Nevertheless the reduction of the number of malaria deaths is one of the main reasons for the dramatic increase of the world population

since the end of WWII.

Mosquitoes: basic biology

• Larvae and pupae always found in water.

• Adult mosquitoes of both sexes feed on nectar.

• Females of most species need a blood meal for egg development.

• In temperate climate: diapause (adults in dormant state) or produce dormant eggs.

Mosquitoes: basic biology II

• Three major breeding groups:

– Permanent water breeders: Anopheles and many Culex in swamps, ponds, lakes, and ditches.

– Floodwater breeders: salt marsh, inland flood water, and rice field mosquitoes.

– Artificial container/tree hole breeders: Aedes aegypti and Aedes albopictus.

Mosquitoes as vectors

• Aedes: filaria, viruses (e.g. Aedes aegypti for dengue and yellow fever).

• Anopheles: malaria, filaria (Wuchereria bancrofti) , viruses.

• Culex: filaria, viruses (e.g. Culex pipiens for SLE).

Aedes aegypti• Worldwide within the

20°C isotherms.

• Vector of yellow fever

and dengue.

• Urban mosquito.

• Daytime biting mosquito.

Goddard J. 2003. CRC Press

Aedes albopictus

• Asian Tiger Mosquito.• Agressive, daytime

biting mosquito.• Associated with used

automobile tires.• Vector of yellow

fever, dengue and Lacrosse encephalitis virus.

Goddard J. 2003. CRC Press

Aedes albopictus

• Asian Tiger Mosquito.• Agressive, daytime

biting mosquito.• Associated with used

automobile tires.

Goddard J. 2003. CRC Press

Aedes albopictus

• Asian Tiger Mosquito.• Agressive, daytime

biting mosquito.• Chikungunya outbreak

in Réunion, a French “overseas département”.

• Arboviral disease.• Fever and arthralgias.

Eurosurveillance. 2006. Volume 11. Issue 1, at http://www.eurosurveillance.org/

Aedes albopictus

• Chikungunya fever in the province of Ravenna, Italy: A. albopictus is the most likely vector …

• A. albopictus in … Belgium, the Netherlands, …

Eurosurveillance. 2007. Volume 12. Issue 9, at http://www.eurosurveillance.org/

• A. albopictus in NL: via “lucky bamboo” from SE-China.

Ned Tijdschr Geneeskd. 2007. 151:1333-1338.

Anopheles labranchiae atroparvus

• Ziet gij muggen lang van poot? Aarzelt niet, maar slaat ze dood.

• Main malaria vector in the Low Countries.

• Lived in pig stables (Vapona strip) and attics (Sprays).

• The larvae are found in brackish water along the coast from the southern Baltic to Spain.

Anopheles gambiae

• Most important vector in Africa.

• < 1000 m• 2 (7) km• 0 – 4 h maximal

activity.• Endophilic species.

Anopheles gambiae

• 1930: Brazil.• 1937-1938: large fatal

epidemics associated with A. gambiae in Brazil.

• 1939-1941: eradicated from Brazil.

• 1943-1945: eradicated from Egypt.

The Lancet Infectious Diseases. 2002. 2:618-627.

UK NEQAS Parasitology on the web

Approximately 60 different species of Anopheles mosquitoes can transmit

malaria.

Malaria transmission

Mosquito to man

Blood transfusion

Mother to child

American Civil War (1861-1865): patients with mosquito nets, Washington D.C.

50% of the white soldiers got malaria annually

Alphonse Laveran(1845-1922)

• Physician of the French

Army.

• 1880: Constantine,

Algeria, The malaria

parasite: Laveriana,

Plasmodium.

• Nobel Prize in 1907.

Sir Ronald Ross (1857-1932) 20 August 1897: mosquito day

• Surgeon-Major in the British Indian Medical Service wrote to his wife: “I know that this little thing a million men will save”.

• Studied bird malaria.• Nobel Prize in 1902.

Battista Grassi

• 1899• Only female

mosquitoes are able to transmit malaria.

• Blood is necessary for oogenesis.

                            

                     

Courtesy CDC

Plasmodium falciparum limited to (sub-) tropical areas (summer isotherm of 20°C, altitude < 2000 m).

Sporogony in the mosquito

• Plasmodium falciparum– 8 days at 30°C– between 20 (18) and 33°C

• Plasmodium vivax– development occurs at 16°C

M. Wéry, 1995.

Developmental period in mosquito

• Plasmodium falciparum: 22 days at 20°C, 10 days at 27°C (minimal temperature (18) 2O°C)

• Plasmodium malariae: 30-35 days at 20°C, 25 days at 24°C (minimal temperature 16°C)

Beaver et al. 1984.

Developmental period in mosquito

• Plasmodium ovale: 16 days at 25°C, 14 days at 27°C (minimal temperature (18) 2O°C)

• Plasmodium vivax: 30+ days at 16°C, 16 days at 20°C, 10 days at 30°C (minimal temperature 16°C)

Beaver et al. 1984.

Malaria: Vector Control

• Source reduction (larval control)– Historically most effective campaign in Brazil

and Egypt (1930s and 1940s).– Bacillus thurigiensis var. israelensis (Bti

toxins).– Mosquito fish (Gambusia affinis): larger bodies

of water.

CDC, www.cdc.gov/malaria/

New strategy against Aedes aegypti in Vietnam

Kay B., Nam V. 2005. Lancet: 365:613-617.

• Major sources of A. aegypti are large water storage containers.

• 1998-2003: Elimination from 32 of 37 communes with Mesocyclops spp. (cyclopoid copepods) (309730 people).

• No dengue cases since 2002.

New strategy against Aedes aegypti in Vietnam

Kay B., Nam V. 2005. Lancet: 365:613-617.

• Mesocyclops spp. (cyclopoid copepods)

• WHO: only in countries free of Guinea worm (Mesocyclops spp. are intermediate host)

• Gnathostoma and Diphyllobothrium ?

Malaria: Vector Control

• Indoor residual spraying– DDT, dieldrin– more expensive insecticides– failure of eradication (1955-1969)– environmental concerns

• Insecticide-treated bed nets– pyrethroid insecticides– nets retreated at 6-12 months

CDC, www.cdc.gov/malaria/

DDT

• Dichloro-diphenyl-trichloroethane.

• 1874: German chemist: Othmer Zeidler.

• 1939: Paul Hermann Müller (1899-1965) in Switzerland (J.R. Geigy A.G., Basle).

• WWII: louse-borne typhus, malaria.

• 1948: Nobel Prize Medicine.

Parasitology orphan parasites orphan drugs

The disaster of the ban of DDT. The Lancet. 2000. 356: 265 and 1189.

2001: indoor residual spraying with DDT resumed in S. Africa and malaria cases fell. The Lancet. 2007. 369:1922.

(orphan reimbursement, B)

DDT indoor residual spray, …

• Still an effective tool to control Anopheles fluviatilis – transmitted Plasmodium falciparum in India.

Gunasekaran K. et al. 2005. Trop Med Int Health, 10:160-168.

Eradication of malaria

1934: Hans Andersag at Bayer discovers chloroquine1939: Paul Müller at Geigy discovers DDT1951: Sardinia malaria free1955: WHA (WHAssembly): goal of global eradication1955-1969: WHO uses DDT and chloroquine50’s: DDT-resistance1962-1970: chloroquine-R1955-1965: expenditure of $ 1.4 billion1969: WHO back to malaria control1975: Europe free of malaria for first time in history

Courtesy of C.D.C

Recent history of the World Bank's work on malaria

The World Bank co-founded the Roll Back Malaria (RBM) Partnership in1998. Since July 2000, the Bank has committed about US$100-150 million

in funds earmarked for malaria control. This includes only health sectorinvestment credits and grants, as well as commitments through broad programmatic operations such as Sector-Wide Approaches (SWAps).

Total World Bank support for malaria control was higher, due to financing through debt relief, multisectoral operations such as Poverty Reduction

Support Credits (PRSCs), Emergency Recovery Credits and Social Funds. However, it is difficult to quantify exactly how much of these programmatic

operations went to malaria control, since such operations do not track details of inputs into specific disease control programs.

RBM is enabling countries to take effective, sustainable action

against malaria by focusing on

1. preventing and controlling malaria during pregancy

2. promoting the use of insecticide-treated mosquito nets as a means of prevention

3. dealing effectively with malaria in emergency and epidemic situations.

4. providing prompt access to effective treatment