Variation in temephos resistance in field populations of Aedes aegypti (Diptera: Culicidae) in the State of Sergipe, Northeast Brazil.

INTRODUCTION

The organophosphate temephos was first used in Brazil in the 1960s for the control of Aedes aegypti. Because of its extensive and longstanding use worldwide, selection for mosquito populations resistant to the chemical has been observed not only in different regions of Brazil but also in several parts of the world. The objective of this study was to evaluate the susceptibility of Ae. aegypti to the organophosphate temephos, a larvicide used in vector control activities in Sergipe/Northeast Brazil.

METHODS

This study included mosquito populations from seven municipalities of Sergipe and was carried out from October 2010 to August 2011. Qualitative bioassays of diagnostic dose and dose responses were performed. The resistance ratio was calculated based on lethal concentrations for mosquitoes of the susceptible Rockefeller strain.

RESULTS

All populations were classified as resistant to temephos. The resistance ratio ranged from 22.2 to 297.9, the lowest being seen in Aracaju, a coastal area of the state, and the highest in Pinhão, a semi-arid region, 96.6km from Aracaju.

CONCLUSIONS

High levels of temephos resistance were observed in the Ae. aegypti populations of Sergipe. The variation between regions indicates that there have been different regimes of insecticide use and also points to the potential of small cities to generate and spread insecticide resistance.