Effect of washing on the bioefficacy of insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) against main malaria vector Anopheles stephensi by three bioassay methods.

BACKGROUND & OBJECTIVES The use of pyrethoid impregnated bednets is one of the main malaria vector control strategies worldwide. The objective of the present study was to evaluate the bioefficacy of bednets impregnated with various pyrethroids after repeated washings. METHODS The effectiveness of bednets impregnated with permethrin, deltamethrin, bifenthrin, etofenprox and long-lasting bednets like OlysetNet and PermaNet which were provided by WHOPES was evaluated. The tests were carried out according to the WHO-recommended methods. Malaria vector, Anopheles stephensi was exposed to impregnated bednets for 3 min and the mortality was measured after 24 h recovery period. Knockdown was measured as well. RESULTS Results of three methods of bioassay tests showed that between two LLINs, PermaNet was more efficient than OlysetNet. Results of ITNs exhibited that deltamethrin and permethrin were more effective than etofenprox and bifenthrin as impregnants. INTERPRETATION & CONCLUSION Findings of this study will be useful for WHO, local authorities and people who wish to use different pyrethroid-impregnated bednets for malaria vector control.