Insecticide Resistance in Two <I>Aedes aegypti</I> (Diptera: Culicidae) Strains From Costa Rica

Abstract

Dengue (family Flaviridae, genus Flavivirus, DENV) and dengue hemorrhagic fever (DHF) are presently important public health problems in Costa Rica. The primary strategy for disease control is based on reducing population densities of the main mosquito vector Aedes aegypti (L.) (Diptera: Culicidae). This is heavily dependent on use of chemical insecticides, thus the development of resistance is a frequent threat to control program effectiveness. The objective of this study was to determine the levels of insecticide resistance and the metabolic resistance mechanisms involved in two Ae. aegypti strains collected from two provinces (Puntarenas and Limon) in Costa Rica. Bioassays with larvae were performed according to World Health Organization guidelines and resistance in adults was measured through standard bottle assays. The activities of beta-esterases, cytochrome P450 monooxygenases, and glutathione S-transferases (GST), were assayed through synergists and biochemical tests, wherein the threshold criteria for each enzyme was established using the susceptible Rockefeller strain. The results showed higher resistance levels to the organophosphate (OP) temephos and the pyrethroid deltamethrin in larvae. The efficacy of commercial formulations of temephos in controlling Ae. aegypti populations was 100% mortality up to 11 and 12 d posttreatment with daily water replacements in test containers. Temephos and deltamethrin resistance in larvae were associated with high esterase activity, but not to cytochrome P450 monooxygenase or GST activities. Adult mosquitoes were resistant to deltamethrin, and susceptible to bendiocarb, chlorpyrifos, and cypermethrin. Because temephos and deltamethrin resistance are emerging at the studied sites, alternative insecticides should be considered. The insecticides chlorpyrifos and cypermethrin could be good candidates to use as alternatives for Ae. aegypti control.

Effects of piperonyl butoxide on the toxicity of the organophosphate temephos and the role of esterases in the insecticide resistance of Aedes aegypti

“…Effects similar to the fi ndings presented in this study have been found in various assays showing synergism between low concentrations of PBO and organophosphates in insect species 14,15,20,24,25 . The high level of synergism of 1% PBO in the larvicidal effect of TE has important implications for the control of A. aegypti larvae.…”

“…According to this hypothesis, at 2%, the effects of isomers responsible for the bioactivation of TE increased, offsetting the effect of the isomers involved in metabolic detoxifi cation [18][19][20][21][22] .…”

“…Toxicology assays and investigations of esterases conducted in resistant mosquito strains have indicated that the survivability of these insects is associated with the increased expression of esterases 20 . Similar results have been observed in assays involving other classes of organophosphates 22,23 .…”

Resistance Status of Aedes aegypti to Insecticides in the Jazan Region of Saudi Arabia

“…aegypti was susceptible to it. 13 In this study, Ae. aegypti mosquitoes showed resistance to Lambda-cyhalothrin and DDT, a result which was similarly obtained by other authors in India 11 with the exception only to the susceptibility of Ae.…”

“…aegypti larvae showed higher resistance levels to the organophosphate (OP) temephos and the adult were resistant to deltamethrin, but susceptible to bendiocarb, chlorpyrifos, and cypermethrin. 13 In Havana city, a high resistance of Ae. aegypti larvae to temephos and fenthion was observed.…”