A lethal ovitrap‐based mass trapping scheme for dengue control in Australia: II. Impact on populations of the mosquito Aedes aegypti

Abstract

In Cairns, Australia, the impacts on Aedes aegypti L. (Diptera: Culicidae) populations of two types of 'lure & kill' (L&K) lethal ovitraps (LOs), the standard lethal ovitrap (SLO) and the biodegradable lethal ovitrap (BLO) were measured during three mass-trapping interventions. To assess the efficacy of the SLO, two interventions (one dry season and one wet season) were conducted in three discrete areas, each lasting 4 weeks, with the following treatments: (i) SLOs (>200 traps, approximately 4/premise), BG-sentinel traps (BGSs; approximately 15, 1/premise) and larval control (container reduction and methoprene treatment) and (ii) larval control alone, and (iii) untreated control. Female Ae. aegypti populations were monitored for 4 weeks pre- and post-treatment in all three areas using BGSs and sticky ovitraps (SOs) or non-lethal regular ovitraps (ROs). In the dry season, 206 SLOs and 15 BGSs set at 54 and 15 houses, respectively, caught and killed an estimated 419 and 73 female Ae. aegypti, respectively. No significant decrease in collection size of female Ae. aegypti could be attributed to the treatments. In the wet season, 243 SLOs and 15 BGSs killed approximately 993 and 119 female Ae. aegypti, respectively. The mean number of female Ae. aegypti collected after 4 weeks with SOs and BGSs was significantly less than the control (LSD post-hoc test). The third mass-trapping intervention was conducted using the BLO during the wet season in Cairns. For this trial, three treatment areas were each provided with BLOs (>500, approximately 4/premise) plus larval control, and an untreated control area was designated. Adult female Ae. aegypti were collected for 4 weeks pre- and post-treatment using 15 BGSs and 20 SOs. During this period, 53.2% of BLOs contained a total of 6654 Ae. aegypti eggs. Over the intervention period, collections of Ae. aegypti in the treatment areas were significantly less than in the control area for BGSs but not SOs. An influx of relatively large numbers of young females may have confounded the measurement of changes in populations of older females in these studies. This is an important issue, with implications for assessing delayed action control measures, such as LOs and parasites/pathogens that aim to change mosquito age structure. Finally, the high public acceptability of SLOs and BLOs, coupled with significant impacts on female Ae. aegypti populations in two of the three interventions reported here, suggest that mass trapping with SLOs and BLOs can be an effective component of a dengue control strategy.

Evaluation of the Effectiveness of Mass Trapping With BG-Sentinel Traps for Dengue Vector Control: A Cluster Randomized Controlled Trial in Manaus, Brazil

“…Furthermore, during the second rainy season, the declined number of participating households might have contributed to the absence of a signiÞcant effect of mass trapping. Our observation concerning the lack of a treatment effect during the dry season concurs with the results of Rapley et al (2009), where an effect of LO mass deployment (in combination with larvicides and BGS in some houses) was observed during the wet season, but not during the dry season.…”

“…aegypti strain to the used deltamethrin treated oviposition strips might have inßuenced the results (Ocampo et al 2009). In Australia, the effect of LO mass deployment when used in combination with larvicide application and the use of BGS in a few premises was shown during the wet season but not during the dry season (Rapley et al 2009). Thus, it corroborates with our observations.…”

“…In studies in Brazil and Thailand, LOs (10 per house) were installed in all designated treatment houses Sithiprasasna et al 2003). In Australia, Rapley et al (2009) reported participation of 71Ð75% of households in two LO mass deployment experiments of 1 mo. In a Þeld trial to evaluate the effectiveness of insecticide treated curtains for dengue vector control, 79.7% of households used treated curtains in the beginning of the study, but by the end of the 18 mo study period this number decreased to 32.3% (Vanlerberghe et al 2011).…”

“…LOs have also been used in combination with source reduction, biological larval control (Bti and Mesocyclops), and insecticide-treated jar covers at seropositive dengue foci in Thailand ( Kittayapong et al 2008). Rapley et al (2009) evaluated a mass trapping scheme, where lure-and-kill using LOs was combined with larval control and the use of BG-Sentinel (BGS) traps in some premises. The study designs of the abovementioned reports are different and the results are inconsistent; however, all studies demonstrated a reduction of Ae.…”

Aedes aegypti (Diptera: Culicidae): evaluation of natural long-lasting materials containing pyriproxyfen to improve control strategies

“…Different devices have been studied and are now commercialized. In some of them, the rough egg-laying wooden paddle was replaced by a velour paper strip treated with an insecticide like deltamethrin or bifenthrin while others added a sticky surface Williams et al 2007;Ritchie et al 2008Ritchie et al , 2009Rapley et al 2009;Chadee and Ritchie 2010). The newest ones make them more attractive to oviposit (Attractant-Bait Lethal Ovitrap ALOT) in which the ovitrap is filled with water laced with attractants and the container is lined with a fabric impregnated with an insecticide to kill the adults when they land to oviposit their eggs (Wesson et al 2012).…”