Effect of passive zooprophylaxis on malaria transmission in the Gambia

The effect of zooprophylaxis on malaria transmission has not been studied o n the African continent despite that the World Health Organization has reco mmended this intervention method since 1982. The effect of passive zooproph ylaxis on malaria vector abundance, mosquito feeding preferences, and infec tivity was studied in an area of moderate seasonal transmission in The Gamb ia. A paired cohort of 204 children <7 yr of age was selected and matched i n groups for presence or absence of cattle (Bos taunts) within 20 m of thei r bedroom. Comparisons were made between mosquitoes collected froth the bed rooms of the two groups of children. Other ruminants and equines were prese nt in both groups of compounds. Most of the anopheline mosquitoes (98.5%) c ollected were Anopheles gambiae sensu lato. There was no difference in the geometric mean number of An. gambiae s.l. mosquitoes caught in houses near or far from cattle. The species composition of the Art. gambiae complex was similar in both groups. Blood meal analysis of specimens collected in hous es without cattle showed a human blood index (HM) of 82% for An. Arabiensis (Patron), 56% for An. gambiae sensu stricto (Giles), and 36% for Anopheles Melas (Theobald), indicating that each of these sibling species fed readil y on animals. The presence of cattle reduced the HBI of An, arabiensis but did not significantly alter the HBI of An. gambiae s.s. or Art. melas. Ther e was no significant difference between the groups in the sporozoite rates of An. gambiae s.l. nor hi the estimated malaria transmission risk. These f indings suggest that passive zooprophylaxis using cattle does not alter the individual exposure to malaria parasites in The Gambia.