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Long-lasting insecticidal screens reduce dengue mosquito vector
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The use of long-lasting insecticidal window screens significantly decreased infestations of the main mosquito vector of dengue virus in Mexico, according to recent findings.
Researchers evaluated the effect of permanently mounted, insecticide-treated screens fitted to doors and windows of homes in Acapulco, Mexico, on infestations of Aedes aegypti. The screens were made of 0.55% wt/wt alpha-cypermethrin–treated nonflammable polyethylene netting, a design approved by the WHO Pesticide Evaluation Scheme.
Using a cluster-randomized sampling design based on previous studies, the researchers identified 20 infestation clusters. These consisted of 10 treatment clusters and 10 control clusters, and 100 households per cluster.
During installation (April-December 2012), households in the treatment arm were advised on maintenance of the long-lasting insecticidal screens (LLIS). No treatment was provided to control homes. The researchers conducted five entomologic surveys of randomly selected houses before intervention and at 5 and 12 months after intervention. In the pre-intervention surveys, 32 houses per cluster were sampled. In the September 2012 survey, 210 houses from treated clusters were sampled, and 302 from control households were sampled; in the March 2013 survey, 311 houses from treated clusters and 320 from control clusters were sampled.
The researchers calculated indices for A. aegypti mosquitoes to quantify house infestation and infestation density for all mosquitoes, all females, all blood-fed females, and males.
On all sampling dates before treatment, indices were similar for both study arms. At 5 months after intervention, significantly fewer treated vs. control houses were infested with A. aegypti adult female mosquitoes (OR = 0.38; 95% CI, 0.21-0.69), blood-fed females (OR = 0.36; 95% CI, 0.21-0.6) and males (OR = 0.39; 95% CI, 0.19-0.77). At 12 months, a significant effect persisted for adult females (OR = 0.41; 95% CI, 0.25-0.68) and males (OR = 0.41; 95% CI, 0.27-0.64) but not for blood-fed females (OR = 0.51; 95% CI, 0.24-1.05). Similarly, analyses of infestation density revealed significantly fewer A. aegypti mosquitoes found in treated vs. control houses.
These findings are encouraging in light of high levels of insecticide resistance in A. aegypti mosquitoesin Acapulco, the researchers wrote.
“We found the use of LLIS was a popular intervention, and perceived efficacy was reinforced by a reduction in other domestic pests,” the researchers wrote. “The likely effects on other peridomestic disease vectors could promote increased adoption of the intervention with additional cost benefits.”
Disclosure: The researchers report no relevant financial disclosures.
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