Widespread Resistance to Temephos in Aedes aegypti (Diptera: Culicidae) from Mexico

Organic synthetic insecticides continue to be part of the arsenal for combating vector-borne diseases in Mexico. Larvicides are a fundamental part of the process in programs for mosquito control, temephos being one of the most widely used in Mexico. In the present study, we analyzed the frequency of temephos resistance in twenty-three Aedes aegypti populations using the discriminating concentration (DC) of 0.012 mg/L. We also tested 5x DC (0.6 mg/L) and 10x DC (0.12 mg/L) of temephos. The resistance distribution to temephos was interpolated to unsampled sites using the inverse distance weighting (IDW) method. The populations of Ae. aegypti showed a high frequency of resistance (1x DC) with mortality rates below 93% in 22 of the 23 populations analyzed. Moderate resistance intensity (5x DC) was found in 78% of the populations, and high intensity (10x DC) in 30%. Predicted mortality was below 60% in the populations of the Pacific Coast, along the Gulf of Mexico, and in the state of Coahuila in Northeastern Mexico in relation to 1x DC; the Pacific Coast and Northeast patterns hold for 5x and 10x DC. The results suggest the need for rotation of the larvicide to effectively control the larval populations of the vector in the country.