Malaria prevalence and a brief entomological survey in a village surrounded by rice fields in Khammouan province, Lao PDR

We surveyed Nongceng, a village in a south-eastern province of Lao PDR, for malaria and its vectors. Nongceng is situated in a basin and surrounded by rice fields. In February 1998 (dry season), 28.6% of 126 villagers were in fected with malaria, and in September 1998 (rainy season), 16.3% of 147 vil lagers. The prevalence of malaria infection was consistently high in childr en under 10, and the predominant malaria species was Plasmodium falciparum. In brief surveys of the mosquitoes performed on the same day as the malari a surveys, 2007 Anopheles females from 12 species were collected by means o f human bait, animal bait and resting collections. Of the vector species kn own to be important in transmitting malaria in neighbouring Thailand - An. minimus, An. dirus, and An. maculatus groups - only An. minimus was found. Its density was, however, very low in both seasons and it was therefore unl ikely to be the vector. In fact, An. nivipes accounted for more than 65% of all mosquitoes collected and was the most common species collected from hu man baits. The results of this study show that endemic areas of malaria in Lao PDR are not necessarily related to forest. Rather, An. nivipes is suspe cted to be the most important vector.