Susceptibility of Culex quinquefasciatus populations to deltamethrin in theSefwi area of the western region of Ghana

Malaria vector control in Ghana includes the use of long-lasting pyrethroid treated nets. The high level of pyrethroid resistance reported in some West African Culex quinquefasciatus (Cx. Quinquefasciatus) populations may impede malaria control operations. The study sought to determine the susceptibility of Culex mosquito populations at Bekwai, Surano, Anwiam and Dwinase in the Sefwi Area of the Western region of Ghana to deltamethrin - a pyrethroid insecticide. Bioassays were performed using WHO diagnostic test kits and procedures on 1–3 days – old unfed female mosquitoes reared from larval collections. The mosquitoes were identified using morphological keys. The results indicate that there was a significant variation in the KDRs between sites with the highest occurring at Surano (100%) and the lowest at Anhwian (69%) [p = 0.001]. Mortalities after 24 hour recovery period were 91%, 93%, 97% and 100% for the Anhwiam, Dwinase, Bekwai and Surano mosquitoes respectively. The results suggest that the Cx. Quinquefasciatus from Surano are highly susceptible to deltamethrin but there may be reduced susceptibility in the mosquitoes from Anhwiam, Dwinase and Bekwai to this pyrethroid, although biochemical assays may be necessary to confirm this observation.