Status and future control

Status and Future of Control

ln spite of some recent advances in the field of i t s epidemiology and control, hu- nian and animal C3ot;sina-borne African trypmosvmidsis c a n t i n ues to present a formidable challenge to health and econ- wily in many countries of tropical Africa by crippling animal husbandry and caus- ing sleeping sickness. This fatal disease in man is periodically reported from many widely scattered areas, and has recently dppeared in an epidemic form in several countries of the continent. It is estimated that the threat of trypanosomiasis persists today over at least 10 million km2 of tropical Africa, including 7 milliqn km' that would he suitable for the grazing of livestock, should the disease be fully con- trolled (FAO 1974).

Of the six main Glossina-borne 7 j - pdflo5Oma species of socioeconomic importance occurring in Africa, four affect livetock and have wild animal reservoirs (T. brucei, T. congolense, T. simiae, and 'I. vivdx), one is a zoonosis with acute clin- ical forms in man and discrete infections i l \ cattle and game (T. rhodesiense), and the last is mostly, if not entirely, restricted to man (T. gambiense) (MacLetinran 1975). Drugs are available foc individual and IMSS treatments and can be used to pre-

vent infection. However, they h4ve un- pludsant, and soqwtimes dramdtic side effects. Furthermore, there is incrmsing evidence of the devclspment of strains of the parasite$ resistant to many of the compounds currently available, while nu new drug hds been developcd in recent yedrs by the chemical industry (Finelle 2975; MacLennan 1975). The development of immunizstion methods is under serious consideration but will probably require many years before reaching an operational stage. To totally eliminate the feral reservoirs, while simultaneovsly treating all the livestock with chemotherapeutics, constitutes neither a feasible nor even an acceptable proposal. At present, G1or;sma control thus constitutes the mcxt promising approach to the enduring elimination of the disease. Ideally, and un a long-term basis, vector eradication would represent a cheaper and much more realistic solution than control campaigns, which must be carried out year after year without any time constraints and despite the high re- current costs (MacLennan aiid Na'isa 1973).

Partly as a conseqqence of the cata- strophic drought that recently affected the African continent (Temple and Thomas 1973), and partly because of the long-felt need to rapidly increase agricultural production, the FAO (during the World Food Conference organized in Rome in Novem- ber 1974) suggested implementing a long- term program which, over a period of 40 years, would eradicate tsetse flies and bring trypanosomiasis under control over 7 million km2 of potentially suitable grazing land (FAO 1974). The Conference en- dorsed this proposal. Such a program, after an extensive preparatory phase devoted to applied research, training, geographical reconnaissdnce, and socioeconomic studies, would involve the eradication o# tsetse Aies from about 200 O00 kmllyear a! an anticipated average annual cost of USSS6 million, with the un- derstanding that about 40% of the area might require treatments durlng several Succegsive years to cape with both rein-

,

I i

*'

36 IDKC-077e

vasion by tsetse flies, and foreseeable operational weaknesses. Funding and implementation of the preparatory period is underway. The operational phase, which should begin around 1980, could În many ways follow the example of the policy ear- lier adopted in South Africa (du Toit et al. 1954) and in Nigeria more recently (Mac- Lennan 1968; MacLennan and Na'isa 1973); but with the addition of all later technical, methodological, and operational improvements required by an endeavour of such magnitude.

Glossina Control Today

Since Glossina was first suspected of transmitting trypanosomiasis, many approaches were followed either to control tsetse or to prevent them from transmitting the disease. However, of these, the mass-release of parasites never gave good results, trapping had a very limited appli- cability except in a few special instances, bush-clearing and game extermination (quite apart from the fact that they are environmentally objectionable) usually had an unfavourable cost-effectiveness ratio, whereas genetic control methods were not found promising ori a large scale. Therefore, for many years, insecticides constituted the only alternative. Their application, based on a sound knowledge of the target tsetse species' resting places and feeding habits, and on the use of suitable equipment, has become cheaper with time (Finelle 1974; MacLennan 1968).

Dieldrin and DDT, and in some instances HCH, were the only insecticides used on a lar'ge scale and for extended periods, the first two mostly a4 residllal' sprays, the last mainly for fogging. Al- though the first large-scale tsetse eradrca- tion campaign had been carried out in South Africa with aircraft and many studies had been made o f the aerial application of insecticides for Glossina cantrol, almost all the importanti control campaigns 111 the past were carried out with residual iyecti-

4 1

cides applied from the ground - either with hand operated sprayers or with vehi- cle-carried sprayers and mistblowers. If the residual effect lasts longer than the G~ussind puparial period, ope application can: (1) theoretically eradicate the vector from the treated area; and (2) usually achieve tsetse eradication. Full particulars on the methodologies used can be Found in many recent reviews on the subject (At- kinson 1971; Raldry 1963, 1964b; Rurriett 1970; Davies 1971; Ford 1971; Jordan 1974b; LeRoux 1974; Lycklama dnd Nije- holt 1968a, b; Riordan 1966; 'Tour6 et al. 1975).

O n a long-term basis, however, the situation is not so simple. Because of the logis- tic difficulties involved, the ground application of insecticides to the vegetation of sparsely populated, and/or uninhabited areas is a time-consuming operation requiring much manpower and very rhor- ough supervision (LeRoux 1974). As tsetse flies can fly relatively fast and far, move with game and cattle, and be dispersed over long distances by vehicles, reinvasion of the treated areas constitutes a perma- nent threat (Davies 1975). The costs of maintaining an effective barrier zone are often very high. In one of the best organized tsetse eradication programs, the elimination of the fly is being carried out at the rate of about '12500 km2/year, in the dry or moderately humid savannah zone of West Africa. This, ín dddition to the over- all geographical reconnaissance, planning supervision, and evaluation activities, requires a small army o f about 2000 people and 60 vehicles (Na'isa 1974). As well, about 10% of the area requires a second treatment for various reasons. Some parts must be treated, ve thrge 'br more times before eradicatio t h a +t hieved. In more humid zones difficulties are greater because: ( I ) the vegetation cove1 is denser and rep- resents a greater proportion of the totd area (Davits 1975); and (2 ) there are usually two wet çeasons a year - with the result that only d brief period at the begin- ning of the longer dry season is fully ClWnvenieht fbr thr! applkation of residual

e l

I l

IC grourd - either trdyers or with vehi- iiid rnistlhwers. I f 51s lunger I h m L 1 1 ~

iod, one ,ipplicalion t ~ r d i c a t v the vector 'a; ancl ( 2 ) usually ilun. Full pclrticulars used ~ ' ~ i i be found

-I on the subject (At- 903, 1964b; Burnett I..ord 1971 ; lordan l.ycklama m d Nije- 1 1966; Tour6 et di.

fi, however, the situ- I3eccluse of the logis- i , the ground appli- to the vegrtation of lnd/or uninhabited mrng operation re- "ver and very thor-

fast and fu, inove , and be dispersed vehicles, reinvasion unstitutes a perma- 975). The costs of ve barrier zone are 2 of the best organ- programs, the elimi- 'I: carried out at the mz/year, in the dry savannah zone of

ildition to the over- naissance, planning intion activities, re- about 2000 people

sa 1974). As well, I requires a second edsons. Sonie parts hree or inore times hieved. In more hu- Ire greater because:

'r i5 denser and rep- 1)ortion of the total Id (2) there are usu- year - with the re-

perjod at the begin- dry Season is hlly qAication of residual

I)UX 1974), AS tsetse

The filling of hck-pdck sprayers for selective reskhial application$ of Chari River Vdlky , Chdd, (I A4ay 1973, M. Laird).

Kdldmdlollrf &:?ier VLJ,

treatments. 'Therefore, late applicdtlims could result in the insecticide deposits being washed away by the rains before the last tsetse emerge from their underground puparia. Furthermore, the growth of the vegetation is faster than in the drier zones, and a large proportion of untreated resting places is rapidly provided within a few weeks of the application.

The need to cover large areas Juring the most appropriate period of the year re- awakened interest in the aerial application of insecticides. Two diffçrent lines of approach were considered; (1) several @e-

quential dpplications of noripersistent insecticide deposits; and (2) a single application Qf a residual deposit.

Risks resulting fram environmental con- tamination have always been kept in mind when planning and implementing large- scale pesticide applications for tsetse fly control [Graham 1964; Koenlan and Had- den 196a; Langridge and Mugutu 1968); whereas obvious eçanomic considerations have led to the use of the lowest effective dosages. Huwever, the rqlative importance of environmental consideratione has stead- ily increased to the p where they could

prevent the production of the residual insecticides presently employed For Glossina control (Djerassi et al. 1974; Jukrrs 1974), or interfere with the funding of large-scale and long-term programs based on their use. This has induced both a more thor- ough assessment of the impact of the tsetse control treatments on nontarget organisms (Koeman et al. 1971, 19741, and an acceleration of the search for economically and environmentally acceptable alterna. tive insecticides and nunchemical control methods. The most promising alternative to date is based on the mass release of sterile males (Itard 1975a), whereas the use of parasites, pathogens, and predators is also under study (Cruvel 1974b).

The Search for and Evaluation of Insecticides

The first systematic investigations carried out for screening new insecticides thal could be used for Glossina control began about 15 years ago. Thesfa investigations were oriented toward the development of compounds and formulations thdt could be applied from aircraft (Burnett 196 I , ‘1963). Some af the more promising compounds were subsequently used, either for experimental purposes (Burnett 1962; Bur- nett and Thompson 1956; Burnett et al. 1961,1964; Foster et ai. 1961; Hocking and Yeo 1953; Hocking et al. 1953a, b, 1954a, b, c, 1966; Irving and Beesley 1969; Irving et al. 1968; Lee 1969; Tarimo 1971a; Tarimo et al. 1970, 1971a, b, 1972; Thompson 1953) or for tsetse control operations. One o f them, endosulfan, is now widely used in East Africa (Anonymous 1973; Kendrick and Alsop 1974; Park et al. 1972; Robert- son 1971).

After several years of interruption, these investigations were resumed as part of the global W H O Programme for Evaluatírig and Testing New Insecticides (WtK’) 1971, 1974). Roth the residual contact activity and intrinsic toxicity of the candidate

Iection of new inswticidet; for tsetse control that were to be tried as iwiidual drpos- its a5 well as ultra-low-volume (ULV) applications (Hadaway 1972; kladawdy and Turner 1915; Riordan 1971). Some of the most promising compounds hdve been ex- pcrimentaliy used under operational conditions, but from a cost-effectiveness viewpoint, the results obtained to ddte havr not been very encouraging (Challier and 1.0- rand 1972; Chdl1ic.r et n l . 1074; Spwlbcrger and Na’isa 1975; Tarimo et d. 1973).

lnvestigations are also under way to as- sess the poteqtidl of the new chemic.aIs tu accumuldte through food chains and to persist in the environment. Some systematic sludieti have been undertaken to de- termine the impact of dieldrin upon non. target organisms, when i t is applied to riverine vegetation as a residual deposit against tsetse, either from the ground or from the dir (Koemdn ct al. 1971, 1974; l‘oure et al. 1975).

The Aerial A plication of

Control Insecticides P or Glossina

Low- and Ultra-Low-Volume Applications

The aerial application of insi.ctic:idcs at low- and ultra-low-volume, and tIirrefor(1 dosage, for Glossina control does not pro- duce persistent deposits on the vcgctation of the treated area (Lofgren 1970). The purpose of this treatment is therefore re-

“strictrd to the complete ur almost corn- plete destructioi~ uf the population of adult flics existing within the zone uncier attack at the time of treatment. ‘1’0 msure lasting results, sequential dpplications must be carried w t $1) that the young fe- niale flies that have emerged from pipairia since the previous treatment a r c killed he- fore dcpositing their first larva. I’opulation dynamics and simulation studicis have indicated that i t could lie I t w exp(>nsivp IO

aim, not for tht: corni)lrte dimination of chemicals were usrd as d basis for the se-. tscalsc flies on the wing duyirlg dtiy given

plication of ir Glossina rol

, dume Applications

11 uf insecticides at tine, and therefore ritrol does not pro- l on the vt:getcjtion 1JFgrt.n 1970). The r r t i 5 thert+ore re-

or almust CWTI-

.he pvpul.itic,n c ) f

. in the zone urrdcr ~kt ln~nt . 2-c) eilhure ritial ayp l i c~ t~uns khat the young fc- qged f rom pLl[Jdt¡d I l r r r i t are klllrd be- ,t iarvd. I'opulativn ln studies have in-

less expensive to tete elimination of

during any given

i

I

i

i

e

L. t

treatment, but rather, for dn increase in the number of treatments; on the assump- tion that below a certain density, isolated flies do not find mates and die without producing progeny. Unfortunately, tsetse have an incredible ability to survive and to reproduce Lj t cxtrtmely low densities, as observed during many eradication programs. I t is thus safer to use an effective dosage, and to carry out a number of dp- plicdtiorls allowing for a reasonable mar- gin of safety. III lhe highlands of East Afri- ca, the most coinmonly used schedule involves five applications 3 weeks apart.

To be fully effective, ULV appliations must be made in such a way that almost AI! the droplets hdve a11 insecticide content sufficient to kill a single tsetse, while lack- ing d n ex ces^ of toxicant. This implies that d narrow droplet-size spectrum should be used.

I t is ~ l s o very important that the number

of droplets per unit of s~irface ~ r c d ur vol- u i w ensures a fair chsnce that (Bach tsetse i5 hit by at least one droplet. This means thdt the droplets should be both numer- ous, and small enough lo float in the air fur long enough to drift over an area much larger ttidii the aircraft wiiigspin before settling on the ground or oil vegetation or being lost (through evdporatinn, by Grift- ing away from the target x e d , etc.). These conditions can only be mel by a few insecticides that: (1 ) have J high intrinsic toxicity for tsetse; (2) are liquid in their technical form at room temperature; and (3) cai1 be forrnulatcd as liquids without excessive dilution. Experience has established that the moet appropriate droplet size is about 20-30 pm (VMD). in view of the above, this demands compounds having d me- dium lethal dose for a tsetse fly of about 1-12 ng/fly. Among the insecticides ful- filling thesr! conditiontj are some synthetic

. c

$1 o

I

pyrethroids, fenthion, some newer or- ganophosphorus compounds, dieldrin and endosulfan (Hadaway and Turner 1975). Endosulfan is extensively used for the purpose because it is relatively cheap and does not persist in the environment. However, i t is acutely toxic to fish.

The fate OF small droplets applied from a low-flying Aircraft depends to a large extent upon air currents, as significant up- ward air inovemrnt will dispersc tt1c.m through the atmosphere. ‘I’hercfore, in practice, only a few hours per day (wually in the rnrly morning and late evening) a i e convenient for such applications. Night

operations are carried out (Kendt-ick and AIsop lY74; Iee et al. 1975), but they rdise other serious operational problems. It could be more difficult to hit resting Ries at night than active flies thdt arc very often on the wing,

Nonresidual aerial applicdlions are riinde using eithttr a thermal fogging de- vice (Hocking and Yeo 1953; I’ark et al. 1072), in which an insecticide formulation is injected into ttie exhu,st pipt. o f the aircraft, Qr with soiiie hmn of rotary atomizer (Irviny: aiid Heedey I%*; Irving t*t al. ’1968; Kendrick and Aisop 1074).

U ~irig cvid osi^ Ifm, the first 1.3 rge-scale

Y

2

out (Keidrich arid '751, but they raise

problems. I t o hit resting fires a t

I hpt arc' very often

dppliCdtlo115 dre

ermal fogging de- J 1953; Park et al. trcide formuidtion list pipe uf the air-

* of rotary atomizer f . Irving el al. 1968; 4,). ie first large-scale

LAIRD: TSETSE h l ,

ULV applications were carried out with a very large s'rfety factor. Dosages of about 30 g/ha for e x h applicdtion were employed, With itnproveinents in equipment design (Lec et al. 1969) and insecticide formulation, Ckssina, control campaigns have recently been carried out with dosages as low as 6 g/ha (Kendrick and Alsop 1974; Lee et al. 1975). The use of pyrethrum (IN- ing et al. 1968; Tarima et al. 1970,1971a, b, 1972) has given inconsistent results. More

'!, recently, a synthetic pyrethroid was used on an experimental basis (Lee et al. 1975), but the dosage was too low (0.6-12 g/ha) and the results were inconclusive.

' Aerial ULV applications of insecticides have been rather successful in the wooded savannah areas of East Africa (Anonymous 1973; Kendrick and Alsop 1974; Park et al. 1972; Robertson 1971), and could probably be adjusted for increased flexibility and effectiveness (Bals 1973; Barlow and Hada- way 1974; Maas 1971; Niessen 1974; Tar- imo 1971b). It would be desirable to assees the value and limitations of the method in the savannah zones of West Africa, especially in areas where the wooded savannah i5 intermingled with gallery forests that constitute the main resting sites of the tsetse flies during most of the dry season. I t was recently shown that only a small proportion of the insecticide applied over such a gallery forest reaches ground level where the tsetse are both active and a t rest during daylight hours (Johnstone et al. 1974).

High Volume Applications

The aerial application of insecticide at high volume, and usually high dosage, en- ables a long-lasting residue to be deposited upon the vegetation. Under ideal conditions, a single application is sufficient to eliminate tsetse from the treated area. The purpose of the treatment is thus the same as that of residual applications made from the ground. The inherent advantages of aerial application are that: (1) it does not require an elaborate infrastructure and a large number of staff and vehicles; and (2)

large areas c m be treated in a relatively short period of time. One obvious diaad- vantage is that mgst of the insecticide droplets settle on tbc ~ p p ~ Ieiwefi and branches (sites nut canslergd as favoured resting places for the fly),

This technique was used experimentally - with a great degree QI SUCCWE - asaiMt G. pallidipes Inhabiting dense thickets in the b m b w e Valley, Kenya; dieldrin being applied as an invert emulsion requiring special application equipment. After the initial demonstrratiqn of the feasibility of such an approach, the trial3 were aban- doned (Allsop and Baldry 1972; Baldry 1971; LeRoux and Platt 1968). Some investigations were also undertaken in East Af- rica using aircrdft applications of defoli- ants at a high dQsage as a preparation for the subsequent application of insecticides (Tarimo et al. 1974).

In West Africa, helicopter application of insecticides dt high volume has been used, both routinely and for experimental purposes (Bauer 1971), against both riverine tsetse flies and G. m. sub~norsitans (which at the height of the dry season behaves almost like a riverine species). Outstanding succe~ises were achieved in Niger and Ni- geria with dieldrin (lOOO-aoOa g/ha), endosulfan (1500 g/ha) and a mixture of DDT, HCH, and dieldrin (respectively 1150,450, and 450 g/ha) (Spielberger 1971; Spielberger and Abdurrahim 19'71, 1975; Spielberger and Na'isa 1975; Spielberger and von Sivers 1970; Spielberger et al. 1971). Less satisfactory results were obtained with other insecticides that had been tentatively selected in view of their greater environmental safety. In the case of the investigations carried out in Mali, this lack of SUCC~SS might have been due to operational and equipment problems (Challier et al. 1974; Spielberger and Na'isa 1975).

At high volume, pnd especially when the target is not qn open OF flatwowled savannah but a gallery forest and fb i diate surroundings, the q" of tensive insecticide drift conetitu@ Qbvioqs disadvantage. This tS

47. IORt ' 077e

using larger droplets of about 65-150 pm (VMD). As already indicated, droplets of that size settje mainly in the upper canopy and only 1-1.5% of the insecticide reaches ground level within the gallery forest (johnstone et al. 1974). Nevertheless, field trials have shown that this can be suHiCient to kill tsetse, perhaps because, at certain periods of the day, Glossina rest on the ground vegetation, close to, but out- side of, the gallery forest. It is also strongly suspected that a t night the gallery forest canopy constitutes an important tsetse resting site (MacLennan and Na'isa 1973). These aspects of the riverine and riverine- like Glossina have so far been inade- quately investigated (Glover 1967). Further studies might allow a more judicious use of insecticide. Investigations are in progress on the insecticide formulations used for such purposes. Their results inay lead to a reduction in the dosage of active in-

gredient by the formation uf insecticide deposits combining longer persistence with better availability to the tsetse ( i h r - low and Hadaway 1974; Niesserr 1974).

'The immediate impact of these high- volume dieldrin applications on nontarget organisrns in the gallery forests can be cira- matic (Koeman et al. 1974), but the long- term effects haw not yet been assessed. As long as the actual treatments involve a small fraction o f a small arca (for example, the gallery forest and its immediatc surroundings), there is J likelihood of repopu- lation of the treated zonr by birds, mam- mals, and insects from the immediate vicinity of the trcated zone (Ldligridge and Mugutu 1968). 'I'he situation could be less favourablr~ i f. the tren t me n ts c.ovoi.ed tens of thoyiands of square kilometres over a short period of [inle. I t must be further n o t t d t ha t duri!ig the dry srason, such gnl- lery Furwts usu~~l ly sheltcr nrost of thr

a

.ition of insecticide longer persistence to the tsetse (Bar:

:; Niessen 1974). 1,lct of these high- .itions on nontarget 4 forest5 can be dra- 1974), but the long-’ ct been assc~wd. AS i * ,~ t~nen t s involve a I I drcd (for example, its immediate b u r -

lcelihood of repopu- me by birds, mani- )m the immediate .:one (Langridge and uativn could be less irients: covered tens (! kilometres over a It must be further

iry season, such gal- iielter most of the

wildlife and other nontarget orgat~isms o f the SdVdnndh zones ot West Africa. ‘Ihe elimimtion of the species resting there during that period could be as Lornplete and durdblc as that of tsetse flies. Such ‘I

risk must, therefore, be most thoughtfully assessed before the authorization of high- volume applications from aircraft over very large areas (FAO 1974),

’: insecticide Applications and Integrated Control Approaches

Although the use of pheromones and other attractants associated with traps cannot be discounted, it seems most probable that in the near future integrated Glossina control methods will often be based on the combination of insecticide applications and the release of sterile male flies (Itard 1975.3). In the more distant future, parasites, predators, and pathogens might also be used to complement the action of insecticides (Gruvel 1975a).

Residual applications of insecticides, whether from the ground or from the air, would interfere for a‘ lengthy period with the inundative release of sterile males, predators, and parasitoids, but not with the use of pathogens. The interval between the last insecticide application and the be- ginning of the sterile-male fly (or predators, or parasites) release, should therefore be adjusted to the effective residual life of the insecticide deposit, as well as to the population dynamics of the tsetse species under attack. Under the most favourable conditions the releases could probably be safely made the year following the application of residual deposits. Under less favourable conditions, it would be unsafe to wait more than a few months (Anonymous 1972).

Sequential ULV applications of insecticides, made from the air or even from the ground (Challier et al. 1964; Kemaghan 1954; Tarimo 19741, have little residual effect and therefore constitute the best ap-

proach when preparing for the subsequent use of any biological or genctiç control mcthod.

i t might appear simpler to cdrry out ad- ditional ULV applications or another round of rcsidud spraying - or to tn- crease the dosage of the insecticide used - than to .tollow up the insecticide treatments by using nonchemical control methods. However, it i s always the last couple of tsetse flies that are the most costly to kill, while the application of chemicals dlways interferes 10 some extent with the equilibrium of the treated ecosys- tems. From a purely theoretical cost-effectiveness viewpoint, integrated control medsures may therefore be as efficient as, and cheaper than, chemic4 control methods used alone (WHO 1975). One of the potential advantages of integrated control measures is that sterile males, parasites, predators, and pathogens may reach small residual Clossind populations survivu~g insecticide applications because they were living in unsuspected microniches that were not treated. These individuals, just because they are atypical, cannot be easily eliminated by increasing the insecticide dosage and/or number of applications (Toure et al. 1975). These hypotheses have yet to be tested through actual operations.

In a number of instances, Glossina eradication, even if constituting the long-term objective, may not be economically feasible or justified by socioeconomic studies; whereas, a considerable reduction of tsetse fly abundance is required Lo curb sleeping sickness epidemics, to settle people, or to establish trypdnosomiasis-tolerant cattle (Ford 1969). Under such conditions the sequential use of insecticides and nonchemical agents might constitute b suitable long- t e rn solution. For these purposes the release of other biological agents would be preferable l o the release of sterile males, because the vectorial capdcity of male tsetse is not impaired by sterilization, uni less their Lifespan is considerably short- ened. -1. Waman, R,A.T. Baldry, J.D. Parr ker, A. Challier, and A.R. Stiles.

I

I I )I<C-O77r lM7

BibÏ iography

(Abbrevistion!,: CCXA - Ci)mmittee for Kx/vìic,j/ Cooperatien in Atrlcd Svuth of thc *%hard, COI'R - Ceii tre for C3vtweds Peest Kesedrch, EATKO - East African Trypdnnrr~miaris Hwarrh Qrguisdlion, IIAO - Food dnd Agriculture Clrganization of the United Nations, IAEA .--.I

Intercidkiondl Aloniic Energy Agency, IEMVT - Institut d'devdge et de mdddedne v&tPriiìdjre des pdys tropicdux, ISCTT(C - 111 ternational Scientitk C..opncd for 'rrypanosomi&7is Rescrarc-h and Gantrd (of OAU), NAS - National Academy of Sciences, (Of USA), NJTß - Nigerian Inlitute for Tr)tprrnosornidsis Resexch, (3AU - Orgdnirdtion for African Unity, occGE -- i%gdflhthn de coordin'itiuii et de coopération pour la lutte con trç' les grandes eed&nies, QRSTQM - Ofice de la recherche scicntifiyue et technique Outre-Mer, 5rRC -, Scientific, Twhnicpl and Resetlrch Commission (of OAU), 'TPRI - Tropicill Pesticides Research fnqtjtutg, WHQ - World ,He& I

Allsop, R., and Ualdry, L).A.'T. 1972. A geiler.ì/ descriptio11 o f the Lambwe valley Ared of south N ~ J I I Z J District, Kenya. Bull. WHO, 47,691-697. , . --. ,

Anonymous. . .__.- 1972. Annudl Report 1971. Republic o f

Kenya, Department of Veterinary Services, Govt. Printer, Nairohi, p. 31. 1973. Annual Rrport 1972. Republic of

Botswana, Department of Animal Health, Gaborone, Botswana, p. 3. - .

Atkinson, ¡>.I<. 1971. A comparison o f 1)DT w.p. .ind dieldrin ex. for tsetse fly control in Botswana. t'est Articles and News Summar-

-. -

Hurnstt, G.F. 1961, 1963. ?'he s u s r t y f i h b l v 01

insect~c~des. U d 1 Ent. Krs, 52, 531-539, belSe flic5 tU tOplCJl d p ~ 7 ~ l C 4 t l C ~ I I 5 Of

963-968; 53, 337-345, 387-354, 747-752, 753-761. 1962. Resedríh in 6 s t A f d a on the con-

trol of tsetse die5 froin the $ir. Agrio. AVICI- tion, 4,7947. I

1970 Cbritrol by insecbcides. Geiiridl con- sider.itron5. Kes(du.d deposits, d t v d d m ì ground dppIi í&on, pyrt*thrirm derosi)lr. In Mulhgdn, H. W., 'l'hc African trypdriosonuds- es, Allen & Llnwin Ltd., London, 464-520

Uuinett, L F , Chadwiik, P k , Miller, A.W.I)+, arid Beebley, J.S.S. 1964. Aircraff dpplicdtiori5 of insechrides I I I E ~ 5 t Africa. ,YlV. b'ery low volume aerosol!- tri drelclrrrl ,ìrid 15obt*rimn for the control of Glossirid morel.ms Westw. Bull. tnt. Res. 55,527-539.

Burnett, G.F., and Thompson, U.W. 1956. Aircraft apphcdflon of in5echcidt:s in tkst Af- rica. X An invtr5f1&1tron of the behaviour of coarse aerosol clouds in woodland. Bull. Ent. Res. 47,495-524.

Burnett, G.F., Yro, U., Miller, A.W.C)., and

secticides in East Africd. XIII. An economic method for the control o f GIo5siitd morshns Westw. Bull. Ent. Res. 52,305-316.

White, 1.1'. 1961. Aircrdft dppllCJt1kVlS of In-

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I DRC 07 7e

'* ?I 'Atd8 i: The future for biological methods in integrated control

Laird,M. cck- IDRC-OVe

iZii.' Tsetse: the future for biological methods in integrated cootrol, Ottawa, IDRC, 1977. 220p. .. I

btatus and Future of Controg 35- 4'3 ( ~ i ~ Y r r ~ ~ & ~ a y h ~ ~ bt47-W Glossina control today 36 The search for and evaluation of insecticides The aerial application of insecticides far Glossind control 38 Insecticide dpplications arid integrated control approaches

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K. Stilc's

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@ 1977 International Development Research Centre Postal Address: Box 8500, Ottawa, Canada KlG 3H9 Wead Office: 60 Queen Street, Ottawa

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Status and future control