Pyrethroids and DDT tolerance of Anopheles gambiae s.l. from Sengerema District, an area of intensive pesticide usage in north-western Tanzania.
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.



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 knock-down 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.



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).



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.
Mkwawa University College of Education, Private bag, Iringa, Tanzania.
Anitha
A
Philbert
University of Dar es Salaam, Dar es Salaam, Tanzania.
Sylvester Leonard
SL
Lyantagaye
Division of Cellular and Applied Infection Biology, Institute of Zoology, RWTH Aachen University, Aachen, Germany.
Gabriele
G
Pradel
Division of Cellular and Applied Infection Biology, Institute of Zoology, RWTH Aachen University, Aachen, Germany.
Che Julius
CJ
Ngwa
University of Dar es Salaam, Dar es Salaam, Tanzania.
Gamba
G
Nkwengulila
D000383:Agriculture; D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000235:genetics; D003634:DDT / Q000494:pharmacology*; D017753:Ecosystem; D017344:Genes, Insect; D006801:Humans; D007303:Insect Vectors / Q000187:drug effects* / Q000235:genetics; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D008288:Malaria / Q000635:transmission*; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D026023:Permethrin / Q000494:pharmacology; D010573:Pesticide Residues; D010575:Pesticides / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology*; D012987:Soil / Q000737:chemistry; D013045:Species Specificity; D013636:Tanzania
D007306:Insecticides; D009570:Nitriles; D010573:Pesticide Residues; D010575:Pesticides; D011722:Pyrethrins; D012987:Soil; C076840:ethofenprox; C017180:decamethrin; D026023:Permethrin; D003634:DDT; C052570:cyfluthrin; C037304:cyhalothrin
Agricultura; Piretroides; Resistencia; Sengerema; Tanzania; Tanzanie; agriculture; malaria; malaria vectors; pyrethroids; pyréthroïdes; resistance; résistance; vecteurs du paludisme; vectores de Malaria