Interventions that effectively target Anopheles funestus mosquitoes could significantly improve control of persistent malaria transmission in south–eastern TanzaniaReport as inadecuate




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Malaria is transmitted by many Anopheles species whose proportionate contributions vary across settings. We re-assessed the roles of Anopheles arabiensis and Anopheles funestus, and examined potential benefits of species-specific interventions in an area in south-eastern Tanzania, where malaria transmission persists, four years after mass distribution of long-lasting insecticide-treated nets LLINs. Monthly mosquito sampling was done in randomly selected households in three villages using CDC light traps and back-pack aspirators, between January-2015 and January-2016, four years after the last mass distribution of LLINs in 2011. Multiplex polymerase chain reaction PCR was used to identify members of An. funestus and Anopheles gambiae complexes. Enzyme-linked immunosorbent assay ELISA was used to detect Plasmodium sporozoites in mosquito salivary glands, and to identify sources of mosquito blood meals. WHO susceptibility assays were done on wild caught female An. funestus s.l, and physiological ages approximated by examining mosquito ovaries for parity. A total of 20,135 An. arabiensis and 4,759 An. funestus were collected. The An. funestus group consisted of 76.6% An. funestus s.s, 2.9% An. rivulorum, 7.1% An. leesoni, and 13.4% unamplified samples. Of all mosquitoes positive for Plasmodium, 82.6% were An. funestus s.s, 14.0% were An. arabiensis and 3.4% were An. rivulorum. An. funestus and An. arabiensis contributed 86.21% and 13.79% respectively, of annual entomological inoculation rate EIR. An. arabiensis fed on humans 73.4%, cattle 22.0%, dogs 3.1% and chicken 1.5%, but An. funestus fed exclusively on humans. The An. funestus populations were 100% susceptible to organophosphates, pirimiphos methyl and malathion, but resistant to permethrin 10.5% mortality, deltamethrin 18.7%, lambda-cyhalothrin 18.7% and DDT 26.2%, and had reduced susceptibility to bendiocarb 95% and propoxur 90.1%. Parity rate was higher in An. funestus 65.8% than An. arabiensis 44.1%. Though An. arabiensis is still the most abundant vector species here, the remaining malaria transmission is predominantly mediated by An. funestus, possibly due to high insecticide resistance and high survival probabilities. Interventions that effectively target An. funestus mosquitoes could therefore significantly improve control of persistent malaria transmission in south–eastern Tanzania.



Author: Emmanuel W. Kaindoa , Nancy S. Matowo, Halfan S. Ngowo, Gustav Mkandawile, Arnold Mmbando, Marcelina Finda, Fredros O. Okumu

Source: http://plos.srce.hr/



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