USE OF POLYMERASE-CHAIN-REACTION TO IDENTIFY ANOPHELES-GAMBIAE GILES (DIPT., CULICIDAE) SIBLING SPECIES COMPOSITION

In an entomological study conducted in two high altitude malaria endem ic sites in Kakamega district, western Kenya (1995-96), Anopheles gamb iae sensu late (A. gambiae s.l.) and Anopheles funestus were the only two anopheline species collected and identified based on morphological criteria. Anopheles gambiae s.l. was the predominant species forming 83% (n = 2667) of the total female anopheline mosquitoes collected ind oors. In both ecogeographical sites, the two species showed different seasonal patterns in population densities and Plasmodium falciparum in fectivity rates both which are responsible for variation in malaria tr ansmission in the two sites. To establish the sibling species composit ion of the A. gambiae Giles complex 30% of the total A. gambiae collec ted were analysed by the DNA-based polymerase chain reaction (PCR). Al l 802 mosquito specimens tested belonged to one sibling species, A. ga mbiae sensu stricto (A. gambiae s.s). No A. arabiensis was present fro m the specimens tested. The results suggest that A. gambiae s.s. may b e the only member of the gambiae complex represented in the high altit ude sites in western Kenya. This species, unlike A. arabiensis, is hig hly anthropophagic and endophilic, and these behavioural trends may be useful in targeting specific control measures for this species in the high altitude sites such as indoor residual spraying and destruction of breeding sites. The present study is the first logitudinal entomolo gical study to be carried out in highlands of western Kenya where mala ria epidemics are frequent.