Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Insecticidal resistance profiles of an Aedes aegypti (Linnaeus) strain from the Caribbean region of Costa Rica.

Abstract

Introduction: Dengue is the main vector-borne disease in Costa Rica. The control of the vector Aedes aegypti covers the application of pyrethrins and temephos. For this reason, it is important to monitor the development of resistance to these insecticides. Material and Methods: Bioassays were performed using Ae. aegypti larvae from the county of Guacimo in the Caribbean region of Costa Rica. Twenty-larvae groups were exposed to insecticidal concentrations for 24 hours, which would generate 2 to 100% mortality. The tests were performed five times, and a 50% lethal concentration (LC50) was calculated. The Rockefeller strain was used as susceptibility control. A 50% resistance ratio (RR50) was calculated for each insecticide. When resistance occurred, tests were repeated by exposing the larvae to piperonyl butoxide (PB) and S,S,S,tributylphosphorotrithioate (DEF) in order to determine the enzymatic mechanism associated with this resistance. Results: No resistance to temephos or deltamethrin was observed, but emerging resistance to cypermethrin was detected (LC50=0.00845 mg/L, range from 0.00664 to 0.01038, RR50=6.07). The synergistic analysis determined a synergism ratio (SR) of 19.2 for PB and 0.9 for DEF. Conclusions: These results show that there is a process of developing resistance to cypermethrin in Ae. aegypti mosquitoes of this county, which is associated with cytochrome P450 monooxygenase activity. This alerts authorities to the need of replacing this insecticide and ensure the appropriate vector control without generating resistance.