Reducing biting rates of Aedes aegypti with metofluthrin: investigations in time and space

Abstract

BackgroundIndoor residual spraying is key to dengue control in Cairns and other parts of northern Queensland, Australia, where Aedes aegypti is prevalent, but the strategy faces challenges with regards to slow application time and, therefore, community coverage. A faster potential improvement might be the use of polyethylene netting impregnated with the volatile pyrethroid metofluthrin (SumiOne™). This formulation was assessed in rooms in three houses in Cairns, Australia. One emanator was placed in each room and cages of 10 female Aedes aegypti were exposed at distances of 1 and 3 m. Knockdown and landings on a human hand were counted before metofluthrin exposure and at 10, 30, 60, 90 and 120 min during exposure. In addition, two trials continued over 48 h of exposure to assess the long-term sublethal effects of metofluthrin on caged mosquitoes.ResultsPercentage landing rates fell to 0–2.5% in the first 10 min of exposure. Knockdown was most evident between 10 and 30 min (54% at 1 m and 33% at 3 m). Distance from the emanator strongly affected the results: mosquitoes at 3 m exhibited less knockdown and more landings than those at 1 m. As room volume increased, knockdown decreased and the number of landing increased. There is a cumulative mortality and landing inhibition and, for mosquitoes exposed to metofluthrin for > 48 h, mortality was 100% at 1 m and 90% at 3 m. Of those still alive, a small number continued to land and bite. After being removed from metofluthrin-treated rooms, exposed insect cages were found to reducing landing rates for up to 2 h.ConclusionsDespite only moderate levels of knockdown during the initial hours of exposure, metofluthrin emanators were effective in reducing mosquito landing rates, especially within 1 m, even when exposed on an open veranda. The evaluation methods and results described in this paper will help inform the optimal conditions of deployment of metofluthrin emanators. These devices have the potential to reduce contact between humans and urban disease vectors faster than indoor residual spraying so supplement our current arsenal of dengue control tools.

Model-based analysis of experimental data from interconnected, row-configured huts elucidates multifaceted effects of a volatile chemical on Aedes aegypti mosquitoes

“…These results are in agreement with dose- and distance-dependent effects on knockdown observed upon metofluthrin exposure in Ae. aegypti [ 46 ].…”

Zika prevention: lessons from the Australian front line

“…The new message is supported by an online video demonstrating how to carry out residual spraying in the home 23 . Another new technique currently under evaluation is home metofluthrin emanators 24,25 for distribution to pregnant women. These emanators have been shown to interfere with the biting behaviour of Aedes aegypti 24 …”

A combined experimental-computational approach for spatial protection efficacy assessment of controlled release devices against mosquitoes (Anopheles)

“…In addition, many of these devices require frequent cartridge replacement. Passive emanators using impregnated strips are limited to a single compound showing limited efficacy only for short periods of time [12,13]. Candles are based on essential oils, whose efficacy has been questioned [14].…”