Abstract: The efficacy of a spatial repellent may depend upon the structure of the protected area. For example, some spatial repellents may work best in enclosed spaces, while others perform better in open areas. We deployed the spatial repellent transfluthrin using a system of small polypropylene 3D-printed capsules containing cotton wool substrate in two different scenarios at Camp Blanding in Starke, FL, to determine how well each performed at reducing mosquito trap collections, and whether performance may vary by species. The first scenario was comprised of one-person US Marine Corps tents, with the capsules containing transfluthrin hung in the open doorway and a CO2-baited CDC trap with light suspended inside from the middle of the tent roof. The second scenario consisted of a series of open-topped enclosures constructed of metal poles wrapped in US Army camouflage netting material on four sides, with the capsules containing transfluthrin strung across the top opening and a CO2-baited CDC trap with light suspended in the center of the enclosure. In both scenarios, trapping for mosquitoes was conducted for one night approximately once a week, followed by identification and tallies of all collections to species, and calculation of percent reduction in collections for each scenario relative to collections in untreated controls. We found that transfluthrin substantially reduced collections in open-topped camouflage netting enclosures yet either had no effect or increased collections in the confines of small one-person tents. Moreover, we found that the efficacy of transfluthrin in reducing collections varied in some cases depending on the target species. These results provide evidence that implementation of spatial repellents should not be universal but rather should be balanced by knowledge of efficacy in the use scenario and against specific targets.
