objective To assess the susceptibility status of malaria vectors to pyrethroids and
dichlorodiphenyltrichloroethane (DDT), characterise the mechanisms underlying resistance and
evaluate the role of agro-chemical use in resistance selection among malaria vectors in Sengerema
agro-ecosystem zone, Tanzania.
methods Mosquito larvae were collected from farms and reared to obtain adults. The susceptibility
status of An. gambiae s.l. was assessed using WHO bioassay tests to permethrin, deltamethrin,
lambdacyhalothrin, etofenprox, cyfluthrin and DDT. Resistant specimens were screened for knockdown resistance gene (kdr), followed by sequencing both Western and Eastern African variants. A gas
chromatography–mass spectrophotometer (GC-MS) was used to determine pesticide residues in soil
and sediments from mosquitoes’ breeding habitats.
results Anopheles gambiae s.l. was resistant to all the insecticides tested. The population of
Anopheles gambiae s.l was composed of Anopheles arabiensis by 91%. The East African kdr
(L1014S) allele was found in 13 of 305 specimens that survived insecticide exposure, with an allele
frequency from 0.9% to 50%. DDTs residues were found in soils at a concentration up to 9.90 ng/g
(dry weight).
conclusion The observed high resistance levels of An. gambiae s.l., the detection of kdr mutations
and pesticide residues in mosquito breeding habitats demonstrate vector resistance mediated by
pesticide usage. An integrated intervention through collaboration of agricultural, livestock and vector
control units is vital
German Academic Exchange programme (DAAD) and the Consortium for Advanced
Research Training in Africa (CARTA)