The use of permethrin-impregnated bednets for malaria control in coastal Tanzania: Preliminary entomological impact on vectors

A community-based malaria control programme, using permethrin-impregnated mosquito nets (IMNs) was carried out in the Bagamoyo District, coastal Tanzania. One of the aims of the programme was to determine whether sufficient protection could be achieved to reduce malaria transmission. We report on the relevant entomological aspects before and after intervention. The study was conducted in an area with high malaria transmission, with estimated entomological inoculation rates (EIR) of 300 infective bites per person per annum. After two and a half years of using IMNs, mosquito densities were not affected but there was a significant reduction in enzyme linked immunosorbent assay (ELISA) sporozoite rates. This led to a reduction of the EIR by 76 % in intervention villages and is mainly due to individual protection. Reduction in EIR was 86 % for Anopheles funestus Giles (Diptera: Culicidae) compared to 66 % for An gambiae s.l. Giles (P \u3c0.001). However, unprotected communities are still at risk from malaria. To realize optimum community protection against malaria, extra effort should be made to maximize net coverage in the community, encourage net use throughout the year and ensure regular and timely re-impregnation of mosquito nets

Vector species composition and malaria infectivity rates in Mkuzi, Muheza District, north-eastern Tanzania

Entomological surveys were conducted in Mkuzi village in Muheza District, north-east Tanzania from April to September 2003. The objectives were to determine the species composition and infectivity rates of mosquitoes in Mkuzi village. Mosquito collection was done using CDC light trap and pyrethrum spray catch (PSC) techniques. The light trap: spray catch ratio was 2.2:1. A total of 2157 mosquitoes were collected (light trap= 1483; PSC= 674). Anopheles gambiae s.s. accounted for 56.7% (N=1224) of all mosquitoes collected. Other species were An. funestus complex (19.2%) and Culex quinquefasciatus (24.1%).The mosquito density per room was 74.15 and 33.7 for light trap and PSC techniques, respectively. A total of 1637 Anopheles mosquitoes were tested for circumsporozoite protein by Enzyme linked Immunosobent Assay (ELISA). The overall infectivity rate for circumsporozoite protein for P. falciparum in Anopheles mosquitoes was 21.14% (346/1637). Species-specific infectivity rates were 22.7% (278/1224) in An. gambiae s.s. and 24.0 % (68/283) in An. funestus funestus, 0% (0/80) for An. rivulorum and 0% (0/50) for An.parensis. Blood meal analysis indicated that 92.3 % of An. gambiae s.s, 88.9% of An. funestus s.s., 64.5% of An. rivulorum and 67.7% of An. parensis had taken blood meal from human hosts. In conclusion, malaria transmission in Mkuzi area of Muheza district is mainly by the highly anthropophagic An. gambiae s.s. and An. funestus s.s. More studies are needed to identify the seasonal variation of species composition and transmission dynamics in this village