Abstract
Background.Behavioral resilience in mosquitoes poses a significant challenge to mosquito control. Although behavior changes in anopheline vectors have been reported over the last decade, there are no empirical data to suggest they compromise the efficacy of vector control in reducing malaria transmission.Methods.In this study, we quantified human exposure to both bites and infective bites of a major malaria vector in Papua New Guinea over the course of 4 years surrounding nationwide bednet distribution. We also quantified malaria infection prevalence in the human population during the same time period.Results.We observed a shift in mosquito biting to earlier hours of the evening, before individuals are indoors and protected by bednets, followed by a return to preintervention biting rates. As a result, net users and non–net users experienced higher levels of transmission than before the intervention. The personal protection provided by a bednet decreased over the study period and was lowest in the adult population, who may be an important reservoir for transmission. Malaria prevalence decreased in only 1 of 3 study villages after the distribution.Discussion.This study highlights the necessity of validating and deploying vector control measures targeting outdoor exposure to control and eliminate malaria.
Highlights
In the past two decades, global efforts to reduce the burden of malaria have intensified
Control c efforts can result in shifts in vector behaviour and/or species composition such that the posts intervention vector community is less likely to come in contact with insecticide [3–9]. u Studies to accurately quantify exposure to bites and the true protective efficacy of long-lasting n insecticidal nets (LLINs) [10] have revealed that the vast majority of exposure still occurs inside, a when people can be protected by an LLIN [11]
Regardless, in some settings, evidence suggests that these behavioural changes are decreasing the personal protection against bites offered by an LLIN [16], a worrying p prospect for malaria control and elimination in these areas. e It is well established that residual malaria transmission, can be intense
Summary
In the past two decades, global efforts to reduce the burden of malaria have intensified. To estimate the proportion of bites experienced inside and outside, additional collections were t performed in June 2011 During this month, indoor landing catches were performed simultaneously ip with the outdoor landing catches at one chosen household per night for six consecutive nights. Since paired indoor d and outdoor landing catches were not performed during the entire study period, indoor hourly te biting rates were estimated by first calculating the hourly proportions biting inside and outside during the paired collections. Exposure to infective bites was estimated by first calculating the hourly infection rate Nt. Exposure to infective bites for a net-user was ript And for a non-user usc The personal protection against infective bites (P*f) provided by an LLIN was an Bu was compared across years in each village using Kruskal-Wallis tests with pairwise comparisons. All statistical analyses were performed with SPSS 22 (IBM). e Prevalence of malaria positivity was compared between years within each village using chi-square Acc tests
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