Distribution of the members of Anopheles gambiae and pyrethroid knock-down resistance gene (kdr) in Guinea-Bissau, West Africa
Dabiré, K.R.; Diabaté, A.; Agostinho, F.; Alves, F.; Manga, L.; Faye, O.; Baldet, T.
Bulletin de la Societe de Pathologie Exotique 101(2): 119-123
2008
ISSN/ISBN: 0037-9085 PMID: 18543705 Document Number: 619246
An entomological survey conducted in 2002 in Guinea Bissau aimed to study the distribution of the members of Anopheles gambiae Giles complex (Diptera: Culicidae) throughout four ecological areas extended from mangrove to savannah; to evaluate the insecticide susceptibility status of these malaria vectors exposed to permethrin (0.75%) and DDT (4%); and to investigate the occurrence and the spread of the Leu-Phe knock down resistance (kdr) gene associated with pyrethroid and DDT resistance within these vector populations. Adult female mosquitoes issued from indoor morning collections were tested using WHO procedures, test kits and impregnated papers to assess their insecticide susceptibility status. The tested specimens were identified by PCR assays and characterized for the kdr gene. Malaria vectors were mainly dominated elsewhere by A. gambiae s. s. (both S and M molecular forms) living in sympatry with low proportion of A. melas in littoral areas. A. gambiae s. s. tested populations were fully susceptible both to permethrin 0.75% and DDT 4% irrespective of their location and ecotypes. The Leu-Phe kdr mutation was detected at a low frequency only in two sites respectively urban (Bissau) and Guinea-savannah (Gabu) areas. It occurred only in the S molecular form in Gabu (at the frequency of 0. 4) and both in the S and M molecular forms in Bissau at the frequency of 0.06 and 0.02, respectively. These results suggested that the populations of A. gambiae s. s., the most frequent malaria vector in Guinea Bissau, still remain cross-susceptible to pyrethroids and DDT. This susceptibility status and the frequency of resistance mechanism such as the kdr mutation must be monitored in the future particularly in the urban and savannah areas with continuous and intensive use of insecticides.