Screening of insecticide resistance in Aedes aegypti populations collected from parishes in Eastern Jamaica.

Abstract

Owing to the increased reports in Aedes-borne diseases in the Caribbean and Latin America, the United States Agency for International Development assisted the Jamaican Ministry of Health and Wellness in conducting insecticide susceptibility tests on Aedes aegypti populations. Sentinel sites were established in seven parishes of Jamaica (St. Catherine, Kingston and St. Andrew, St. Thomas, Portland, St. Mary and St. Ann) and Aedes aegypti eggs were collected, reared to adults per collected population and their susceptibility to varying pyrethroids and organophosphates were tested using the World Health Organization paper bioassays for these insecticides. The Centers for Disease Control and Prevention bottle bioassay was used to assess susceptibility to the carbamate, bendiocarb. The voltage gated sodium channel gene mutations V1016I and I1011V, normally associated with pyrethroid resistance, were also analysed. The results showed that Aedes aegypti collected from all parishes exhibited resistance to pyrethroids at the following concentrations, permethrin 0.25-2.5%; deltamethrin 0.03-0.15%; lambda-cyhalothrin 0.03-0.3%; and etofenprox 0.5-2.5%. The insecticide deltamethrin at concentration 0.3% was the only pyrethroid tested that resulted in high mortality, 94.9 ± 0.34% knockdown within 1 hour of exposure and 98.95 ± 0.01% mortality (p <0.01) at 24 hours post exposure. The frequency of the voltage gated sodium channel gene mutation V1016I was high in the tested population, possibly accounting for the reduced sensitivity to pyrethroids. Organophosphate resistance was also observed in all populations tested. Mortality rates for 0.8% Malathion was 0.8 ± 0.70-60.68 ± 0.38% after 24 hour and 0.00-47.10 ± 3.02%, for pirimiphos-methyl 0.21%. Bendiocarb applied as 12.5 μg/ bottle resulted in mortality rates of 76.25 ± 4.30-100 ± 0.00% after 30 minutes of exposure. The results showed that Ae. aegypti from the seven parishes analysed demonstrated resistance to the insecticides tested. Deltamethrin and bendiocarb at concentrations 0.3% and 12.5μg respectively, were considered most effective, causing high mortality in the local populations. Routine monitoring and evaluations of Ae. aegypti populations from the included parishes are recommended. Additionally, the study results represent the most comprehensive testing to date with local Aedes aegypti populations distributed across different parishes of Jamaica and should be useful to guide national and sub national strategies for vector control and surveillance.