Insecticide susceptibility evaluation in Aedes aegypti populations of Caldas, Colombia, in 2007 and 2011

Abstract

Introduction: Continuous use of insecticides for the control of dengue transmission may lead to decreased susceptibility levels in mosquito vector populations. Timely monitoring is necessary to ensure detection of any potential resistance problems.

Objective: To determine the susceptibility status of Aedes aegypti to insecticides used in public health in Caldas, Colombia, during 2007 and 2011.

Materials and methods: Susceptibility tests to the organophosphates temephos, malathion, fenitrothion and pirimiphos methyl, as well as to the pyrethroid deltamethrin, were carried out using standard World Health Organization and Centers for Disease Control and Prevention protocols.

Results: In 2007, resistance to temephos was detected in Ae. aegypti populations from La Dorada with resistance ratios of 11.5 and 13.3, prompting the Caldas Health Department to suspend the use of this larvicide. A reduction in resistance ratios to temephos was observed in 2011, as well as an apparent resistance to pirimiphos methyl. All Ae. aegypti populations tested were susceptible to deltamethrin, malathion and fenitrothion in both years.

Conclusion: Evaluating the resistance ratios during two distinct periods allowed a decrease in resistance to be detected after suspension of the use of temephos. Surveillance of mosquito populations for changes in susceptibility levels to the insecticides used in dengue control programs is therefore recommended.