Influence on sensitivity to insecticides: a case study of a settled area and a game park in Liwonde.

The close proximity of Liwonde National Park to Liwonde town creates a unique situation of a large human population adjacent to a natural undisturbed animal reserve. The closeness of the two ecosystems has an impact on biology of mosquitoes of the area, such as susceptibility to insecticides. Susceptibility to insecticide was determined using knockdown bioassays. The mosquito, Anopheles gambiae, was exposed to 0.05% deltamethrin and 0.75% permethrin giving LT 50 and LT 90. The LT50 values for A. gambiae from the town was 17.23 minutes and those from the park, 14.7 minutes (p < 0.05). The calculated LT 90 values were 32.8 and 28.3 minutes respectively. These results suggest that human settlements using insecticides in mosquito control reduce susceptibility of mosquitoes to regularly used insecticides such as deltamethrin and permethrin in this study.