Field survey of resistance of Anopheles sinensis to deltamethrin in Hubei Province

Aim To understand the resistance of Anopheles sinensis to deltamethrin.Methods Adult Anopheles filter contact method recommended by WHO was used to observe the knockdown rate,the knockdown time of the first Ano pheles and the mortality of the mosquitoes.The resistance level was determined by tentative diagnostic dose and the resistance degree was determned by LD50.Results The knockdown time of the first Anopheles of seven monitoring spots were 10～32min,the knockdown rate of these spots were 3.13 ～18.35% ,KT50 of Anopheles sinensis to deltamethrin were 138.41～6234.72min,an increase of 20～631times than that in 1996;LT50 of Anopheles sinensis of Jingshan county was 684.12min,an increase of 306 times than that in 1998;The discrimination dosage mortality of Anopheles sinensis to deltamethrin were all less than 50%.Conclusion The Anti-knockdown capability and the resistance level of Anopheles sinensis to deltamethrin were both high in Hubei,to guide the use of deltam ethrin.the monitoring work should be strengthened.