Effects of sublethal exposure to metofluthrin on the fitness of Aedes aegypti in a domestic setting in Cairns, Queensland

Buhagiar, Tamara S., Devine, Gregor J., and Ritchie, Scott A. (2017) Effects of sublethal exposure to metofluthrin on the fitness of Aedes aegypti in a domestic setting in Cairns, Queensland. Parasites & Vectors, 10 (274). pp. 1-7.

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Background: Metofluthrin is highly effective at reducing biting activity in Aedes aegypti. Its efficacy lies in the rapid onset of confusion, knockdown, and subsequent kill of a mosquito. In the field, there are a variety of scenarios that might result in sublethal exposure to metofluthrin, including mosquitoes that are active at the margins of the chemical's lethal range, brief exposure as mosquitoes fly in and out of treated spaces or decreasing efficacy of the emanators with time. Sublethal effects are key elements of insecticide exposure and selection.

Methods: The metofluthrin dose for each treatment group of male and female Ae. aegypti was controlled using exposure time intervals to a 10% active ingredient (AI) metofluthrin emanator. Room size and distance from the emanator for all groups was maintained at 3 m. In bioassay cages, male Ae. aegypti were exposed at 0, 5, 10, 20, 30 and 40-min intervals. Females were exposed in bioassay cages at 0, 10, 20, 30, 40 and 60-min intervals. Mortality rates and fecundity were observed between the exposure time groups for both sexes.

Results: Female Ae. aegypti exposed for 60 min had a significantly higher mortality rate (50%), after a 24-h recovery period, than other exposure times, 10, 20, 30 and 40 min (P < 0.001). An overall difference in fecundity was not observed in females between treatments. A significant effect on male mortality was only observed at 40 min exposure times, three meters from the 10% AI emanator (X−=98%,P<0.001). Males that survived metofluthrin exposure were as likely to produce viable eggs with an unexposed female as males that had not been exposed (P > 0.05).

Conclusion: Regardless of sex, if a mosquito survived exposure, it would be as biologically successful as its unexposed counterpart. Portability of the metofluthrin emanator and delayed knockdown effects create opportunities for sublethal exposure and potential pyrethroid resistance development in Ae. aegypti, and should be taken into consideration in recommendations for field application of this product, including minimum exposure periods and a prescribed number of emanators per room based on volume.

Item ID: 49201
Item Type: Article (Research - C1)
ISSN: 1756-3305
Keywords: metofluthrin, spatial repellents, pyrethroid-resistance, Aedes aegypti, dengue
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© The Author(s). 2017 Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Funders: Deployed Warfighter (DW), National Health and Medical Research Council of Australia (NHMRC)
Projects and Grants: DW Deployment Grant #W911QY-15-1-0006, NHMRC Senior Research Fellowship 1044698
Date Deposited: 07 Jun 2017 02:29
FoR Codes: 42 HEALTH SCIENCES > 4203 Health services and systems > 420315 One health @ 100%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920499 Public Health (excl. Specific Population Health) not elsewhere classified @ 100%
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