Discussion
HDN, bite
This study evaluated the performance of two different mosquito trapping methods, the HLC and the HDN, for estimating the effect on mosquito landing rates of two intervention types characterized by contrasting modes of action. The study results indicated that the primary mode of action of each intervention had a substantial impact on how the HDN performed in comparison to the HLC to evaluate the protective efficacies of the VPSR and the etofenprox-treated clothing. The VPSR works primarily through non-contact irritancy; mosquitoes move away from the VPSR or become incapacitated at a distance from the VPSR, without coming into physical contact with the treated substrate. In contrast, Eto R primarily works through contact irritancy, requiring tarsal contact with the treated surface for mosquitoes to be affected by the active ingredient.When evaluating the VPSR intervention, the direction of the estimated effects of the intervention on mosquito landing is similar when measured by HLC and by HDN. However, the HDN intervention arm collected zero mosquitoes, which meant that a precise effect could not be estimated. This observation suggests that a larger number of replicates than the eight included in this study would be necessary when using the HDN to estimate the impact of a VPSR. However, given the magnitude of the observed efficacy, it can be concluded that the HDN remains a suitable collection method for evaluating the protective efficacy of VPSRs.When evaluating the Eto R intervention, there was no evidence of an effect of Eto R on mosquito landing obtained via HDN. In contrast, when using the HLC, the estimated effect of Eto R demonstrated a strong reduction in mosquito landing. The HDN is not a suitable collection method for ITCs likely because this intervention functions primarily through contact irritancy, which requires mosquitoes to physically land on the treated material worn by the collector to then be repelled by the active ingredient [To date, mosquito landing is the accepted endpoint to evaluate the impact of bite prevention tools on human-vector exposure [While there is the opportunity to conduct HLCs in a safe manner using disease-free mosquito populations in the SFS, there remains a pressing need to validate alternative methods to HLCs for evaluating ITCs and VPSRs, particularly outside the SFS, as many countries do not permit HLCs in the field. A limitation of this study is that this evaluation was conducted with a single species (Finally, this study could be further strengthened by conducting evaluations throughout the life of the VPSR intervention so that more reliable estimates of comparative efficacy can be made as the product wanes in efficacy and, presumably, more mosquitoes are captured. As VPSR efficacy wanes and more mosquitoes are attracted to the host, it is possible the estimated protective efficacy via HDN indicates less protection against mosquito landing than the estimated protective efficacy via HLC. This is because the HDN’s inner netting enclosure might further concentrate the VPSR’S active ingredient within the netting enclosure around the collector, interfering with the long-range activity of this intervention, thus further decreasing the number of attracted mosquitoes compared to the HLC [