Spatial repellents are essential for personal protection against mosquitoes that bite and transmit disease pathogens to humans. Current repellent screening methods, such as olfactometers and alternative choice tests, are complex systems that require a large quantity of compound (mg). This study validates a high-throughput spatial repellent screening method that occupies relatively little space and requires small amounts of compound (typically µg). Specifically, treated filter papers (5 cm2) are held in caps on both ends of a 12.5 cm glass tube, and groups of mosquitoes (n = 16) are prevented from contacting the filter paper by netting. Spatial repellency is quantified by the proportion of mosquitoes on the treated side of the test tube. In this system, DEET had an EC50 (half effective repellent concentration on the filter paper) values of 31 (25-39) µg/cm2 against Ae. aegypti wild-type (OR) susceptible strain. Screening of experimental fluorinated phenylamides identified several compounds with activity comparable to DEET (EC50 values, µg/cm2, in parentheses): 1-4A (25), 4-2B (15), 4-3D (17), and 4-5A (17). Three anthranilate compounds also showed strong spatial repellency; ethyl anthranilate was most active, with an EC50 of 7 µg/cm2 on OR, ca. 4-fold lower than DEET. A slightly modified version of the assay gave an EC50 for transfluthrin of 0.5 and 2.3 µg/cm2 in susceptible OR and pyrethroid-resistant PR strains, respectively (4.6-fold resistance). The setup can also be used for assessing vapor toxicity. Transfluthrin-exposed OR strain had 1 hr KC50 value of 0.7 µg/cm2 and 24 hr LC50 value of 0.15 µg/cm2. The PR strain was 43-fold more resistant in 1 hr knockdown (KC50 = 30 µg/cm2) and 53-fold more resistant in 24 hr mortality (LC50 = 7.9 µg/cm2). To conclude, this high-throughput screening setup is useful for assessing fast-acting candidate spatial repellents and quantification of vapor toxicity against mosquitoes.

High-throughput screening apparatus for evaluating spatial repellency and vapor toxicity of commercially available and candidate repellent compounds

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.