Abstract
BackgroundSpatial repellents that drive mosquitoes away from treated areas, and odour-baited traps, that attract and kill mosquitoes, can be combined and work synergistically in a push-pull system. Push-pull systems have been shown to reduce house entry and outdoor biting rates of malaria vectors and so have the potential to control other outdoor biting mosquitoes such as Aedes aegypti that transmit arboviral diseases. In this study, semi-field experiments were conducted to evaluate whether a push-pull system could be used to reduce bites from Aedes mosquitoes.MethodsThe push and pull under investigation consisted of two freestanding transfluthrin passive emanators (FTPE) and a BG sentinel trap (BGS) respectively. The FTPE contained hessian strips treated with 5.25 g of transfluthrin active ingredient. The efficacies of FTPE and BGS alone and in combination were evaluated by human landing catch in a large semi-field system in Tanzania. We also investigated the protection of FTPE over six months. The data were analyzed using generalized linear mixed models with binomial distribution.ResultsTwo FTPE had a protective efficacy (PE) of 61.2% (95% confidence interval (CI): 52.2–69.9%) against the human landing of Ae. aegypti. The BGS did not significantly reduce mosquito landings; the PE was 2.1% (95% CI: −2.9–7.2%). The push-pull provided a PE of 64.5% (95% CI: 59.1–69.9%). However, there was no significant difference in the PE between the push-pull and the two FTPE against Ae. aegypti (P = 0.30). The FTPE offered significant protection against Ae. aegypti at month three, with a PE of 46.4% (95% CI: 41.1–51.8%), but not at six months with a PE of 2.2% (95% CI: −9.0–14.0%).ConclusionsThe PE of the FTPE and the full push-pull are similar, indicative that bite prevention is primarily due to the activity of the FTPE. While these results are encouraging for the FTPE, further work is needed for a push-pull system to be recommended for Ae. aegypti control. The three-month protection against Ae. aegypti bites suggests that FTPE would be a useful additional control tool during dengue outbreaks, that does not require regular user compliance.
Highlights
Spatial repellents that drive mosquitoes away from treated areas, and odour-baited traps, that attract and kill mosquitoes, can be combined and work synergistically in a push-pull system
The protective efficacy (PE) of freestanding transfluthrin passive emanators (FTPE) against Ae. aegypti bites was 61.0% (95% Confidence interval (CI): 52.2–69.9%; odds ratio (OR): 0.14, 95% CI: 0.12–0.16, P < 0.0001) (Fig. 3, Table 1)
The BG sentinel trap (BGS) did not reduce Ae. aegypti landings on a human volunteer sitting 10 m away with PE of 2.1% (Fig. 3)
Summary
Spatial repellents that drive mosquitoes away from treated areas, and odour-baited traps, that attract and kill mosquitoes, can be combined and work synergistically in a push-pull system. Push-pull systems have been shown to reduce house entry and outdoor biting rates of malaria vectors and so have the potential to control other outdoor biting mosquitoes such as Aedes aegypti that transmit arboviral diseases. Dengue vector control is centered on larval source management, treatment of resting surfaces with insecticides and with space spraying as a response to disease outbreaks [5]. Personal protection measures are recommended during disease outbreaks through the use of appropriate clothing or topical repellents [6]. Topical repellents such as DEET (N, N-diethyl-m-toluamide) have demonstrated efficacy in reducing mosquito bites [7], and are recommended for arbovirus prevention among military personnel and travelers [8]. Each of the current control tools for Aedes has clear limitations and the development of complementary control tools to help fill these gaps is needed
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