Evaluating the efficacy of DEET-based topical repellent products against biting midges using a modified arm-in-cage method

Biting midges ( Culicoides spp.) are vectors of filarial parasites and arboviruses like Oropouche virus, as well as major nuisance biters to humans and animals. Personal protection, including the use of topical repellent, is essential to preventing infective bites. However, no standardised methods exist for testing the efficacy of topical repellent products for humans against biting midges. We have developed, validated, and conducted a modified arm-in-cage (AIC) test with human participants to evaluate the complete protection time of seven insect topical repellent products containing 9.5%, 20%, and 50% DEET at the recommended product application rates. Landing rates, equivalent to those typically observed in the field, were successfully achieved on the untreated forearm, validating the AIC assay before assessing protection on the treated forearms. The 9.5% DEET product demonstrated a complete protection time (CPT) of 07:02 h. Among the 20% DEET formulations, the roll-on recorded the highest CPT of 09:32 h, whereas the 50% DEET roll-on recorded the highest CPT of 10:36 h overall. In conclusion, this modified AIC test method simulates field testing, whilst providing a safe approach for the efficacy evaluation of topical repellents for human use against biting midges. The CPT values obtained for the tested products demonstrate their efficacy in protecting humans against midge bites.