considered similarly – focusing on the vectors only when incipient domestic colonization is apparent, but otherwise focusing only on diagnosis and treatment of possible new cases of infection.

The “end point” for elimination of Chagas disease as a public health problem can be then described when:

• All existing domestic infestations of Triatominae have been eliminated.

• Local health authorities are structured and equipped to diagnose and treat occasional new infections.

• Local health authorities eliminate – perhaps through contracts with local pest control opera-tors (PCOs) – any incipient domestic vector infestation.

Epidemiologically, the situation might then resem-ble that of Lyme disease in Europe – the vector ticks (Ixodes ricinus) are present in our garden (which may be said to comprise both peridomestic and silvatic habitats) and there is a risk of Borrelia transmission. However, the ticks do not enter our house, and if they did, would be rapidly dealt with, and if a new infection occurs it is relatively simple to diagnose and can be treated.

SPRAYING is an effective measure against Chagas.

Pho

to:

Bay

er

C O V E R S T O R Y


The data and experience gathered from differ-ent geographical regions of Latin America point to the combined strategies needed to eliminate Chagas disease as a serious public health problem. First, eliminate all existing domestic vector populations, and adequately incorporate all aspects of current control pro-grams into routine local health programs. The products, equipment, and experience are avail-able for this. Strategies have been developed both for the initial campaigns and their con-solidation through active vigilance, and for progressive incorporation of this surveillance into routine public health activities.

CONCLUSION

Article with references on the enclosed CD-ROM.

The political commitment

Although Chagas disease will not be eliminated, in the sense of ceasing to exist as a human disease, it could be eliminated as a serious public health problem – when all existing domestic vector popu-lations have been eliminated, and all aspects of current control programs are adequately incorpo-rated into routine local health programs. The prod-ucts, equipment, and experience are available for this. Strategies have been developed both for the initial campaigns and their consolidation through active vigilance, and for subsequent integration of the surveillance activities into routine public health activities.14

But all comes to nothing without political commit-ment and leadership, which in turn liberates the required resources. In a few countries there is still no coherent national program. In others the national program is in disarray, with spraymen and vehicles idle, since they lack the minimum resources to mobilize. Perhaps the initial successes of the multinational initiatives were too widely hailed. But relieving some 60 million people from the molestation of Triatominae and risk of disease (as some have claimed) still leaves some 40 mil-lion with little protection – which is both inappro-priate and questionable from an ethical point of view, given the demonstrated feasibility of the large-scale control interventions.

Paradoxically perhaps, a renewed urgency to com-plete the control interventions may come from the previously non-endemic countries now receiving migrants from Latin America. Some of these people require treatment for their chronic Chagas infection, and some pose a new risk for onward transmission by blood transfusion or organ trans-plant.15 It is to be hoped that the domestic Latin American vectors can be eliminated before they too begin to arrive in Europe and elsewhere.16

For ECLAT (European Community – Latin American Network for Research on the Biology and Control of Triatominae) and TVRC (Trypanosomiasis Vector Research and Control Foundation) please see page 57.

Reduced distribution of T. infestans

THE MAXIMUM DISTRIBUTION of T. infestans prior to large-scale control interventions is shown in pale grey, and corresponds primarily to domestic infestations – most of which have now been eliminated. The main areas where T. infestans can also survive in peridomestic habitats are shown in darker grey, and these currently also represent the main areas of residual domestic infestations.

Source: Schofield C.J. & Gorla D.E. (2009) Triatominae: Biology and Control. In: Human Parasitology (ed. W.Apt) McGraw Hill.



hagas disease is widespread throughout all of Latin America. Twenty-one countries are

considered endemic and at least 30 million people remain at risk of contamination. More than 13 million people are estimated to be infected by Trypanosoma cruzi, and about 30 percent of them are likely to develop severe Chagas heart disease as a result. Current estimates expect up to 15,000 deaths annually due to Chagas disease.

Systematic vector control

Prevention of human Chagas disease relies on the classical tripod of vector control, blood bank control and health education. This is then coupled with progressive improvements in specific and supportive treatment of those already infected. In Brazil, where the disease was first described by Carlos Chagas one

Chagas himself recognized that the most effective way to control the disease he discovered was through vector control. Systematic govern-mental programs since the 1980s have successfully decreased disease transmission in Brazil. Combining vector control with screening blood donors and medical care for infected people has drastically reduced the burden of Chagas disease. The chal-lenge is to maintain this.

Past successes and future perspectives

Chagas disease control in Brazil

century ago, systematic vector control was installed in the early 1980s. This was followed by an expanding program of blood bank control to

reduce the likelihood of transmission by trans-fusion from infected donors. Since then, all epidemiological parameters have decreased

progressively. This is in parallel with important demographic and social changes occurring in the country – particularly migration and urban-ization of rural populations, and the expansion

of larger-scale agricultural activities in previously endemic regions.

C

Phot

o: J

CPD

ias



Strategies for Chagas disease control

Even from his very first epidemiological observa-tions, Carlos Chagas realized that the most vulner-able target in Chagas disease transmission would remain in vector control. At that time (1910-12) Chagas also verified the possibility of T. cruzi transmission by a congenital (transplacental) route, but he could not confirm transmission by means of blood transfusion. This was only deduced by

All these factors have contributed to consolidating the advances achieved against domestic vectors. In Brazil, the peak incidence of transmission seems to have occurred between 1950 and 1970, reaching about 100,000 new cases per year. But now it is currently estimated that Chagas disease prevalence is between 1.2 and 1.7 million infected people. Morbidity is higher in central States such as Minas Gerais, Goiás and Bahia, with a greater concentra-tion of cases in the state of São Paulo (probably reflecting migration from other previously endemic states).

RURAL DWELLINGS were regularly checked for triatomine bugs by federal health agents in the 1980s, with a mean rate of 500,000 houses being sprayed each year (photo dates from 1983).



Salvador Mazza and Emmanuel Dias some thirty years later. Specific treatment of infected individuals was found to be extremely difficult, especially in chronic phase patients. Chagas and colleagues attempted treatment with anti-malarial, anti-leishmaniasis, and anti-syphilis drugs, but the first effective compounds – such as Nifurtimox – only appeared during the late 1960s.

Considering vector control, the first ideas emerged from Carlos Chagas himself, when in 1912 he began to promote the idea of housing improve-ment in endemic areas. This idea was followed up by his colleague, H. C. Souza Araujo, who studied the epidemiology of housing infestation in Paraná

State (Brazil) and proposed a law obliging the construction of safe rural dwellings in all the farms of the state (a law that was never enforced at all). The first insecticide tests against domestic Triatominae were carried out in 1921 in Belo Horizonte, Brazil, by Ezequiel Dias – another colleague of Chagas. In their laboratory, Dias and his collaborators tested several chemicals against Triatominae, scorpions, mosquitoes and cock-roaches, finding that sulfur gases were most effec-tive, but without residual action. Between 1944 and 1946, Emmanuel Dias tried other available chemical and physical tools against Triatominae at the newly-developed field site in Bambui, Brazil. These included cyanide gas fumigation, kerosene, NaOH solution, pyrethrum compounds, rotenone – and also heroic trials with a flame-thrower. From these pioneering trials, Dias reached two important conclusions: firstly, that control of Triatominae could be achieved in a domestic setting, and secondly, that the elimination of domestic bugs was followed by interruption of human Chagas disease transmission.

Eliminating domestic bugs

Following these observations, in 1946 Dias tested DDT (with poor results) and also Gammexane (γ-BHC, HCH), which proved to be highly effi-cient at killing domestic Triatominae and had a residual effect of 60-90 days. Similar results with BHC were also obtained by Romaña and Abalos in Argentina, and by Pifano in Venezuela using diel-drin. The decades that followed saw several fur-ther trials in Brazil (especially in the state of São Paulo), Argentina, and Venezuela, and also in parts of Chile and southern Peru, showing the rationale and good results of insecticide campaigns against Chagas disease. The best arguments to convince Latin American health authorities to fight against domestic Triatominae proved to have two main components:

• Epidemiological, revealing the widespread nature and severity of the disease.

• Operational, clearly revealing that elimination of the domestic vectors was feasible, safe, and highly efficient.

Much beyond the academic glory, it is mandatory to fight against this disease, regarding its complete elimination.

Carlos Chagas, 1934

“”



During the 1970s, the National Chagas Disease Control Program was devel-oped in Brazil, being followed by regional actions in Argentina, Chile, Uruguay and Venezuela. In 1974, again in Bambui, Brazil, the first regional initiative for epidemiological surveil-lance was tried, based on intense community participation.

Positive impact of vector control

By the end of the 1970s, the organochlorine insec-ticides were being phased out in favor of synthetic pyrethroids – particularly deltamethrin, but also cypermethrin, lambda-cyhalothrin and cyfluthrin – all of them showing identical action. Also, con-sidering the risk of possible pyrethroid resistance, a carbamate compound (bendiocarb) was tested, with satisfactory results. All the available pyre-throids began to be acquired by the Brazilian Public Health Department (SUCAM/FNS) through international tenders. At the peak of the vector control program in Brazil, between 1982 and

1986, more than 8 million rural dwellings were being regularly checked for triatomine bugs by federal health agents (SUCAM), with a mean rate of 500,000 houses being sprayed each year. Financial support for vector control came entirely from federal resources amounting to about 18 mil-

lion dollars, disbursed yearly by the Minister of Health throughout the National Agency for Public Health Campaigns (SUCAM). At that time, more than 5,000 federal agents were involved in the national program, with strict supervision of work quality and continuous actions in contiguous areas.

The impact of regular vector control was very positive in Brazil. In terms of macro-regional impact, the first results were seen in the state of São Paulo, where a state-wide campaign had been launched in 1966 under the state superintendency for endemic diseases (SUCEN). Here, serological screening among rural populations was already showing major reductions in vectorial transmission

The author: JOÃO CARLOS

PINTO DIAS

Oswaldo Cruz Foundation and Minas

Gerais Academy of Medicine, Brazil

• 1912 Developing an idea from Carlos Chagas, Cesar Guerreiro and Astrogildo Machado described the detection of anti-T. cruzi antibodies by means of a comple-ment fixation test (Bordet and Gengou technique).

• 1947-50 The first serological screening tests were achieved in the states of Minas Gerais and São Paulo (Brazil) among blood donors.

• 1950-51 The staff of São Paulo Univer-sity (Pedreira de Freitas and colleagues) developed a basic control strategy involv-ing serological screening of blood donors

The main tools and favorable strategies for control of transfusional transmission

and/or the chemoprophylaxis of suspected blood with Gentian Violet.

• 1960-80 Technical development of new serological techniques such as hemagluti-nation, immunofluorescence, and ELISA techniques.

• 1980s Emergence of HIV/AIDS, which stimulated blood bank control throughout the world.

• 1990s Intergovernmental Initiatives against Chagas disease launched in differ-ent parts of Latin America, based on vector and blood bank control.



by the end of the 1970s – in parallel with a dramatic reduction of domestic triatomine foci. At the national level, under SUCAM, the reduction in numbers of houses and communities with domes-tic Triatominae was also very impressive through-out the country, reaching a very low (<3.0%) proportion of detected foci by 1986. Considering the particularly good results against the main domestic vector, Triatoma infestans – whose elimination was foreseen by Emmanuel Dias in 1958 – areas reporting this species were intensively con-trolled. This meant that by 2002 it had virtually disap-peared except for residual foci in the states of Bahia and Rio Grande do Sul. Operational problems in these states were addressed, together with additional work against peridomestic foci in Rio Grande do Sul, resulting in the almost complete elimination of domestic T. infestans by the end of 2005.

Politics and sustainability

Through implementation of a regular national program, effective control of human Chagas disease is shown to be undoubtedly possible in Brazil – although the required actions must be sustained over several years. To reinforce the optimistic perspectives, some data registered in Brazil can be taken into consideration:

• From 1980 to 2006, the number of municipali-ties where any T. infestans was found, decreased from 711 to 2.

• The overall proportion of houses with any domestic Triatominae decreased from 25% (1980) to less than 2% (2006).

• The proportion of blood banks maintaining adequate serological screening of blood donors increased from 13% (1980) to 99% (2006).

• The proportion of candidate blood donors found to be infected is progressively decreasing (4% in 1980 to 0.4% in 2006).

• The risk of congenital transmission was already low, but is also tending to decrease because the number of infected fertile women is progres-sively decreasing.

• Clinicians throughout the previously endemic areas report improved prognosis for those people already infected – that is, fewer of the severest symptoms of the chronic disease. This may be due to a lack of re-infection, as well as improved patient care.

Multinational inter-government initiatives

From a public health per-spective, the main factors in this historic fight have been the expansion of vector control and surveillance activities, and improved

screening of blood donors, which is now under-way in most of the Latin American continent. A major achievement was the development of multinational inter-government initiatives against Chagas disease, beginning with the Southern Cone program (INCOSUR) launched in 1991. Through these activities, transmission of human Chagas disease has been drastically reduced, but residual foci still exist in some of the poorest and more isolated areas (and, it has to be said, in those few countries that have yet to develop a systematic national control program). In addition, we have a heritage of more than 13 million already infected individuals who require medical and social attention.

Maintaining disease visibility

For the next few years, the major challenges will be the maintenance of control and surveillance activities, together with adequate medical and social care for those already infected. The risk of occasional new cases will remain, partly as a result of congenital transmission, or oral transmission due to silvatic vectors contaminating foodstuffs, as well as some transmission where there are residual

Triatoma infestans



NGOs – such as MSF and DNDi, involved particularly in drug development, clinical and epidemiological research, and patient manage-ment, together with World Vision, Plan Inter-national, Pro-Habitat, promoting vector control and housing improvement in some of the most neglected regions.

International cooperation agencies – especially those from Japan and Canada, helping in program development, particularly in Central America and Peru.

Associations of Chagasic People – which represent the affected populations, offering pa-tient support, counseling, and also acting as foci for advocating better attention for existing patients in terms of diagnosis, treatment and case management facilities, as well as actively promoting disease control interventions. These patient associations were initiated almost 30 years ago in Pernambuco (Brazil) and now are present in several other parts of Brazil, notably Campinas, São Paulo, Londrina, Porto Alegre, Belo Horizonte, as well as in other countries such as Argentina, Bolivia, Australia, and Spain.

Institutions involved in combating Chagas

Health Education and Citizens Partici-pation – where this has been well developed, the community plays a vital role in epidemio-logical surveillance, both for the vectors and for detection of new cases. Much depends on the local authorities, and the national educational systems to bring knowledge about Chagas dis-ease and its vectors to the school children. But despite some excellent exceptions, relatively little has been done in this respect, which can be considered an important failure in the his-tory of Chagas disease control. Cooperation with industries* – both the pharmaceutical and pest control industries have been important partners in developing the large-scale programs against Chagas disease – not only for their support with demonstra-tion control trials, but also for their techni-cal advice, training, and support for planning activities. In addition, through agreements with WHO, the supply of both drugs currently used to treat acute and early chronic cases of Chagas disease has been assured – at zero or low cost. This tremendous help will sustain regular preventive and curative actions for very needy populations during five years or more, literally saving thousands of human lives.

foci of domestic vectors. All of these situations tend to decline if vector control and surveillance are maintained. Thus the greatest risk for Chagas disease in Latin America would be the decline in political commitment to continue control activi-ties. Currently, loosing disease visibility, other emerging health priorities and progressive weak-ening of technical, scientific and administrative

expertise must be considered the most crucial and negative factors facing Chagas disease control.

Another perspective however, is that the fight against Chagas disease has been gradually moved from strictly governmental and scientific hands, to involve new partners and protagonists. This con-stitutes a substantial advance, since new actors are welcome to reinforce and complement the fight

* See Bayer involvement on page 5



Article on the enclosed Public Health CD-ROM

The successes achieved so far in combating Chagas disease in Brazil reflect dedicated pro-grams by the government and more recently multinational initiatives. However, the chal-lenge is to maintain commitment to continue these activities before one can reach the defin-itive goal of disease control. New partners, political will, sustainable actions, better drugs, insecticides, diagnosis and vector control strat-egies are the present tasks facing all involved protagonists.

CONCLUSION

This reflection is dedicated to Carlos Chagas, Emmanuel Dias, Philip D. Marsden, Aluizio Prata, Carlyle Macedo, and Gabriel Schmunis

launched by Carlos Chagas one century ago. Four (five) main kinds of institutions have become involved with the traditional “chagologists” (see box on page 21)

The fight against Chagas disease can be consid-ered successful at the end of this first century since its discovery. Nevertheless, several challenges need to be faced in the next two or three decades in order to reach its definitive control. In particu-lar, there is a need for better cooperation between national governments and institutional partners, especially WHO and PAHO (Pan-American Health Organization), in order to sustain the famous Carlos Chagas dream, confided to his students and preferred follower Emmanuel Dias, at the end of his life: “Much beyond the academic glory, it is mandatory to fight against this disease, regarding its complete elimination” (1934).

1976 1995 1998 2002

Steps in the elimination of domestic Triatoma infestans from Brazil

Source: Brazilian Ministry of Health

2006: ELIMINATION of transmission due to T. infestans (certified by WHO/PAHO)



t their summit held in Lome, Togo, in July 2000, the African Heads of State and

Government considered the seriousness of the trypanosomiasis problem against a background of widespread reports of rising incidences of the disease and increasing infestation by the tsetse fly vector. Realizing that piecemeal inter-ventions would not yield a sustain-able solution, the African leaders agreed that the problem had to be tackled collectively on a continent-wide basis. They adopted a decision urging concerted action to embark on a Pan African Tsetse and Trypano-somiasis Eradication Campaign (PATTEC; see box on page 25). Under the general coordination of the African Union Commission, the PATTEC initiative seeks to mobilize new forms of organization, achieve new levels of commitment and insti-tute focused approaches. These should use available methods to address the tsetse and trypanosomiasis problem in a more systematic and sustainable manner, to eliminate the scourge of tsetse and trypanosomiasis once and for all.

Debilitating and fatal disease

In Africa, trypanosomiasis is a devastating disease caused by microscopic protozoan blood parasites called trypanosomes (genus Trypanosoma) trans-

The Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC) is a program of the African Union aimed at eliminating the scourge of trypano-somiasis from Africa. PATTEC coordinator John P. Kabayo describes the significance of trypanosomiasis as Africa’s most important neglected disease, as well as the strategies, plans and efforts by affected countries in imple-menting the PATTEC objectives.

Campaign against tsetse flies

PATTEC

mitted by tsetse flies (genus Glossina). The dis-ease afflicts man and livestock and occurs in 35 African countries, causing death, debility and diminished productivity. Trypanosomiasis (also known as nagana in livestock and as sleeping sickness in people) is a fatal disease for which no

easy treatment exists. If untreated, trypanosomiasis will kill its victim after a most horrific debilitating illness, during which the parasite invades the blood, the lymphatic system and finally the brain.

Until recently listed among Africa’s neglected diseases, trypanosomiasis is little known world-wide, but is arguably one of the continent’s most significant diseases. Few other fac-tors have had greater influence in shaping the continent’s history and ecological circumstances than try-panosomiasis. It is essentially a rural problem in Africa, where it is over-

shadowed by a myriad other critical emergencies. It blends with its own effects and consequences to become part of Africa’s tragic ecology and vicious circle of disease, poverty and diminished produc-tivity. It is widely recognized as one of Africa’s greatest constraints to socio-economic develop-ment, which has been responsible for untold human misery and massive economic losses.

A

The author: JOHN P. KABAYO

PATTEC Coordination Office, African Union Commission, Addis

Ababa, Ethiopia



This includes preventing or discouraging the development and use of animal traction power for transporting goods, ploughing the land and reliev-ing drudgery. The threat of trypanosomiasis forces most of Africa to stock low-productivity local live-stock breeds, which are relatively trypanotolerant and generally more capable of surviving infections of trypanosomiasis. In contrast, the more produc-tive exotic breeds easily succumb to the disease. Trypanosomiasis severely constrains meat and milk production and thus greatly affects nutrition and food security, and seriously hampers develop-ment activities in affected African countries.

Past trypanosomiasis control efforts

Africa’s colonial governments long recognized the importance of trypanosomiasis. During the period 1900 to 1970, they made extensive efforts and invested significant resources in fighting the dis-ease in different African countries, and in time, were able to effectively control it. Initially, the methods of tsetse control involved clearing the bush and vegetation where the tsetse flies rest, denying them shelter; and killing wild game ani-mals on which the flies fed. Later, other methods were used, including traps, targets and application

Socio-economic burden of trypanosomiasis

Trypanosomiasis claims tens of thousands of human lives and millions of livestock every year and threatens more than 60 million people in 35 countries in tropical and sub-tropical Africa. The disease and its threat have caused the depopulation of large areas of good pasture and agricultural land, and led to overcrowding in the limited tsetse-free areas. This causes competition for land and overgrazing, often resulting in conflicts and vari-ous ecological disturbances. Fear of contracting sleeping sickness and exposing their animals to nagana prevents people from living in tsetse-infested areas. The immense expanse of Africa’s potential farming land left uninhabited and unde-veloped because of the tsetse fly is often known as Africa’s green desert. This land is usually home to wild life, which not only provides a source of blood on which tsetse flies feed, but also serves as a huge trypanosome reservoir and a source of new trypanosome infections for people and livestock.

The threat and burden of trypanosomiasis on live-stock is one of the main reasons why most of Africa’s agriculture remains under-developed.

TSETSE FLIES INFEST about 10 million km2 of fertile land spread across 35 countries on the African continent, from Senegal in the north to South Africa in the south. Many areas that are infested with tsetse flies are the most suitable areas for livestock and crop production. These areas, however, are virtu-ally devoid of cattle and other domestic livestock. Therefore, out of the 165 million cattle found in Africa, only 10 million are found within the tsetse fly belt, and these are mostly low-producing breeds, which are maintained on high drug man-agement regimes to keep try-panosomosis in check.

Source: PATTEC

AFRICATsetse infested areas

Arrnox cattle distribution



of insecticides. During the 1940s, 1950s and 1960s campaigns involving habitat destruction and ground and aerial spraying of residual insecticides, including DDT, endosulfan and dieldrin, succeed-ed in rendering large areas in several African countries (notably South Africa, Nigeria, Kenya, Uganda and Zimbabwe) tsetse-free. At the same time, there were large-scale surveys and treatment of cases of sleeping sickness in people and nagana in livestock using trypanocidal drugs. These cam-paigns were extensive. Systematic, military-style operations were performed on a protracted basis throughout the colonial period. By the beginning of the 1970s, when most African countries had gained their political independence, the colonial governments had effectively brought the disease under control.

Tsetse fly re-infestation

Little or no attention was paid to trypanosomiasis by the regimes that came after the colonial period, largely because most post-independence African governments were generally pre-occupied with problems of state formation and other develop-ment issues. In most of the affected countries, trypanosomiasis became a neglected disease with no real action against it. In only a few other coun-tries was there any action, albeit limited and often ineffective. In general, the confident and deter-mined efforts employed in earlier campaigns, pursuing goals of tsetse fly eradication in large expanses of land, became replaced with approach-es whose objectives were merely to control or manage the disease on a limited scale. Since the 1970s, the activities mounted by various countries to address the tsetse and trypanosomiasis problem have been in the form of experimental, ad-hoc, uncoordinated and piecemeal efforts, which bore poor or unsustainable results.

The failure to sustain tsetse control operations and/or the inability to protect the treated areas usu-ally resulted in tsetse fly re-infestation. The devel-opment and growth of environmental conscious-ness since the 1970s led to withdrawal of the use of residual insecticides in tsetse control activities due to increasing concerns about the ecological

consequences of pesticide use, and contributed to increased tsetse infestation. The majority of tsetse intervention programs were donor-driven and invariably collapsed when the donors left, also leading to re-infestation in treated areas and nega-tion of the investments made.

Problems with drugs against trypanosomiasis

Furthermore, the use of the few available drugs to treat trypanosomiasis was fraught with problems of efficacy, toxicity, drug resistance, complicated

• Its negative impact on Africa’s health and productivity.• Its critical relevance to the continent’s struggle against hunger and poverty.• The limited or lack of action in the past against a background of reported re-emer-gence of the disease.• The problems of drug availability, effec-tiveness and safety.• The urgent need for a lasting solution and, given the technical feasibility and socio-economic justification for its eradi-cation.

The Summit of the African leaders adopted a collective decision to embark on a Pan African Tsetse and Trypanosomias Eradi-cation Campaign (PATTEC).

During the Summit of the African Heads of State and Government in July 2000, the African leaders consi-dered the trypanosomiasis problem, in particular:

PATTEC



administration and uncertain future availability. The early stage of trypanosomiasis, when the para-sites are still in the blood, is relatively easy to treat. Treatment of the late-stage of the disease when the infection has advanced considerably and the trypanosome parasites have invaded the central nervous system, however, requires the use of highly toxic drugs and often leads to patients dying from the drug rather than the disease. Melarsoprol, the only drug available to treat the late stage of the acute form of trypanosomiasis, was developed over 75 years ago. It is a highly corrosive preparation of arsenic suspended in anti-freeze, which is extremely toxic and burns the inner tissues of the veins when the drug is injected into a patient. Treatment is long and painful and requires nine injections, spread over three weeks.

Difficult treatment

No new drugs have been developed. The few drugs still in production have been rendered largely inef-fective by the widespread phenomenon of drug resistance, or are considered unsafe on account of their high toxicity. Further, the future availability of these drugs is uncertain. The four drugs regis-tered for the treatment of sleeping sickness (pent-amidine, melarsoprol, eflornithine and suramin) are currently provided free of charge to endemic countries through a 5-year agreement signed in 2001 and renewed in 2006 between the World Health Organisation and pharmaceutical compa-nies (Sanofi-Aventis: pentamidine, melarsoprol and eflornithine; and Bayer: suramin)*. It is not clear what the situation will be in 2011 when the current arrangement is expected to lapse. The lack of a convenient, effective screening test that is sensitive enough to indicate the stage of the dis-ease and guide the choice of drugs to use, presents one of the greatest challenges in the treatment of the disease. These difficulties are exacerbated by the complex nature of the treatment process, espe-cially in view of the remoteness of the trypanosomiasis endemic areas, which are charac-terized by poor infrastructure and weak or non-existent health systems.

Re-emergence of trypanosomiasis

Little by little sleeping sickness and nagana regained their hold on the continent; and by the late 1980s there was widespread consensus that tsetse fly infestation and trypanosomiasis inci-dences had reached unprecedented levels. The increasing incidences of trypanosomiasis, which were widely observed throughout the 1990s, gen-erated considerable attention and highlighted the need to question the persistent lack of government action in most of the affected countries. Against the background of recognizing that Africa’s popu-lation is growing at a rate that far exceeds the continent’s ability to feed itself and realizing that Africa cannot increase its agricultural production unless constraints, such as the tsetse fly, are removed, the widely reported escalating incidenc-es of trypanosomiasis generated a new sense of urgency and need for action. During the ensuing years, the great negative impact and effects of the

TSETSE FLY INFESTATION is one of the most important constraints to ruraldevelopment in sub-Saharan Africa. By transmitting animal trypanosomosis, thetsetse fly drastically reduces the numbers of livestock available.

* See article on page 5



threat and consequences of trypanosomiasis on the lives and livelihoods of millions of people among communities in Africa’s rural poor became a source of concern and put pressure on govern-ments in affected African countries to act.

Successful eradication on Zanzibar Island

In September 1997, after a 3-year pilot project, the eradication of tsetse and trypanosomiasis was achieved on the island of Zanzibar. The Government of Tanzania with support from the International Atomic Energy Agency, led a campaign that involved suppressing the tsetse fly population using conventional insecticide-based methods integrated with applying the sterile insect tech-nique (see page 38). Although this success was achieved on a small island with an area of 1,600 km2 infested by one species of tsetse (Glossina austeni), the eradication of trypanosomiasis from Zanzibar was an important historical achievement. It demonstrated the technical feasibility and via-bility of tsetse eradication as an effective interven-tion measure against trypanosomiasis. The achieve-ment was all the more significant because it came at a time when nearly the whole world was about

to adopt the resigned and pessimistic view that tsetse eradication was neither desirable nor achiev-able; being urged to accept the fatalistic option of living with the disease.

Declaring war on the disease

The decision by the African leaders to embark on PATTEC (see box on page 25) not only under-scored the seriousness and significance that African Governments attach to the tsetse and try-panosomiasis problem, but also defined their readiness to assume primary responsibility in implementing the objectives of the decision. The decision marked a significant departure from recent past practices, where the direct involvement of governments in tsetse and trypanosomiasis con-trol in the affected African countries was negligi-ble. Within the framework of this decision, the Commission of the African Union was charged with the task of initiating and coordinating the activities of the campaign. Every year it must report to the Summit of the African leaders on the progress made. This indicated that the affected African governments would be the de facto com-manders in a war that they declared against try-panosomiasis.

The Commission of the African Union was man-dated to remind Member States about their indi-vidual and collective obligations to implementing the objectives of the PATTEC initiative. Also, in collaboration with the affected countries, it was authorized to mobilize the resources needed to support the activities of the campaign. An office to help guide, organize and coordinate the activities for implementing PATTEC, was established at the African Union Commission. The PATTEC Coordination Office serves to increase awareness about the significance of trypanosomiasis and the necessity and feasibility of eliminating the disease. The office works with affected countries to gener-ate commitment and drum up support for imple-menting PATTEC. It generally seeks to ensure that the necessary effective action, aimed at eradicating trypanosomiasis, is initiated and sustained.

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In collaboration with countries affected by trypanosomiasis, interested national and interna-tional organizations and other partners, the PATTEC Coordination Office strives to bring together the political, financial and technical components of the PATTEC initiative and gener-ally tries to unite all participants in the campaign into one continental initiative.

Creating tsetse-free zones

Next, a Plan of Action to guide the implementation of PATTEC was developed by experts from the affected African countries. The PATTEC Plan of

Action is based on the systematic creation and expansion of tsetse-free zones. The plan outlines the approaches and methods by which the PATTEC initiative is organized and executed. The PATTEC initiative strategy involves identifying individual zones of tsetse fly infestation that are isolated physically, e.g. by mountains, water, or factors that limit the fly’s tolerance and preferences, such as food availability, climate, vegetation cover, etc. Alternatively, confinement of a target tsetse population can be achieved artificially by erected barriers. The tsetse fly infestation in such a zone is eliminated by applying principles of the area-wide approach using appropriate tsetse suppression methods (singly or in combination) to systemati-cally render each such zone tsetse and trypanoso-miasis-free. By successively tackling individual areas of tsetse fly infestation one at a time, and adopting quarantine measures to prevent re-inva-sion into treated areas, an ever-expanding tsetse-free zone is created. Sequential expansion in a rolling-carpet fashion to adjacent tsetse fly infesta-tions, should ultimately eradicate tsetse and trypanosomiasis in all affected areas.

The PATTEC program is executed in phased operations comprising a series of individual projects in identified areas. Each project area is selected based on the characteristics and criteria that define the extent or possibilities of its isola-tion, whether by natural or artificial means, such that areas rendered tsetse-free will be easily pro-tected from re-infestation from neighboring areas. Each project involves a series of defined activities, including preparing a project proposal describing the activities to be undertaken in each project area. This proposal covers all the steps, approaches and methods employed in the execution of the project and a carefully worked out budget and work plan. Thus each project is defined in space, time and resources.

Multi-national projects

Wherever cooperation or concerted action of neighboring countries is foreseen or required, as when the project area in question spans political

TSETSE FLIES transmit the parasites Trypanosoma ssp. that cause nagana in cattle and sleeping sickness in humans.

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boundaries, the necessary discussion is arranged under the auspices of the African Union. Within the framework of the PATTEC initiative, the modalities of cooperation in executing each multi-national project are agreed upon. Following prepa-ration of a project document for each identified project area, the process of mobilizing the neces-sary resources is undertaken by the affected coun-tries in close collaboration with the PATTEC Coordination Office and interested partners. The project activities are initiated as soon as the required resources are procured. These are sustained without stopping until the successful eradication of tsetse and trypanosomiasis from the

target area is achieved. As project activities prog-ress in the identified project area, efforts continue to identify subsequent project areas to be under-taken for which detailed project proposals are prepared and the required resources mobilized.

Large-scale actions essential

In the past few years, nearly all of the 35 countries affected by trypanosomiasis have developed plans and strategies for implementing PATTEC. Most

developing a human resources base to produce the cadres, technical and management person-nel involved in implementing the project, as well as arrangements to increase awareness among affected communities.

Ì Sustainable land management responds to the need to develop proposals for the sustainable use of tsetse-free land in view of the expected increase in use of land previ-ously rendered inaccessible by the threat of trypanosomiasis.

Í Project coordination and manage-ment: The operational unit within the PATTEC initiative is recognized at the level of manage-ment of an individual project. A project is defined by the sum of the actions necessary to render each specified project area tsetse and trypanosomiasis-free. In addition to the planning and supervision of activities in each project, activities of interest to PATTEC must be coordinated between and among other part-ners and stakeholders in each country.

PATTEC project components

Ê Tsetse fly suppression and eradica-tion involves the application of area-wide concepts, employing a phased strategy using an appropriately integrated combination of cost effective, environmentally friendly tech-nologies. These include insecticide introduced on targets or live baits or applied by ground or aerial spraying to suppress and eliminate the tsetse fly population in the project area. The sterile insect technique is an additional tool that may, if needed and available, be integrated with other tsetse suppression measures. Each project is preceded by baseline data collection to gather information on entomological, socio-economic, parasitological and environmental factors. This is used to fully characterize the project area and develop a comprehensive work plan to define and guide activities in project implementation.

Ë Training and capacity building pro-vides the knowledge, experience and skills needed for executing project activities. Since PATTEC is a new initiative, there is need for

To achieve the project objectives, each PATTEC project involves the following inter-related technical and support components:



countries have included trypanosomiasis control among their national development priorities. Several countries have initiated action on the ground aimed at tsetse and trypanosomiasis eradi-cation within the framework of the PATTEC pro-gram. Two countries, Botswana and Namibia have recently accomplished the objective of the PATTEC initiative and rendered their territories tsetse and trypanosomiasis-free; while a few other countries have not yet initiated any action.

The declared objective of the PATTEC initiative is to engage the action necessary and achieve eradi-cation of trypanosomiasis from Africa, through eliminating the tsetse fly vector, in the shortest time possible. Although tsetse eradication is tech-nically feasible, many affected countries have been unable to mount effective action because of constraints dictated by limited available resources, including the related budgetary difficulties. Such limitations afford only piecemeal operations in individual countries and prevent the harmonized multi-national actions necessary to address try-panosomiasis as a trans-boundary problem on a large scale. Indeed, lessons from past efforts to control the disease suggest that while tsetse con-trol must form the “primary objective” of trypano-somiasis control efforts, it must be tackled on a large scale or regional basis to avoid re-infestation. Operations must be carefully planned and executed methodically, progressively and continuously. The overriding problem is the enormous sizes of the areas to be covered. If the PATTEC initiative is to succeed, the methods employed must include a mechanism for effective, large scale, rapid and effective tsetse eradication.

Sequential aerosol technique

Botswana and Namibia, which in 2006 succeeded in achieving tsetse and typanosomiasis eradica-tion, have provided the most recent example of the feasibility of successfully attaining the PATTEC objectives. In the initial phase of this campaign, pioneering efforts of aerial spraying operations

succeeded in rolling back tsetse fly distribution (of Glossina morsitans centralis) from its southern-most limits in Botswana and Namibia. An area of over 25,000 km2 was tsetse and trypanosomiasis-free within 6 months. This success was achieved through the use of the sequential aerosol technique (SAT), involving the introduction of modified aerial spraying operations by the Botswana Government and the development of high-tech GPS-based track guidance and spray monitoring equipment using a highly effective, yet environ-mentally sensitive, insecticide formulation of the pyrethroid, deltamethrin. Notably, the impact of the insecticide on non-target species and the eco-system in the treated areas during these operations were shown to be minimal.

The sequential aerosol technique is now being widely incorporated into the strategic plans of other African countries as part of a concerted regional effort to manage tsetse and trypanosomia-sis. Angola and Zambia have just initiated aerial spraying operations in areas of their common tse-tse belt, bordering the tsetse-free zone in Botswana and Namibia. This followed a regional agreement

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TSETSE TRANSMITS SLEEPING SICKNESS, affecting a considerable number of people in Africa, thereby reducing the availability of labor as well as increasing the cost of health services.




Tsetse and trypanosomiasis eradication is tech-nically feasible, economically justifiable and socially desirable. The collective political deci-sion to eliminate the threat and burden of try-panosomiasis from Africa has been made at the highest level. A plan of action on the implementation of this decision has been pre-pared and adopted by all the affected countries. A continental structure to coordinate and pro-mote the activities of the campaign is in place. Two countries have successfully been rendered tsetse and trypanosomiasis-free; several others have initiated concrete action on the ground aimed at eradication and most countries have drawn their plans to engage in action. The campaign to achieve the objectives of the PATTEC initiative has been initiated and the war against the tsetse fly and the disease it transmits is now officially on.

CONCLUSION

signed between the four countries under the aus-pices of the African Union on cooperation in the eradication of tsetse flies from the Kwando/Zambezi region. Ghana will start aerial spraying operations in March 2010 and is likely to be joined by Burkina Faso with which they share a common tsetse belt.

Mobilizing resources and funding

African countries have risen to the challenge of eradicating trypanosomiasis and all the affected countries have demonstrated commitment to achieve the objectives of the PATTEC initiative. However, most of them are overwhelmed by many other health and development priorities and are severely constrained by limitations in the avail-ability of resources needed to support PATTEC activities. Against the long list of the continent’s critical emergencies, including HIV/AIDS, malaria, tuberculosis, conflicts, drinking water, roads and a host of other priorities, trypanosomia-sis does not always attract sufficient attention to warrant the necessary support and action.

There is therefore a need for vigorous advocacy to highlight the significance and negative impact of trypanosomiasis. Also, the African Union Commission has a duty to continuously remind affected countries about their obligations to imple-ment the collective decision to eradicate the dis-ease, particularly given the availability and feasi-bility of methods to eliminate the disease once and for all.

In addition, the African Union Commission has, in collaboration with the affected countries been try-ing to develop an enduring mechanism through which countries engaged in implementing PATTEC can receive support. In this regard, a group of countries (Burkina Faso, Ethiopia, Ghana, Kenya, Mali and Uganda) has received support in the form of soft loans and grants from the African Development Bank (ADB) in the first phase of the ADB-supported PATTEC program. A further 12 countries, which have been identified for funding in the next phase of the ADB-supported PATTEC

More

www.africa-union.org/Structure_of_the_Commission/depPattec.htm

program have recently developed tsetse and try-panosomiasis eradication project proposals. These will hopefully be supported so that project opera-tions can begin during 2010. Discussions led by the African Union Commission with other part-ners, including several Gulf States, China and Arab Bank for Economic Development in Africa, about supporting PATTEC activities are on-going. The Commission has so far organized two part-ners’ conferences to discuss plans for PATTEC activities in different countries and possibilities for their support. It is expected that all countries affected by trypanosomiasis will, by 2011, be engaged in concrete action aimed at tsetse and trypanosomiasis eradication.



ince the female tsetse fly breeds slowly, depositing one larva in a 10 day cycle, flies

must live for a long time – about seven weeks on average, with a maximum of about seven months. Hence, control measures that merely lower the birth rate are slow to reduce the numbers and spread of the flies. Given that the tsetse larva spends most of its life within its “mother”, and that tsetse pupae are well protected in the soil, attempts to kill tsetse must focus almost entirely on the adults. This can be done by habitat destruc-tion, i.e. bush clearing or shooting the wild hosts of the fly, but such procedures are unacceptable in the present age. Traps that simulate host animals can be poorly cost-effective, partly because they can catch only a small proportion of the flies attracted to them. The sterile insect technique

A range of methods to apply insecticides can and should be used in ways that best suit local conditions, land-use, geography, tsetse species, live-stock and ecology. The most important techniques include sequential aero-sol spraying, insecticide-treated cattle, and artificial baits such as traps and targets. Timing, coordination and combining methods are essential for sus-tainable control of tsetse fly infestation in Africa.

A very effective option

Using insecticides to control tsetse flies

(SIT; see page 38) is ecologically attractive and can eliminate small, isolated, single-species tsetse populations1 but the high cost and complexity of rearing large numbers of sterile males for each species in mixed infestations, makes SIT less suit-able than control measures that simply kill the wild flies, and deal with all species at once2.

Insecticides used against adults have been found to be the most appropriate means of tsetse control, especially since the slow breeding of tsetse counteracts possible development of insecticide resistance. The main points at issue are:

• Which method of insecticide application is most suited to each of the various circumstances of control operations.

• Implementation policy and planning. • Research to improve cost-effectiveness.

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depositing larvae, and the whole operation continues until all flies have emerged, then the population will have been eliminated. The low amounts of insecticide applied (e.g. deltamethrin applied at 0.3 g/ha) and the tsetse-specific timing of applications means that the method has minimal impact on the environment. The theory underpin-ning SAT is simple and elegant, but the technical challenge of killing every adult fly over an area of, say, 10,000 km2 on five separate occasions seems impossibly difficult. And so it proved: operations in Botswana and Zimbabwe in the early 1980s greatly reduced (>99%) tsetse populations but did not eliminate them3. However, the development of

GPS-based navigation systems have improved our ability to apply insecticide evenly, at an adequate dose, with the subsequent elimination of tsetse over areas of >10,000 km2. 4

The method is not a pan-acea however. First, the method is prohibitively complex and expensive, not only for livestock keepers but also for most NGOs and government agencies directly involved with control-ling trypanosomiasis.

Second, to ensure that the insecticide droplets descend to the ground, aircraft must fly low at night when atmospheric conditions are stable. Consequently, the technique can only be applied during certain seasons and in areas with relatively flat terrain. Third, the use of a non-persistent insecticide means that tsetse from adjacent, un-sprayed, areas can invade the sprayed block; a fast-moving species such as G. pallidipes can invade 25 km into the block within a year. Despite these drawbacks, the method has been used with considerable success in southern Africa, where ~40,000 km2 of Botswana, Namibia and Angola have been sprayed over the past decade.4

Ground spraying

The earliest insecticide-based methods relied on the application of persistent insecticides, such as DDT or dieldrin, to the natural resting sites of tsetse (e.g. boles of large trees). The insecticide was applied in sufficient concentrations to be effective for about three months, the time required to eliminate a population of tsetse. Ground spray-ing campaigns were extremely labor intensive, with thousands of spraymen walking through tsetse-infested habitats over areas of 2,000 to 10,000 km2 each year. Despite the success of the technique, concerns about the environmental impact of DDT, the method’s cost and logis-tical complexity and the emergence of new methods led to a decline in its use. There have been no large-scale ground spraying opera-tions for over 20 years, the last operation being in Zimbabwe in the late 1980s.

Aerial spraying

The sequential aerosol technique (SAT) relies on aerial application of a non-persistent insecti-cide that kills adult flies only. Since the insecticide does not persist in the environment, adults emerg-ing immediately after the application are not killed. Consequently, the area must be sprayed again ~12 days later, the precise interval being judged to allow as many adults to emerge from pupae in the ground but not so long as to allow them to deposit larvae in the ground. The process of spraying at ~12 day intervals continues for ~50 days, by which time all adults will have emerged.

In principle, if each application kills all adults, the timing between applications prevents tsetse from

S.J. TORR

Natural Resources Institute,

University of Greenwich, UK

G.A. VALE

Southern African Centre for

Epidemiological Modelling

and Analysis, Stellenbosch

University, South Africa

I. MAUDLIN

Centre for Infectious Diseases, College of

Medicine and Veterinary Medicine,

University of Edinburgh, UK

The authors:



Insecticide-treated cattle

Treating cattle with insecticide to control tsetse is not a new idea5 but the method became possible only with the development of pyrethroids.6 The method is especially appealing in several respects. First, treating animals with insecticide is simple and relatively cheap; many farmers are used to treating livestock with acaricides and this method of tsetse control simply requires a different active ingredient. Second, pyrethroids are effective against ticks and hence farmers can control a range of tick and tsetse-borne diseases using a single simple intervention; the obvious impact of deltamethrin on ticks provides a visible sign that the deltamethrin is effective, and hence contributes to uptake and sustained use of the method. Third, the problems and costs of maintaining artificial baits and preventing theft are reduced since live-stock keepers will naturally maintain and guard their livestock. While the method is cheap and simple, it was still beyond the means of poor live-stock keepers, especially when compared against the costs and simplicity of treating animals occa-sionally with trypanocides. Moreover, widespread treatment of animals can disrupt enzootic stability for tick-borne diseases and impact on non-target fauna.7

Recent research has tackled some of these mis-givings. Studies of the feeding behavior of tsetse showed that most flies attacking a herd of cattle, fed on the legs and belly of the bigger/older indi-viduals.8 Applying insecticide to the legs and belly of older cattle reduces the amount of insecticide used and impact on non-target invertebrates. Moreover, young animals remain exposed to tick-borne diseases, thereby allowing development of enzootic stability to diseases such as babesiosis and cowdriosis. This so-called “restricted applica-tion method” reduces the cost of vector control to ~US$ 2/animal/year, providing a simple, safe and environmentally clean method that is affordable and practicable for all livestock keepers.

But insecticide-treated cattle are also not the final solution for tsetse either: the spatial and temporal distribution of grazing and water, among other

matters, affects the distribution of livestock and hence insecticide-treated cattle may not be distrib-uted to control tsetse effectively. Moreover, cattle in areas affected by re-invading flies will still suf-fer trypanosomiasis since the insecticide does not prevent tsetse from biting cattle. Thus for livestock keepers living adjacent to, say, tsetse-infested national parks, treating their cattle with insecticide will not reduce the incidence of trypanosomiasis.

Insecticide-treated targets

Artificial baits consist of cloth screens, called targets, intended to represent hosts and coated with residual doses of pyrethroid. With the savan-nah species of tsetse the performance of targets is enhanced many times by adding the odor attractants identified in cattle, so that targets are effective at densities of around 2-4/km2. However, riverine species respond poorly to these odors, so that ten times the target densities are required.

Whereas cattle are patchily distributed, targets can be placed where they are needed, and hence they provide year-round protection against invasion from tsetse infested areas. However, such targets needed to control tsetse for several kilometers into the invasion sources are still too costly for poor farmers, so limiting the scope for public/private partnerships. Hence, biologists must lower even further the costs of target operations. The most important means of achieving this might be to discover additional odor attractants. For the main savannah species of tsetse, i.e., Glossina pallidipes and G. morsitans morsitans, it is known that when all identified attractants are dispensed at natural doses they are only half as attractive as live ox odor, so that at least one important attractant remains to be identified. Attempts to identify this attractant in the mid-1990s failed, but the technol-ogy for identification has improved since then so that another try is warranted. For the riverine tsetse we need to think again about the response to host odors. Since riverine flies respond poorly, if at all, to odors in experimental set-ups that show very



strong responses of savannah tsetse, the host-find-ing strategy of the riverine species must be differ-ent. Hence, distinctive set-ups may be required to test for the efficacy of odors.

New odors may not be the only route to better baits. Exploiting the visual responses of tsetse may provide new clues. A recent study9 with the riverine tsetse, G. fuscipes fuscipes, experimented with unusually small targets of only 0.06 m2, i.e., 1/16th of the standard size and a third of the size known to be disastrous for G. pallidipes. Surprisingly, the reduction of target size to 1/16th caused only a 50% reduction in catches of G. f. fuscipes. This has immediate practical implica-tions, suggesting that the cost-effectiveness of target control of G. f. fuscipes could be improved several-fold by using the tiny targets, even if twice as many are needed. Would tiny targets be effec-tive for other riverine species; how much further could target size be reduced; what is the optimal color and shape of small targets; are odors more effective when the visual bait is very small?

Traps/targets suffer from the economic problem of being “common goods” with the accompanying societal issues this can carry. While traps/targets may be effective as part of government/agency

funded control schemes, they may suffer from sustainability problems when affected communi-ties are left to deal with the traps themselves. We note that such “common goods” problems may be avoided by using insecticide treated cattle.

Policy and planning

CostsThe choice of application system depends largely on comparative costs. Tables of costs should be viewed cautiously since they can misleadingly compare techniques used for distinctive purposes under different conditions, and with various cost-ing procedures. Standardizing on the basic field costs of government-run clearance of an isolated population of savannah tsetse, the costs are estimated to be around US$ 380/km2 for aerial spraying, US$ 283 for artificial baits, US$ 56 for whole body spraying of 8 cattle/km2, and US$ 12 if application is restricted to the legs and belly.10 To these costs must be added overheads estimated at US$ 213-240/km2 for a full complement of administration, surveys, monitoring, ecological impact assessments and socio-economic studies. While the administrative and survey costs are unavoidable for sound planning and management, the other cost components are usually deemed

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AIRCRAFT SPRAYING to combat Tsetse infestation is a choice if the area is fairly flat and expansive.



necessary only with schemes run largely through governments and donor funding.

Hence, opportunities for cost reduction occur not only via the coordination of public and private attacks on adjacent infestations but also by part-nerships in which the private sector implements control in its particular area and governments may offer the minimum of specialist help with plan-ning, surveys and public health matters. Such a public-private partnership has been established in Uganda11 and has used the restricted application of insecticide to treat 220,000 head of cattle in five districts covering a total of 10,000 km2. In this scheme treatment expenses have been reduced to just two US cents per animal per month, even when private vets are paid to assist, resulting in field costs of around US$ 1/km2/year.

ChoicesGiven the indications for comparative costs, technical limits and seasonality of the various techniques, the ones to choose depend on the following principles:

1. If the tsetse population is not isolated, provide an invasion barrier of baits to produce isolation. Then, to eliminate the isolated population, put insecticide on cattle if these are present – pref-erably by public/private partnership if possible.

2. If cattle are not available, then: a) if the area is fairly flat and greater than about

1,000-2,000 km2, use aerial spraying, b) otherwise, use targets.3. If a campaign employs a mosaic of control

methods to suit varying terrain and land-use, apply the techniques to produce a synchronized effect, so that tsetse movement does not allow some flies to avoid treatment by any method. Natural and artificial baits are the most compat-ible since they can be applied at any season to work at similar speeds. Combining baits with aerial spraying may require the partial overlap-ping of treated areas.

Planning aidsWhatever techniques are used, their timing, loca-tion and intensity must be planned with a “feel”

for the population dynamics of tsetse. Problems resulting from the absence of such a feel are exem-plified by the aerial spraying of the 25,000 km2 of the Okavango Delta, Botswana, over 18 years from 1973 to 1991.3 Annual campaigns were piecemeal, with inadequate attention to the routes and rates of re-invasion. Hence, effects were poor until better planning in 2001/2002, with targets placed for an effective invasion barrier.4 To strengthen the prospects for good planning else-where we might encourage the use of user-friendly models of tsetse populations. For example, one such model has compared the cost-effectiveness of SIT and insecticidal methods2, drawn lessons from the results of the recent spraying and target cam-paigns in Botswana4, and helped to predict the costs of all control methods10.

Article and references on the enclosed Public Health CD-ROM

Insecticide-based interventions have achieved much over the past 50 years but the constraints of cost, environmental impact and sustainabil-ity have meant that progress has been less than hoped. These constraints are being addressed. For example, we no longer have armies of men applying large quantities of persistent organo-chlorines indiscriminately but, rather, livestock keepers applying small quantities of insecti-cides to sites where tsetse are most vulnerable. We are not reliant on a single method but have a range of techniques that can be applied indi-vidually or together to suit various circum-stances. Most encouragingly, we now have methods that are effective, cheap, clean and practicable, offering the possibility of vector control that can be applied and sustained by communities most affected by the fly.

CONCLUSION

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Space spraying and sterilizing tsetse traps

Space Spraying is a standard WHO recommended intervention for mosquito vector con-

trol in dengue fever campaigns and other arbo-viral disease control programs (see PHJ

19). Bayer Environmental Science was the first to prove a viable concept also for tsetse

control using thermal fogging with Cyfluthrine UL applied via portable machines (in

Uganda). Now, to prepare a portfolio suitable for all situations arising with the PATTEC

initiatives, boat-mounted fogging machines are being used to apply a deltamethrin con-

taining formulation in mangrove and riverine tsetse habitats (in Burkina Faso and

Equatorial-Guinea).

Concerning the treatment of tsetse traps and targets, Bayer Environmental Science is

following a different concept. Instead of controlling the individual flies approaching the

treated materials, both sexes are sterilized and released again into the environment. The

insecticide used is a so-called Insect Growth Regulator, normally used as a mosquito or

fly larvicide (triflumuron – Chitin Synthesis Inhibitor). Tsetse females that have been in

contact with a treated surface produce non-viable offspring. Even males coming in contact

with triflumuron on traps contaminate “clean” females with a sterilizing dose during

mating. With this delayed action and the effect on both sexes the vector population

decreases faster than by controlling individual pests. Other major benefits are the reduced

burden on the environment and a considerably lower likelihood of developing resistance.

Besides the standard applications of insecticides applied by sequential aerial spraying and the treatment of traps and targets with insecticides, Bayer is currently following new approaches in Integrated Vector Management.

New insecticidal approaches for tsetse control from Bayer Environmental Science

Please find an article on the sterilizing tsetse trap technique and initial results from Peter Langley, first published some years ago in Public Health Journal No. 10, on the enclosed CD-ROM



hree species of flagellate protozoa in the genus Trypanosoma cause sleeping sickness

in humans and nagana in livestock in 35 sub-Saharan countries. The trypanosomes are princi-pally transmitted by several species of tsetse flies (Glossina spp.) The tsetse and trypanosomosis (T&T) problem imposes an enor-mous burden on the affected countries. Estimates of over-all annual lost potential in livestock and crop produc-tion range from 1.95 to 4.75 billion US$ per year1,2,3,4 for nagana alone.

About 70 years ago three dif-ferent groups independently demonstrated that sterility can be induced in a target pest insect population by means of releasing insect pests5 but its expanded application against different species of tsetse flies was disputed. Over the years, though, the principle has developed into an ele-gant, efficient, specific and environmentally friendly pest insect control tactic (see box: Milestones of sterile insect technique (SIT) on the attached CD-ROM).

Today the sterile insect technique (SIT) is an acknowledged method for controlling and elimi-nating established populations and preventing re-infestations or new populations of major pest insects, including species of fruit flies, screw-

An insect pest population can be controlled or eliminated by releasing enough artificially sterilized males over several generations to induce high levels of infertility. Used successfully for a number of major insect pests, the questions are how, where and when this environmentally friendly technique can best be used to eliminate tsetse populations in Africa.

Using a pest to attack itself

The role of the sterile insect technique (SIT) in tsetse control

worm flies and moths6. Its application against populations of major insect pests has generated tangible direct and indirect benefits in developed and developing countries through reduction of

losses, access to profitable export markets, creation of labor, reduction of insecti-cide use and resulting environmental and socio-economic benefits.

Climatic and environmen-tal changes and expanded global trade favor the spread of insect pests and disease vectors. Preventing the establishment of inva-sive pests is a major con-

cern. Due to its inverse density dependence, the SIT is ideally suited for eliminating, in an environ-mentally friendly way, small outbreaks of intro-duced pests.

SIT must cover entire pest populations

Tsetse SIT requires factory-scale production of the flies and the reproductive sterilization of male flies, usually through gamma or X-ray irradiation. Following conventional suppression, enough sterile flies need to be released over a tsetse-infested area to outnumber the fertile males of the target pest population. Wild tsetse females that mate with the released sterile males (photo) will produce no off-spring. Conducting weekly aerial releases and

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maintaining a high sterile to wild male ratio over several generations of the insect pest can bring about elimination of isolated or confined tsetse fly populations.

In the past 30 years tsetse SIT experiments took place in Tanzania7, Burkina Faso8 and Nigeria9. An initial reduction of the target tsetse populations with traps or insecticides was followed by an SIT phase. The released sterile males induced high levels of sterility. In Burkina Faso and Nigeria the target tsetse fly populations collapsed in the treat-ment zones. Sustainable removal of the target tse-tse fly populations, however, necessitates treating the entire fly populations to their distribution lim-its. As this was not done in the above experiments, flies from untreated areas neighboring the SIT zone eventually reinvaded the project areas.

Successful SIT campaign

It was different in the mid-1990s on Unguja Island of Zanzibar10. Earlier efforts on the island to eliminate Glossina austeni, the only tsetse fly species on Zanzibar, by means of insecticide treat-ment of livestock and the use of traps and insecti-cide impregnated targets were unsuccessful. In spite of good initial fly population reduction and intensified suppression efforts, a relict population apparently “escaped” the control measures.

An integrated campaign involving a final SIT component against the entire distribution area of G. austeni on Zanzibar (see figure) made the difference: Since mid-1996 no flies have been captured, and the transmission of African animal trypanosomosis has ceased. Projecting from the findings of an earlier socio-economic assess-ment11,12, the accumulated benefits resulting from improved and expanded livestock and agricultural production on Zanzibar, meanwhile, will have exceeded the investments made for the integrated campaign.

This generated high expectations for expanded application of the tsetse SIT component in other T&T infested areas in Africa. However, some projects were designed to include the SIT compo-

nent without sufficient attention being paid to prerequisites for its application and to the feasibility of other control tactics alone or in combination.

Approaches to deal with the T&T problem

There are opposing “philosophies” on how the T&T problem should be addressed: to manage and live with the problem or to create sustainable tsetse-free zones. In the first case the T&T problem can be alleviated by means of localized, usually community-based, control measures that are restricted to farming areas. In contrast, in the second case area-wide integrated pest manage-

ZanzibarTown

Uzi Islandprimary forestsecondary forest

to Zanzibarairport

TuesdaysFridays, odd weeksFridays, even weeksTuesdays and Fridays

from Tanga

Mangapwani

Tumbatu Island

Kwebonaforest

Jozaniforest

Central Muyuniforest

Coastal Muyuniforest

*produced at a tsetse mass rearing facility in Tanga, mainland Tanzania

Flight lines on Zanzibar for aerial releases of sterile

Glossina austeni male flies*



ment (AW-IPM) targets the entire insect pest population, including both agricultural and wild-life areas. Localized efforts are cheap to initiate, but have to be maintained indefinitely if the bene-fits are to be sustained and the continual use of pesticides could lead to resistance, although this has never yet been seen in tsetse. AW-IPM on the other hand has much higher initial costs, but if elimination is achieved the benefits continue indefinitely without further cost.

Under an AW-IPM approach, for any particular situation the most appropriate intervention mea-sures are selected for application as part of the integrated, phased campaign. The SIT can be a component of an AW-IPM campaign13 but it is not suitable for a local-ized tsetse control approach.

Insects effectively find other insects

Tsetse control personnel know that initiating con-trol against untreated tse-tse populations usually leads to quick reduction of fly numbers. Many have also experienced that over time the observed sharp decline approaches a low level, at which the relict popula-tion stabilizes and no further reduction is recorded, even with increased control intensity. It is tempt-ing to translate data from an early phase of effi-cient tsetse reduction into simple mathematical models and then suggest that the selected control tactic alone will lead to elimination, without pro-viding proof in practice.

At reduced tsetse population levels, it often appears advisable to consider changing to or adding another control tactic, possibly SIT. Krafsur14 explains why an additional SIT component and not only the initially very effective control efforts should be

considered: “This is simply because released insects can find their wild cousins more effectively than can entomologists” with their monitoring and control efforts.

One criticism of the SIT for tsetse is that there are many species and each would have to be reared to produce sterile males. While there are more than thirty tsetse fly species and sub-species in the 8.7 million km² tsetse infested area about 30% harbors only one species and 87% contains no more than three tsetse species (see additional figure on the enclosed Public Health CD-ROM). The multiplicity of species, rather than being a hindrance, may be an advantage by breaking up the tsetse distribution into

smaller areas of the differ-ent species that can be eliminated one at a time. In some of these areas a SIT component may be considered.

Benefits of SIT

The application of the sterility principle in the past decades generated substantial benefits rang-ing from communities that found labor and opportunities in profit-able farming to national economies that had access to attractive export markets. Chilean apples,

Japanese melons, Mexican mangoes and tomatoes, Spanish citrus fruits and US and Central American livestock are proof of the impact of the SIT5.

It therefore would be unethical to deny Africa access to a technique that was and is so success-fully applied on other continents. South Africa already started successfully using the sterility principle against a variety of plant pests. The deci-sion to involve an SIT component as part of an AW-IPM campaign against the T&T problem, however, must be based on a careful and respon-sible feasibility assessment.

UDO FELDMANN

EntomologistInsect Pest Control

SectionJoint FAO/IAEA

ProgrammeInternational Atomic

Energy Agency

The authors:

ANDREW PARKER

Research EntomologistFAO/IAEA Agriculture and Biotechnology

LaboratoryJoint FAO/IAEA

ProgrammeInternational Atomic

Energy Agency



Phased planning and implementation

The Pan-African Tsetse and Trypanosomosis Eradication Campaign (PATTEC15,16) proposes a geographical step-by-step approach to establish and subsequently expand T&T-free zones (see article page 23). Each national or sub-regional campaign should proceed in a phased conditional manner in which subsequent phases are only to be initiated provided preceding ones were successful. The sequence under such an approach would be:

1. Policy and strategy development, long-term commitment: National policies and strategies need to declare the creation of T&T-free zones as a priority, requiring long-term commitment. Legislation, rules and regulations need to be in place, tailored to the special needs of an opera-tional AW-IPM program. Also, suitable manage-ment structures and efficient communication lines need to be established.

2. Baseline data collection: Available relevant information needs to be collated and additional baseline data need to be collected in a standard-ized manner, including entomological, para-sitological, socio-economic and environmental information. Some guidelines for standardized baseline data collection have been published17,18.

3. General technical feasibility assessment: In tsetse infested areas localized, normally community-reliant efforts help to alleviate the T&T problem but usually do not result in intensive area-wide tsetse suppression. Ground-based controls con-ducted by tsetse control staff are difficult to imple-ment over larger areas as they are logistically demanding (creation of access roads) and expen-sive19. Other tactics or a combination of methods need to be identified and approved, either to directly create a tsetse-free zone or to sufficiently reduce the fly population as needed to enable efficient implementation of the SIT.

In recent years the sequential aerosol technique (SAT) has been significantly improved in terms of effectiveness and environment-friendliness20.

Aerial SAT operations in 2001–2002, applied on an area-wide basis, have apparently eliminated Glossina morsitans centralis from the Okavango delta of Botswana and have subsequently been expanded into Namibia, Angola and Zambia21. Environmental investigations22 in Botswana and neighboring countries suggest no evidence of unacceptable environmental effects of the use of deltamethrin in SAT operations for tsetse control. Nevertheless, resistance to the incorporation of SAT as part of AW-IPM operations persists among many government authorities, donors and other stakeholders.

Candidate areas for tsetse elimination should be located at the edge of the distribution of the species concerned. If this is not the case, then the target area or target tsetse fly population must be isolated or very well confined with evidence that possible routes of re-infestation can be easily iso-lated in a sustainable manner. The interpretation of satellite-derived tsetse presence/absence risk prediction maps23, tsetse population genetics and geographic morphometric techniques can help to assess whether a target tsetse population is isolated.

If any of the above points cannot be confirmed, the creation of a sustainable tsetse free zone is not feasible and action against the T&T problem

TSETSE FLY FACTORY AT KALITI, ADDIS ABABA. Estimated capacity: 6–9 million female flies to supply sufficient sterile male flies to cover at least 7,000 km² of tsetse infested area at a time.

Phot

o: U

. Fel

dman

n, F

AO/IA

EA



Article, references and an additional figure* on the enclosed Public Health CD-ROM. Plus “Milestones of sterile insect technique (SIT)”*Areas infested with one or more tsetse fly species

The decision and initiation of efforts to create a tsetse-free zone – with or without a tsetse SIT component – need thorough feasibility assessment, considering technical and non-technical factors. Furthermore, such actions require high-level and long-term commitment. In several situations tsetse SIT can contribute to these efforts – in a mix of different interven-tion techniques that are applied as part of an AW-IPM approach. Tsetse SIT can be a power-ful, specific tool but is certainly no panacea or silver bullet for solving the T&T problem in all situations.

CONCLUSION

More

www.fao.org (search tsetse)www.iaea.org (search tsetse)www.africa-union.org (search PATTEC)

should remain restricted to localized T&T surveil-lance, suppression and treatment. Obviously, then, tsetse SIT would not be considered.

4. Other discriminating factors: Various relevant discriminating factors, trends or developments that either increase or reduce the feasibility need to be taken into account. The severity of the impact of the T&T problem should be ascertained, e.g. by a high demand for trypanocidal drugs. The potential of the area for agriculture and livestock develop-ment should be considered. The creation of T&T free zones needs to enhance poverty reduction, contribute to increased food security and maxi-mize socio-economic returns. Favorable climatic variations and trends can enhance T&T interven-tion measures.

5. Feasibility of AW-IPM without tsetse SIT: An assessment is needed whether one tactic or a com-bination of several techniques are likely to create a zone free of the T&T problem without involving a tsetse SIT component, as has apparently been the case in the Okavango delta of Botswana. Such assessments should be based on practical demon-strations in the field and certainly not solely on simple mathematical models with risky assump-tions.

6. Feasibility of an AW-IPM campaign with an SIT component: If case 5 above does not appear feasible, for example, when the area is too densely vegetated to use SAT for tsetse elimination or is insufficiently accessible to conduct large scale ground-based suppression campaigns, a tsetse SIT component may be considered.

The tsetse “SIT package” needs: a) sufficient, good quality and competitive sterile males; b) intensive area-wide pre-SIT tsetse suppression; and c) weekly aerial release capacity over a period of 18 months.

The increasing demand for tsetse SIT will neces-sitate, for the foreseeable future, the construction of large fly factories (see photo on page 41) at

suitable sites in Africa to hold some 50 million mass reared colony females in total. In addition several back-up or “seed” colonies of 50,000 to 100,000 females each will be needed.

When test releases and other entomological moni-toring activities confirm that the required level of area-wide pre-release tsetse population suppres-sion has been obtained, operational sterile male releases can begin as part of an AW-IPM program to create a T&T free zone.

A tsetse SIT component should certainly not be considered when: a) the area-wide suppression tactic itself is likely to easily lead to eradication in a cost-effective and environmentally acceptable manner; or b) there is no technically feasible AW suppression technique available and approved that would suf-ficiently reduce the target tsetse population as needed for the SIT phase.

M A L A R I A


nsecticide-treated mosquito nets (ITN) have been around for over 20 years and their efficacy

and effectiveness under various epidemiological settings proven for at least 10 years. But only in the last three to four years has implementation in malaria exposed countries reached or surpassed target levels of coverage (60-80% of households with at least one ITN) in a good number of coun-tries. We are beginning to see significant impact on malaria epidemiology, e.g. in Zanzibar, Bioko Island, Ethiopia or Rwanda. There are two major reasons for this change. First, the shift to massive public free net distributions either to young chil-dren and pregnant women or to the general popu-lation. Second, the firm establishment of long-lasting insecticidal nets (LN) as the standard ITN, at least for public distributions, but increasingly also in the commercial sector.

What is a long-lasting insecticidal net?

The term “long-lasting” refers to the effect of the insecticide on the net and not the net itself. That is why the term “long-lasting insecticidal net” is preferable over “long-lasting insecticide treated net”. And “long” means that this insecticidal effect is considerably longer than what can be achieved by a simple dipping of the net in an insecticide solution (conventional treatment) where the protective effect is lost after three to 12

Recent large-scale distributions of long-lasting insecticidal mosquito nets are bringing significant benefits in protection against malaria. But it is also crucial to know how long these nets last in the field. Many factors affect the useful life span of a bednet and they need to be assessed carefully in order to sustain the levels of coverage achieved so far. Also the economics of whether a net has to be replaced twice or three times within ten years plays an important role.

How long does a long-lasting insecticidal net last in the field?

Malaria prevention with insecticide-treated nets

I months of use. The criteria currently used by the WHO Pesticide Evaluation Scheme (WHOPES) to evaluate whether the “long” quality has been reached is that at least 80% of nets used in the field for three years must pass the strict criteria for mos-quito knockdown and killing*.

The principle of any LN is that a high dose of insecticide is applied in such a way that a small portion of insecticide is present on the surface of the net while the remainder is kept in a “reservoir” either within or on the netting yarn. As surface insecticide is used, washed or rubbed off or other-wise lost, it is re-established from the reservoir ensuring that the repellent or killing capacity against the Anopheles mosquitoes stays intact until all insecticide is gone. Currently two tech-niques are applied depending on the netting mate-rial. For polyethylene the pyrethroid insecticide can be directly incorporated into the netting mate-rial due to its low melting point and favorable dif-fusion characteristics. In contrast, for polyester a coating of some kind has to be used to serve as the insecticide “reservoir”. This coating or binding agent sticks firmly to the netting material and allows the shift of insecticide to the surface as

* Either ≥95% knockdown within 60 minutes or mortality ≥80% within 24 hours following a three minute exposure of Anopheles mosquitoes on the netting.

M A L A R I A


needed. To date six LN products have been recom-mended by WHOPES (see table above). Why is the “life” of an LN important?

From the very start of mosquito net use for malaria prevention the question of how long a net lasts has been discussed among experts. But until recently that question was not the focus of considerations, since the vast majority of nets were obtained from the commercial market and could be replaced whenever the users felt they needed to or had the funds and access to do so. However, with the scale-up of public sector distributions, most of which through mass campaigns, the question of when and how to replace these nets has become crucial for efforts to sustain the high coverage achieved initially. This has intensified the debate and led to the recently established notion that there are two kinds of LN, those with an average life span in the field of three and five years respec-tively. And many times it has been assumed that the former applies to the most commonly used polyester net of 75 Denier* and the latter to a poly-ethylene net of 150 to 180 Denier. Although there is no official WHO statement to this effect, the terms “three year” and “five year” LN have appeared in many working papers or documents going so far that some ministries of health have

issued statements that only “five year” LN should be used for public distribution.

In this situation it appears crucial to review the existing evidence regarding the life span of differ-ent nets under different conditions in order to shed some light on what we actually know and better define what additional research is needed. Even more importantly, we need to critically look at the concept of the “life” of the net, its components and determinants so that a common understanding is reached of what we are discussing.

Components of the life of an LN

A number of terms have been used to describe how long a net will last: net age, longevity, dura-bility, net “life” and “useful life”. The last term already indicates that some aspect of net usage or at least usability needs to be considered beyond the pure existence of the net. In the case of LN an additional major component has to be taken into account with respect to the “usefulness”, i.e. the duration of insecticidal protection, which is hoped to be at least as long as the physical net to make it a functional LN.

LN products currently recommended by WHOPES and some of their attributes

Net/Brand Material Denier g/9000m

Meshholes/inch²

Insecticide loading mg/m²

Olyset®

Duranet®

Netprotect®

IconLife®

Permanet 2.0®

Interceptor®

Dawa Plus 2.0®

Polyethylene

Polyethylene

Polyethylene

Polyester

Polyester

Polyester

150-180

145

100-115

75, 100

75, 100

75, 100, 150

75

132

136, 200

156-177

156-177

156-177

Permethrin 1000

Alphacypermethrin 260

Deltamethrin 63

Deltamethrin 55

Alphacypermethrin 200

Deltamethrin 80

* Denier is a measure of the linear mass density of filaments or yarn commonly used in the textile industry. It is defined as the mass in grams of 9000 meters of filament and describes the thickness of the material.

M A L A R I A


Physical “survival” of the net

We define the life of a net as the time from obtain-ing it until it is lost and needs replacement. We then consider the reasons why the net may be gone and the frequency of this event over time which is equivalent to its “survival” rate. On a population scale we describe net disappearance either from the side of the still existing nets, i.e. the proportion of nets given out that have been retained after time x (retention), or from the side of the nets no longer present (loss). The rate at which this happens at different time intervals fol-lowing the net distribution is the loss function (additional figure on the enclosed CD-ROM).

It is obvious, however, that evaluating the mere presence or absence of a net does not sufficiently capture the “use-ful” aspect of the net life, which implies that the net can be used for its purpose of covering the sleeper suffi-ciently to protect from insects. The net may still be present but in such a poor physical condition (torn, full of holes) that it can neither be hung nor cover the sleeping place. Or it has become unat-tractive to the user due to holes and/or dirt that he or she is hesitant to use it and eventually puts it either to other uses or away for good. Furthermore, the physical condition can prevent an effective protection even in the presence of insecticide if the holes are too many or too large. Therefore, the physical condition or integrity of the net has to be considered as a potential functional loss or “death” when evaluating its “useful life”.

Both components, net retention/loss and the phys-ical condition of the net include some behavioral aspects and it will be useful to look at these more closely (additional figure on CD-ROM). They can be divided into two categories or scenarios. First, the net “loss” may be intended by the user, i.e. the net is not wanted for a variety of reasons, given away to others (including being sold) or used for other purposes such as fishing or material for a wedding gown. This is usually referred to as non-

retention in the strict sense of the word. The second scenario is characterized by the loss of the net although the user has best intentions to use it. Being destroyed by fire is a clear example, being stolen another, although in this case the net may still benefit another person. One has to assume that the physical deterioration of the net is usually unintentional. Nonetheless, the care someone takes to protect the net from getting holes and repairing existing ones will significantly influence the dura-tion of its “useful life”.

Although intentional as well as unin-tentional losses may occur at any time it is likely that the former dominates the early losses. This par-ticularly applies following public distributions which may not always meet the exact preferences or may oversupply some families. The latter, namely physical destruction, is more prominent at the far end of the time axis. It is also intuitively clear that even with a given average “useful life” net loss will occur at all times. It is very likely to be slow in the beginning, when nets are new, as

well as at the end, when only few nets which are kept exceptionally well survive. The middle section of the loss function is more or less steep. Based on these hypothetical consideration and observations from phase III WHOPES studies on LN, the Malaria Consortium with support from the Swiss Tropical Institute has developed loss functions for two types of nets representing the three and five year average “useful life” (see figure on next page). These have been used in a model to project LN need and expected ITN coverage resulting from known LN distributions, but still need to be validated by actual data.

Currently available data on life of net

In general, data on net retention or loss and the physical condition of surviving nets is scarce com-pared to the overall literature on nets, ITN and LN. The best sources are the increasingly undertaken net retention and use surveys following large

The author: ALBERT KILIAN

Director Monitoring & Evaluation, Malaria

Consortium

M A L A R I A


These retention studies have also attempted to explore the reasons for loss of the net. Surprisingly, and against what some might have expected there is no evidence that selling the net is a significant factor at the household level. Most “lost” nets are either destroyed or given away to other family members out-side the immediate household.

Duration of insecticidal protection

If data on the life of the net is scarce, results on longevity of the insecticidal protection beyond one to two years of field use for the LN products shown in the table on page 44 is even scarcer. This is in part due to the fact that only two prod-ucts have been around for over five years: Olyset® and PermaNet®; and these also have received full recom-mendation by WHOPES. The others are still undergoing three year field trials and have an interim recommendation.

For Olyset® results are available from three, five and seven years of field use. Some of these studies have very small sample size and have been done before a standard field protocol had been devel-oped by WHOPES. They show generally sufficient insecticide protection, although in the CDC study in Togo the result after three years was borderline, with 72% fulfilling the criteria for an LN. The best studied product is clearly PermaNet® for which results from three studies and six countries are available with a follow-up of three years. In Uganda, Angola and Zambia 80% or more passed the WHOPES criteria, Togo was split with one study showing 83% passing and the other (the CDC study mentioned above) 68%. In Ghana the result was also borderline (75%) and in Madagascar only 50% of nets passed the criteria.

distribution campaigns. Data from nine published reports (Togo, Uganda, Sudan, Nigeria, Ethiopia, Mozambique and Kenya) and five unpublished surveys undertaken by the Malaria Consortium in Uganda and Mozambique seem to support the slow initial loss rate in the first 1-2 years (see figure above). Although data points for the type II polyethylene 150-180 Denier net are very few, they are in keeping with a slower loss rate of these nets. This figure also shows data from studies in Uganda, Kenya, and Tanzania that were either prospective LN studies with close follow-up of all nets, or observations in well defined project areas. All of the data points, for type I as well as type II nets, are beyond what would be expected if the median survival was three and five years, respec-tively. This observation supports the previously stated hypothesis that data from these sources are likely to be biased upwards and do not represent the average net survival.

MODELED LOSS FUNCTION for two net types, one with a 3 year (type I in red) and one with a five year (type II in blue) average survival. Data points represent data from net retention studies (red squares type I, blue squares type II). Green data points are indirect loss estimates by compar-ing coverage rates in two consecutive cross-sectional surveys in areas with minimal or no net input between data points, open circles represent prospective LN studies or data from smaller projects.

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Years

Pro

po

rtio

n o

f ne

ts s

till

pre

sent

in %

Loss function for two types of nets

M A L A R I A


This article is an excerpt from a longer contribution by Albert Kilian. Complete article including additional figures on the enclosed CD-ROM

It is important to establish standardized ways of assessing the useful lifespan of an LN in the field. Identifying factors that influence net durability, insecticidal activity, and loss can help planning strategies for replacing non-functional nets. This is essential for main-taining protection against malaria at both individual and community levels.

CONCLUSION

While there is significant variation from site to site, performance of polyester LN with coating technology seems to be consistent under the same conditions. In the ongoing phase III trials the Malaria Consortium is undertaking in Uganda the average rate of insecticide loss of three different products was almost identical, with 20-25% of the loading dose lost per year, leaving 30-40% after three years.

The factors that clearly influence the loss of insec-ticidal protection are washing frequency and regu-lar use and handling. Interestingly, the two coun-tries with the lowest results for PermaNet® in the WHO study (Madagascar and Ghana) were also the ones with the highest washing rates. Whether or not, and if so, to what extent temperature or humidity and dirt on the net contribute to insecti-cide loss is still under debate and no clear results are available yet.

What does this mean for malaria prevention with ITN?

The first conclusion clearly is that more work needs to be done on many aspects of the “useful life” of an LN under field conditions. These include:

• Agreement on a standardized way to measure the physical condition of nets, and its applica-tion to study the correlation of physical condi-tion and usage and/or effective protection, to better identify the point at which a net ceases to be useful.

• Use of combining examination of currently present nets and a history of previously owned nets to more clearly define the average life of various net types.

• Direct comparison of nets of different materials and yarn qualities in the same setting and over longer periods of time to identify the factors that influence net durability the most.

• Identification and quantification of factors other than washing and handling that may influence loss of insecticidal activity.

Secondly, from the available data to date it can be concluded that the loss of nets for various reasons

– and therefore the need to replace them – is a continuous process with a non-linear decline. This implies that repeated mass campaigns every three or five years are most likely not an optimal solu-tion. Wherever possible net replacement should be done through continuous delivery strategies. Where this is not possible mechanisms have to be developed that will allow a demand driven distri-bution algorithm, i.e. replace those nets that need replacement.

Finally, from the limited data on the insecticidal activity under field conditions it is evident that a few nets will always fail before the physical net reaches the end of its “useful life”. While it is questionable whether this will lead to a failure of control programs at community levels given the mass effect at high coverage levels, it nonetheless implies that some net users will have reduced pro-tection and this question needs to be addressed.

TYPICAL HOLES observed in polyester nets (75 Denier).

M A L A R I A


eginning during World War II, IRS has a long and distinguished history in malaria control.

Thanks to IRS, malaria was eliminated as a public health problem in the 1950s and 1960s in large parts of Asia, Russia, Europe and Latin America. Millions of humans owe their life and prosperity to the regular application of insecticide in their home. In the light of these massive successes, the

Currently, the best tool for the prevention of malaria in sub-Saharan Africa remains vector control using insecticides. Two approaches have been used successfully so far on a large scale: insecticide-treated nets (ITNs), and indoor residual spraying (IRS). The following report weighs up factors such as cost-effectiveness and impact on malaria transmission for both of these strategies. It also explores how the move to long-lasting insecticidal nets (LNs) can improve efficiency and allows cost-savings, e.g. per year of protection or treated net year, and may enhance the reach and sustainability of vector control activities.

Cost and effects of large-scale vector control

LNs and IRS

I N S E C T I C I D E - T R E A T E D N E T S

historical perception that the malaria eradication phase from 1955 to 1969 was a failure must be seen as one of the greatest public health communi-cation disasters of all times.

At present, IRS is still used on a wide scale and many countries in Latin America, Central and South Asia would see a rapid return to intense

B

Photo: Bayer

M A L A R I A


development, with first large-scale field trials dat-ing back to the late 1980s. Since then, the malaria impact of ITNs has been well demonstrated in over 120 settings worldwide, with no less than 22 randomized controlled trials in all endemic set-tings. Emerging evidence of impact from national-scale programmes confirmed trial results in every situation. A Cochrane review* first published in 1998 has provided a solid basis to assess impact: In highly endemic settings the systematic use of ITNs prevent 5.5 deaths per 1000 children pro-tected per year, and prevents about half of all the clinical episodes.3

Benefits of malaria control

Following the creation of the Roll Back Malaria Partnership in 1998 the control of malaria has seen a major revival and many positive developments have taken place. Firstly and foremost, the global interest in malaria control has substantially increased, to the extent that the humanitarian ben-efits of insecticide-treated mosquito nets have become a topic of discussion in the social circles of New York or London. IRS has been promoted

malaria transmission if IRS was discontinued. In the potentially highly endemic countries of south-ern Africa, over 13 million people are currently protected by IRS and experience a very low risk of acquiring malaria.1 However, while nobody doubts the impact of IRS in a wide range of transmission situations, evidence for impact according to accepted epidemiological standards is scarce. A recently completed Cochrane review* on IRS impact2 highlighted the low number of high-quality randomized controlled trials. As a result, providing high-quality and properly quantified evidence of health impact is impossible at present. In many ways, IRS was so effective in reducing malaria transmission and disease that few scientists felt the need to measure that effect systematically.

By comparison, there is plenty of excellent evi-dence on the health and transmission impact of ITNs. This intervention is a much more recent

I N D O O R R E S I D U A L S P R A Y I N G

* Cochrane reviews investigate the effects of interventions for prevention, treatment and rehabilitation in a health-care setting. See: www.cochrane.org

M A L A R I A


as a human right in many articles in the world press. Celebrities speak out publicly on the burden of malaria affecting the poor of the world. This increas-ing attention has been mirrored by an extraor-dinary positive trend in funding. Exact figures are difficult to compile, but while only tens of millions of dollars were available for vector control in the 1990s, invest-ments have crossed the one billion dollar barrier in the past two years. Much of this is accounted for by the Global Fund to Fight AIDS, Tuberculosis and Malaria, the US President’s Malaria Initiative and the World Bank Malaria Booster Programme. Increasingly, malaria control is seen as a produc-tive investment rather than an expense, and the private sector is also discovering its benefits and plays a fundamental role.

In this period of extraordinary developments and opportunities the question as to how best to spend these new resources in the medium- and long-term remains an important issue and the object of many public and private discussions. With regard to vec-tor control, the decision as to which method to use in a given situation requires weighing up not only the effectiveness of the two interventions, but also the local epidemiology, the costs, as well as other factors. The latter include the ability of the health system to implement the intervention, and levels of insecticide resistance. Some of these elements are reviewed below.

Do ITNs or IRS work best?

While the impact on malaria transmission and the associated positive health impact of both IRS and ITNs are undisputed, there is remarkably little good quality comparable evidence. A review con-ducted in 2003 by the Swiss Tropical Institute and

the Medical Research Council in Durban suggested that both approaches were very similar in terms of their health effects.4

This was confirmed recently with a Cochrane Review on IRS.2 While not based on solid epidemio-logical evidence, this conclusion seems rea-sonable in the light of

our current understanding of how ITNs and IRS operate. When making comparisons, care should be taken to always compare both approaches at maximum coverage level. To some extent the transmission effects of ITNs are underestimated because in many settings coverage is high in children (who experience high malaria mortality and morbidity and hence receive preferential pro-tection) but low in the rest of the population. This is unlike IRS, which is always implemented with a targeted high universal coverage. With the gener-alization of the universal coverage strategy for ITNs it is likely that the transmission effects of both interventions will be similar.

Health system effects and malaria epidemiology

The scaling up of malaria vector control activities provides unique opportunities and challenges for health systems in Africa. On the one hand, preven-tion of malaria leads to a drastic reduction in the number of patients in health facilities, easing the burden on over-stretched facilities.

On the other hand, comprehensive vector control programs can burden weak health systems and lead to new problems. In general, ITN programs with their range of strategic options and possible support by non-health sectors are more flexible in their demands on the health system. In addition, the new generation of long-lasting insecticidal nets (LNs) has an antivectorial effect of three to

The authors: CHRISTIAN LENGELER, JOSHUA YUKICH

Swiss Tropical Institute, Basel, Switzerland

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five years and possibly more. This compares favorably with IRS, which has to be repeated in the best case once per year. In areas of perennial (all-year) transmission IRS might even have to be applied twice per year, especially if the political, ecological or resistance situation requires the use of shorter-lived insecticides such as carbamates or organophosphates as opposed to long-lasting pyre-throid formulations or DDT.

By contrast, in epidemic-prone zones, IRS may have significant advantages over the use of ITNs because it can be restricted to periods in which there is a clear risk of an epidemic. This avoids delivering an intervention at times when mosquito levels and transmission risk are minimal. A posi-tive side for IRS is also that it relies less on com-pliance by the population, which can be an issue with ITNs. Finally, IRS currently offers a much wider choice of insecticide classes than LNs, for which only pyrethroids are suitable. Hence, IRS could become an important strategic option when dealing with extensive resistance to pyrethroids.

Which approach is most cost-effective?

From a cost and cost-effectiveness perspective, ITNs have been much more closely investigated than IRS, especially in recent times. Unfortunately, many of the available studies display a marked heterogeneity of methods, scales, scopes and out-come measures, making direct comparisons between the various ITN costing studies difficult.5 In addition, most such studies were based on the implementation of small projects, making the gen-eralization to national scales questionable. An important consideration is also that ITNs can be implemented in a number of ways, and different strategies bear different costs per person protected.

Recently, several standardized national or large scale cost measurements for ITNs have become available: in Malawi (highly subsidized nets dis-tributed mainly through maternal and child health clinics), Togo (integrated free LNs campaign to children), Tanzania (pregnant women vouchers and commercial sector distribution), Senegal

EritreaTogoMalawiSenegalTanzania

KwaZulu-NatalMozambique

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Average annual cost per LN distributed

Cost per* Cost per death averted

Indoor residual spraying (IRS)

Long-lasting insecticidal nets (LNs)

Average annual costs for LNs of 5 years duration and IRS in selected countries (2005, US$)

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(commercial sector approach with some subsidies) and Eritrea (entirely public health distribution). For IRS, large-scale costing was performed for two sites: KwaZulu-Natal, South Africa, and the Lubombo Spatial Development Initiative (LSDI) in Southern Mozambique.

An overall re-analysis and comparison of these data was completed in 20086, allowing for the first time to compare the main ITN implementation strategies, as well as providing comparative data between ITNs and IRS. Because setting-specific health impact data were not available, the analysis assumed that ITNs and IRS had the same health impact (derived from the existing ITN Cochrane review).

Conventional ITNs: The cost per treated net-year of protection ranged from US$ 1.21 in Eritrea to US$ 6.05 in Senegal. The cost per child death averted ranged from US$ 998 to US$ 2,926.

Indoor residual spraying: The cost per person-year of protection for all ages were US$ 3.27 in KwaZulu Natal and US$ 3.90 in Mozambique. The cost per child death averted was higher than for conventional ITNs: US$ 3,933 in Mozambique versus US$ 4,357 in South Africa (see table on page 51).

Long-lasting insecticidal nets: The usage of long-lasting insecticidal nets (LNs) of three years duration (and a cost of US$ 5) led to lower opera-tional costs: the cost per treated-net year of protection ranged from US$ 2.04 in Malawi to US$ 4.14 in Senegal. As a result the cost per child death averted ranged from US$ 743 to US$ 1,503.

The usage of LNs of five years duration (and a cost of US$ 7) led to even lower operational costs: The cost per treated-net year of protection ranged from US$ 1.69 in Malawi to US$ 3.25 in Senegal. As a result the cost per child death averted ranged from US$ 692 to US$ 1,181 (see table).

Very clearly, vector control interventions represent a tremendous public health investment, just only slightly higher than childhood vaccination.

Article (with references) on the enclosed Public Health CD-ROM

While the decision as to which strategy is best in a given setting must be made considering many of the factors outlined above, the current evidence suggests that LN programs are more cost-effective than either conventional ITNs or IRS in high transmission areas. In contrast, IRS programs have advantages in epidemic-prone zones and in areas with high levels of pyrethroid resistance. In any case, all vector control approaches are extremely good public health investments. Finally, a question often raised, especially in view of the recent call for malaria elimination, is whether carrying out both interventions together would be better than either alone. Unfortunately, there is virtu-ally no evidence to answer this question at present and this represents a high priority for research.

CONCLUSION

This article was written in memory of Chris Curtis, whose contribution to vector control has been so important.

Another important finding is the clearly better cost-effectiveness ratio for LNs compared to either conventional ITNs or IRS. Despite a higher initial investment, the overall efficiency of vector control improves with LNs. Having to repeat a net distri-bution less often also represents a tremendous operational advantage for many remote rural loca-tions in sub-Saharan Africa. Finally, this might be the only way to offer effective vector control services in politically unstable areas with poor security, where a ceasefire might be arranged from time-to-time and LNs distributed alongside other health interventions such as vaccines and vitamin A.

None of the programs examined in this study were financially sustainable, with the exception of the South African IRS programme. This is a strong signal that international funding for malaria vector control, while an excellent investment, will have to continue for a long time to come.


alteser International, evolv-ing from Malteser Germany,

was set up as the Order of Malta’s global relief service for humani-tarian aid in 2005. It is engaged in 200 projects in about 20 coun-tries worldwide. The organiza-tion provides not only emergency relief, but also promotes primary health care services and imple-ments measures for sustainable development.

A neglected disease

While major funding and aware-ness raising programs have recently focused on malaria, HIV/AIDS and tuberculosis, many other tropical diseases cause major suffering in the

world (see PHJ No. 19: Neglected Tropical Diseases). Moreover, climate change and international trade and travel could spread these diseases to new areas (see PHJ No. 20: Climate change).

Plague is still an ominous disease in parts of the Democratic Republic of Congo. In the territo-ries of Mahagi and Aru it is endemic and dangerous, threat-ening the lives of some 650,000 people. Although bubonic plague is a major health hazard, pulmo-nary plague is usually fatal. This is an ongoing threat that haunts these people all their lives. Many have lost relatives or neighbors to the plague.

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Between July 2007 and June 2008, Malteser International in Mahagi set up a cooperative proj-ect financed by US$ 357,835 from the DR Congo Pooled Fund. Right from the start the aim was to provide free medical care to plague patients and free prophy-lactic treatment to contact per-sons. It also involved working together with local health agents and local village committees. This funding was then extended for a further six months.

Rapid response essential

Time is always essential because early, correct and complete treat-ment is the only way to save

Plague cases treated

Contact persons receiving prophylactic treatment

Nurses refreshed in diagnostics and treatment of plague

Laboratory assistants retrained

Members of village committees trained for epidemic response

Village committees for epidemic response newly equipped

Huts treated with insecticides

Results of the program (from July 2007 to June 2008)

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Malteser International: Fight against plague in the Democratic Republic of Congo

Optimizing intervention strategiesBy combining free medical treatment with awareness raising, surveillance, pest control and training, the project in DR Congo aims to stop local outbreaks of plague. Not in the public focus like malaria and dengue, this neglected tropical disease is a severe threat in some parts of the world.

MALTESER STAFF DISTRIBUTING spray equipment, protective clothing and the insecticide deltamethrin to the local committee from Nyarambe.

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plague patients. When an out-break occurs, part of the rapid response is to rush free drugs to the appropriate health center. Then the situation is evaluated together with local health agents. Nurses in the health centers are given a quick on the spot refresher course in diagnostics and treat-ment of plague according to national protocols. And labora-tory technicians in the region are also trained in diagnostics.

During previous projects com-mittees for epidemic response were created in the 11 endemic health zones. Their task is to raise awareness about the disease in their villages. Activities such as flyers, posters and radio spots encourage the people to bring every suspected case to the health center, where treatment is free. Epidemic response committees were also trained in spraying techniques, and upon news of an outbreak they are supplied with pumps, protective clothing and insecticide. They then spray the huts of plague patients and sur-rounding areas to kill the fleas and prevent further transmission.

Preventing panic

Stopping transmission is a very important part of the strategy, because any outbreak of plague, particularly pulmonary plague starts to spread panic among the local inhabitants. Remaining

SAMPLES ARE TESTED for the plague by Malteser staff using a new rapid diagnostic test.

MEMBER OF A VILLAGE COMMITTEE spraying the hut of a plague victim. He starts with the earth floor and then works up the walls.

rational, and reminding people of good and bad practices, such as avoiding close contact with the dead and not washing the victim’s body for the funeral, can help prevent further transmission.

Study confirms good knowledge A study in northern Ituri, financed by the DR Congo Pooled Fund, asked a wide range of local people various questions about the plague. In this joint effort, Malteser International drafted the questionnaire and then together with IPASC (Panafrican Institute for Community Health) collected and analyzed the data. The aim

was to find out how much people in the area know about the dis-ease, such as its symptoms and how it is spread. They were also asked about their attitude to the disease and how they react in the case of an outbreak. All this information was compiled to assess what aspects future inter-vention projects should focus on.

In general the people knew quite a lot about plague, how fleas on rats spread the disease, and even how to prevent it, for example by using rat poison or keeping cats. But they lacked coherent ideas about what to do in practice over the long-term. The vast majority would take someone in their fam-ily with plague symptoms to a health center or hospital. Most of them were very positive about joining the fight against plague, adopting behavior changes and taking part in local activities.

Both the program for fight-ing plague and the statistical study show that the work being done by Malteser International is very success-ful and greatly appreciated by the local people. But they need and want more infor-mation and encouragement to take up activities to con-trol this disease.

CONCLUSION


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ver half of the 30 million people in Uganda are

younger than 16, and two mil-lion of these children are AIDS orphans. The country also suf-fers from extreme poverty, malaria and HIV/AIDS, malnu-trition, high mother and child mortality, poor medical care and limited chances for education. Care and education

Recognizing this tremendous need, Emmanuel Musoke and his wife Maria Goretti Namuyomba,

Centered around a project for AIDS orphans in the region near Masaka in Uganda, “Our Children and our Future e.V.” promotes various activities. In addition to helping children attend school, it sets up initiatives to improve medical care, and malaria prevention by distributing and ensuring proper use of mosquito nets.

Giving people a chance

“Our Children and our Future e.V.”: Support for a self-help project in Uganda

a qualified nurse, started a self-help project in the year 2000. Musoke lived in Germany for a while. Upon returning to his homeland, he and his wife started looking after orphaned children from the villages of Nyendo and Kamukongo who had lost their parents to AIDS. They provided them with food, a home, health care, and the chance to attend school.

Emmanuel and Maria found support for their project through contacts in Germany. The orga-

nization “Our Children and our Future e.V.” was founded in Remscheid. This supports the self-help project in Uganda with sponsorships and donations, such as paying school fees for children living in nearby villages.

Mosquito net goal successful

Of course the project also aims to ensure adequate health care for the children, families in the community and local people working for the project. With this goal in mind, the physician Dr. Helmut Cuntze accompanied Franz Lebfromm from the Remscheid support organization on a trip to Uganda in 2009. Dr. Cuntze visited the hospitals in Kitovu (on the outskirts of Masaka) and Villa Maria (near Kamukongo) to assess the medical situation (see box on page 56).

Following their visit, the first important goal to improve condi-tions at both hospitals was successful. In addition to 60 bed-nets for the children’s project, Bayer Environmental Science donated a further 450 impreg-nated mosquito nets to protect all the hospital patients and staff from malaria.

Other ways of helping the com-munity include setting up work-shops and small businesses, such as an Internet café, computer training room, hairdressers, sewing and knitting studios, and a small shop. Creating gardens, agricultural projects and ponds for fish farming provide food and produce to sell at the market.

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The achievements of the chil-dren’s project could be suc-cessfully built up on a uniform and broad basis. This means all the important areas of edu-cation, health, nutrition, water and energy supplies, agricul-ture, business activities and creating jobs should be devel-oped in parallel.

CONCLUSION

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The intention is that all these projects should be managed independently, thus helping the people to become self suffi-cient.

The main aim of this trip was to find out how the Remscheid support organization “Our Children and our Future e.V.” could best help local hospitals. The following are short ex-tracts from Franz Lebfromm’s diary. He was accompanied by the physician Dr. Helmut Cuntze.

TuesdayAfter breakfast we took Helmut to Villa Maria Hospital. Later he described how the hospital is very poorly equipped. The X-ray and sonication equipment belong in a museum. The sterilizer is not reli-able and urgently needs replacing. The head doctor is apparently the only medic there regularly. Ideally, young doctors could come here for at least three months – but the problem is specialization in Ger-many. All doctors here have to do everything: caesarians, appendix, childbirth, diabetes, malaria, AIDS. The patients in the hospital are cared for by their relatives. There is no hospital kitchen or laundry.

ThursdayAfter visiting the German Embassy, we went to Quality Chemicals Limited in Kampala to pick up the 60 impregnated mosquito nets (Dawa Plus 2.0®) donated to the project by Bayer Environmental Science. Afterwards we met Prossy. “Our Children and our Future” make it possible for her to study at the Makarere University in Kampala. After returning from Kamukongo the previous Monday she felt weak and feverish. It turned out she had malaria. She received the first new mosquito net.

MondayVisit to Villa Maria Hospital where Helmut was last week. Today we were allowed to take photographs and film. The hospital has no mosquito nets for the patients or staff because they are too expen-sive. Malaria patients are not isolated so many other patients catch malaria as well.

TuesdayVisit to the Kitovu hospital today. In terms of mosquito nets the situation is the same as at Villa Maria. Malaria patients are not in isolation and disease transmission is high. Nets are only available in the station where severely undernourished children are fed for three months while their mothers are advised and trained in nutrition. All patients who come to the hospital are treated, even when they cannot pay.

DIARY: TRIP TO UGANDA IN 2009

Hospitals poorly equipped

DESPERATELY NEEDED: Mariko Naumann and Eric Löffler from “Our Children and our Future e.V.” (front) hand over mosquito nets to Dr. Moses, the senior doctor at the Villa Maria Hospital (standing beside two nurses).

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The “Latin American Network for Research on the Biology and Control of Triatominae” (ECLAT) supports Chagas disease control programs throughout Latin America. It promotes basic and applied research on the biology and control of the disease vectors, Triatominae, and also acts as a coordinating focus between

scientists, operational personnel, and industries involved in Chagas disease control. Each region (Mexico and Central America; Andean Pact Region; Southern Cone countries) has a regional coordinator. Which vec-tor species are the main focus of research in each region depends on local populations and their adaptive mechanisms towards

ECLAT: Supporting Chagas disease control programs

More

http://eclat.fcien.edu.uy/

The “Trypanosomiasis Vector Research & Control Foun-dation” (TVRC) was set up to support control interventions directed specifically at reduc-ing and eliminating the social and economic problems caused by Chagas disease and African trypanosomiasis. Primarily, this focuses on eliminating the insect vectors

TVRC: Eliminating social problems caused by trypanosomiasis

of these diseases (domestic Triatominae and tsetse flies). It also involves supporting research into methods for controlling these two diseases, Chagas in Latin America and African trypanosomiasis, or sleeping sickness in Africa. TVRC seeks to raise funds from other sources, such as other foundations, interna-

becoming more domesticated. Network reference centers provide services for network participants, such as developing and application of specific tech-niques, quality control, and problem solving (see page 15).

tional organizations and industry, and directs these funds to dedicated research networks such as ECLAT and the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC), now part of the African Union (see page 23).

DEBILITATING DISEASES caused by trypanosomes are difficult to treat, lead to terrible long-term suffering and death.

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security troops there, fleeing in 1916 to Spanish territories in what is known today as Equatorial Guinea. He was interned in Madrid until the end of the war.

Germany lost its colony after the war, but Kleine remained devoted to sleeping sickness research at the Robert Koch Institute. Together with Oskar Dressel from Bayer, he helped develop the drug Suramin, better known under its trade name “Germanin”, which is still used today to treat trypanosomiasis. During this time he traveled throughout Rhodesia and Tanganyika from 1921 to 1923. In 1929 and 1930 he returned to Uganda and

Tanganyika for research purposes. He became president of the Robert Koch Institute in 1933.

During the 1930s Kleine repeatedly returned to Africa to carry out research, and after the Second World War he decided to return to Africa permanently. He died in Johannesburg in 1951.

Kleine published his memoirs in 1949 with the title “A German Tropical Doctor”, but like so many autobiographies this has now been forgotten. However, his name will always be insepa-rably associated with working out the development cycle of the pathogen causing sleeping sick-ness, and revealing the role of the tsetse fly (see page 23).

Author: Günther Nogge

nlike other parasite diseases in Africa such as malaria or

river blindness, African trypano-somiasis, or sleeping sickness was not a major problem until the beginning of the 1900s. Then, exploration and colonization spread the disease until it became an epidemic. In 1902 the first alarming reports about sleeping sickness came from the colonial depart-ment of the foreign office in Berlin. The epidemic had spread along the Congo River, the most important traffic route in central Africa, from west to east.

Robert Koch, director of the Institute for Infectious diseases of what is now the Max Planck Society, informed the German Govern-ment about the disease situation in the German protection area in East Africa. In March 1906 he gave an important speech before the Kaiser and Minister of War, subsequently receiving 185,000 Reichsmarks from the govern-ment to research this disease. Koch was appointed to make a research trip to German East Africa. Dr. Friedrich Karl Kleine, leader of the Infection Department

at the institute, accompanied Koch on this trip in 1907-1908.

Kleine, born in Stralsund, Germany, studied medicine in Halle and was then an army doc-tor before going to the Robert Koch Institute in 1900. From 1907 to 1914 he led the efforts to

combat sleeping sickness in German East Africa. During this time, he wrote two vital papers on the biology and transmission of trypanosome parasites, which were published in 1909.

In Daressalam he founded a microbiological institute that still exists today. In 1914 he took over research into sleeping sick-ness in the Cameroon. With the outbreak of the First World War, Kleine was enlisted into the

R E T R O S P E C T I V E

History: 100th anniversary of describing the tsetse fly as vector of sleeping sicknessThe first to reveal the role of tsetse flies in transmitting sleeping sickness was Friedrich Karl Kleine. The renowned expert on the tsetse fly, Günther Nogge, commemorates the centenary of this important discovery with a short biography of Kleine, who pub-lished two papers on the biology and transmission of trypano-some parasites in 1909.

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Friedrich Karl Kleine (second from left) together with Robert Koch (sitting) during the research trip to German

East Africa in 1906/07.

PUBLIC HEALTH JOURNAL: No. 21 on CD-ROM

We wish you a pleasant and informative read.

If the CD-ROM is missing, please contact your Bayer Environmental Science regional manager for a complimentary replacement (see green box on the right).




ECLAT (Latin American Network for Research on the Biology and Control of Triatominae)http://eclat.fcien.edu.uy/

Food and Agriculture Organization of the United Nationswww.fao.org (search: tsetse and chagas)

IAEA (International Atomic Energy Agency)www.iaea.org (search: tsetse)

Malaria Consortiumwww.malariaconsortium.org

Malteser Internationalwww.malteser-international.org

Oswaldo Cruz Foundationwww.fiocruz.br/

Our Children and our Future e.V.www.our-children-and-our-future.de

Pan American Health Organizationwww.paho.orgwww.paho.org/English/AD/DPC/CD/chagas.htm

PATTEC (Pan African Tsetse and Trypanosomiasis Eradication Campaign)www.africa-union.org/structure_of_the_commission/deppattec.htm

Stellenbosch Universitywww.sun.ac.za

Swiss Tropical Institutewww.sti.ch

University of Edinburghwww.ed.ac.uk

University of Greenwichwww.gre.ac.uk

WHO / WHOPESwww.who.int/whopes/

WHO (Neglected diseases)www.who.int/neglected_diseases/

Link ListWith reference to the topics in this issue of Public Health Journal we include a summary of the main Internet links, where you can find further information, the latest reports and statements.

Head of Global Vector ControlGerhard Hesseemail: [email protected]

Australia / PacificJustin McBeathemail: [email protected]

Eastern Mediterranean AreaBora Erbaturemail: [email protected]

India Anil Makkapatiemail: [email protected]

Latin AmericaClaudio Teixeiraemail: [email protected]

Southeast AsiaJason Nashemail: [email protected]

Sub-Saharan AfricaMark Edwardesemail: [email protected]

EventsFourth Asean Congress of Tropical Medicine and Parasitology June 2-4, 2010Singaporewww.ssmb.org.sg

XIIth International Congress of Parasitology (ICOPA)August 15-20, 2010 Melbourne, Australia www.icopaxii.org

American Society of Tropical Medicine and Hygiene (ASTMH), 59th Annual MeetingNovember 3-7, 2010 Atlanta, USAwww.astmh.org


FOR INFORMATION PLEASE CONTACT

You can find all links on the enclosed Public Health CD-ROM

PUBLIC HEALTH JOURNAL: No. 21 on CD-ROM

As a special service for readers of Public Health Journal we include a CD-ROM (see inside back cover). Not only does it contain every page of the complete issue in pdf format, but also the individual articles. Some feature additional information.

Imprint

Public Health Bayer Environmental Science Journal No. 21February 2010Publisher: Bayer SAS, Bayer Environmental Science 16 rue Jean-Marie Leclair CP 90106, F-69266 Lyon Cedex 09, FranceEditor-in-charge: Gerhard Hesse email: [email protected]

Editors: Michelle Cornu (Bayer Environmental Science), Michael Böckler (SMP Munich), Avril Arthur-Goettig Realization: SMP MunichLayout: Artwork (Munich)Printing: Mayr Miesbach GmbH (Germany)

Comments expressed in this Journal are the views of the authors, not necessarily those of the publisher. Copying of any text and graphics is only allowed with permission of the publisher and/or specific author(s) of the relevant article(s).


TSETSE INFESTATION The tsetse fly, genus Glossina (picture), infests immense tracts of potential farming land in Africa. People avoid living there for fear of contracting trypanosomiasis, known as sleeping sickness in people and nagana in livestock. The only way to eliminate the disease is effective, large-scale tsetse eradication and keeping the land tsetse-free. That this is feasible has been demonstrated in Zanzibar, Botswana and Namibia.

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