Lymphatic filariasis in Ghana: entomological investigation of transmissiondynamics and intensity in communities served by irrigation systems in the Upper East Region of Ghana

We conducted an entomological study to document the effect of irrigation on the vectors and transmission dynamics of lymphatic filariasis in the Upper East Region of Ghana. Mosquitoes were collected by indoor spraying of hous es in a cluster of communities located around irrigation projects (Tono and Vea) and others without reservoirs (Azoka). Anopheles gambiae s.s. was the dominant species and major Vector, followed by; An. funestus. Anopheles ar abiensis constituted 9-14% of the An. gambiae complex hut none were infecti ve. Culex quinquefasciatus was also not infective in these communities. Chr omosomal examinations showed that >60% (n = 280-386) of the An. gambiae s.s . in irrigated communities were Mopti forms whilst 73% (n = 224) in the non -irrigated area were Savannah forms. Infectivity rates (2.3-2.8 vs. 0.25), worm load (1.62-2.04 vs. 1.0), annual bites per person (6.50-8.83 vs. 0.47) and annual transmission potential (13.26-14.30 vs. 0.47) were significantl y higher in irrigated communities.