Influence of Temperature Change on the Growth and Susceptibility of the Common House Mosquito, Culex pipiens in Egypt to Some Insecticides

By transmitting major human diseases, mosquito species represent a serious threat worldwide in terms of public health. Most vector control programmes aiming to control life-threatening mosquitoes rely on the use of chemical insecticides. For the reason that only a few insecticides are used for public health, maintaining the efficacy of control programmes mostly relies on resistance management strategies. Development of such strategies requires understanding the factors influencing resistance together with characterizing the mechanisms involved. In this context, the present study aims to update current knowledge about the effect of temperature on the mosquito Culex pipiens population response to chemical insecticides. The results demonstrated that alteration of the temperature significantly affects Cx. pipiens populations. High temperature (25, 30°C) resulted in high survival rate (90, 95% respectively); while at temperature 20°C the survival rate was 80%. Egg hatching percentage was 95% after 24 h, at temperature 30°C and 50% after 24h, 50% after 48h at 25°C; however at 20°C egg hatching percentage was 100% after 48 h. In case of Cx. pipiens larvae that were reared under various temperatures pupated on day 5, 9 and 12 at 30°C, 25°C and 20°C, respectively. At high temperature 30°C, females emerged before males. On the other hand resistance of all Cx. pipiens populations to the selected chemical insecticides decreased with raising temperature. The obtained results also showed that there was significant change in acetylcholinesterase and glutathione -S-transferase level in both larvae and adult due to temperature changing. These results indicate that temperature is an important parameter that must be considered during the application of chemical assays or control of Cx. pipiens populations.