Studies on the Biology and Behaviour of the Mosquito Anopheles Arabiensis Patton (Diptera: Culicidae) In Eastern Sudan-New Halfa Town

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Yousif El Safi, Hemeidan
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The biology and behaviour of An. arabiensis and its susceptibility to insecticides were studied in two localities at New Halfa town (Dibaira camp and Hei Elmasakine), during March 1999 to June 2000. Four methods were adopted: standard dipper for larval survey, hand capture, knock down and human baits for collection of adults. Of 4854 mosquitoes collected by pyrethrum spray and hand capture, 4847 (99.86%) were An. arabiensis and 7 (0.14%) were An. pharoensis. Female mosquitoes were captured throughout the year, but their abundance was related to the annual rainfall and irrigation period of the agricultural scheme. Two peaks of densities of both immature and adult stages were observed: the major one occurred in September (110.3 females/room/day and 84.7 larvae/l0 dips) and the minor one occurred in December (15.1 females/room/day and 36.2 larvae/l0 dips). The main breeding sites of An. arabiensis in the study area were water bodies resulting from leakage of pipes (82.49% of total larvae collected). Anopheles arabiensis were found to bite human baits mostly out-doors rather than indoors (p<0.001). The peak of biting activities occurred between 18.00-20.00 hrs outdoors and between 20.00-22.00 and 02.00-06.00 hrs indoors. The average man biting rate of An. arabiensis was 6.23 bites/man/night in Dibaira camp and 4.94 bites/man/night in Hei Elmasakine. The percentage of parity rate during the rainy season was 32.23%. An. arabiensis in the area was mostly anthropophilic (78.72% fed on human blood). The duration of egg-adult life-cycle of An. arabiensis in the rainy season was 8.5 days, while in cool season the egg-adult life-cycle was 22.5 days. Susceptibility of An. arabiensis to DDT 4%, Malathion 5% and fenitrothion 1 % was 97.8%, 99.1 % and 100% respectively. The prevalence of malaria from November-June ranged from 3.6 to 12.8% with high infection rate in children of 2-9 years (61.6%). A minor peak occurred in January and a major one in October. P. falciparum constituted 70.7% of infection while P. vivax constituted 29.3%.
Studies on the Biology and Behaviour of the Mosquito Anopheles Arabiensis Patton