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A study on adult anopheline ecology and malaria vector incrimination was carried out from 1986 to 1989 during irrigation development in an area of the Mahaweli Project in eastern Sri Lanka. Eleven potential vector species were collected resting indoors or by using human or bovid bait, and from light trap catches. Overall, Anopheles vagus (Donitz), An. annularis (van der Wulp), and An. subpictus (Grassi) were the most prevalent, and An. culicifacies (Giles) and An. barbirostris (van der Wulp) were the least prevalent species. The abundance of An. aconitus (Donitz), An. jamesii (Theobald), An. pallidus (Theobald), and An. subpictus increased after irrigation development, while An. annularis, An. barbirostris, An. culicifacies and An. varuna (Iyengar) decreased. Populations of An. nigerrimus (Giles), An. tessellatus (Theobald), and An. vagus did not change substantially. Seven species were infected with malaria parasites, as determined by enzyme-linked immunosorbent assays (ELISA) done on mosquito head-thorax triturates. The main species involved were An. annularis, at peak abundance during the 1986-1987 period of development leading to the onset of irrigation, and An. subpictus, during times of seasonal abundance in the post-irrigation period of 1988 to 1989. Although occurring at low abundance, An. culicifacies was involved in malaria transmission irregularly throughout the study period. While there was strong ELISA-based evidence implicating An. subpictus as a major post-irrigation vector, confirmation of its vector status must await dissection and ELISA-based evidence of P. vivax and P. falciparum sporozoite infection rates in salivary glands.

N,N-diethyl-3-methylbenzamide (DEET) has recently been reported to kill cercariae of Schistosoma mansoni in vitro. In addition, it blocked cercarial entry into mouse tail skin. We confirmed these results and compared the efficacy of DEET to a second insect repellent, 1-(3-Cyclohexen-1-yl-carbonyl)-2-methylpiperidine (AI3-37220), in preventing S. mansoni infections in mice. Both AI3-37220 and DEET conferred 100% protection against S. mansoni infection via percutaneous exposure to cercariae.