Malaria transmission and vector biology on Sainte Marie Island, Madagascar.

A 17-mo longitudinal malaria survey (November 1988-March 1990) was carried out on Sainte Marie Island, an area on the east coast of Madagascar which is frequently visited by tourists. During 706 man-nights of capture, 46,401 mosquitoes belonging to 32 species were caught. Sporozoite rates were determined by ELISA and incriminated Anopheles gambiae Giles s.s., An. funestus Giles, and An. mascarensis De Meillon as vectors of malaria. An. gambiae, the main vector, was highly anthropophilic but largely exophilic. Transmission by this species occurred mainly from November to April; the overall circumsporozoite antigen positivity rate was 1.7%, with a maximum of 3.2% in March-April. The nightly peak of transmission occurred between midnight and 0400 hours. The annual inoculation rate was calculated to be 100 infective bites per human, of which 92 were of Plasmodium falciparum. An. funestus played a minor role in transmission. An. mascarensis, an anopheline endemic to Madagascar, was incriminated for the first time, as a malaria vector. The sporozoite rate in this species varied from 0.4 to 0.9% as shown by both ELISA and salivary gland dissections. Parasite indices in humans up to 20 yr of age fluctuated during the year from 64 to 80%. Bed nets are recommended for malaria protection for the local population and tourists.