A Within-subject Laboratory and Field Trial to Test the Use of Commercially Available Insect Repellents Against Contact From Musca Sorbens, the Putative Vector of Trachoma

Musca sorbens, a fly that feeds from ocular and nasal discharge on humans, is thought to be the vector of trachoma. We are developing methods of fly control that specifically target this species, in the hope of interrupting Ct transmission. To our knowledge, the use of commercially available insect repellents has never been tested for prevention of Musca sorbens fly-eye contact (i.e. nuisance and landing in the peri-ocular area). Given the likely necessity for prolonged and/or high frequency fly-eye contact for Ct transmission, the reduction of these contacts through the use of fly repellents presents an exciting opportunity for disease control. Here we propose a within-subject, non-masked, trial of the use of commercially available insect repellents against Musca sorbens, with two consecutive participant groups in the laboratory and in the field, and a primary endpoint of measuring the protective efficacy of each repellent product. Repellent products will be chosen from: DEET (N,N-diethyl-3-methylbenzamide), IR3535 (3-[N-butyl-N-acetyl]-aminopropionic acid ethyl ester), Picaridin (2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester); PMD (para-Menthane-3,8-diol) or permethrin (m-Phenoxybenzyl)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate). Products tested will be either (1) topical repellents, or (2) in long-lasting, plastic formulations of repellents that can be worn on the body (wearable repellent technologies). The insect repellent synergist Vanillin (4-Hydroxy-3-methoxybenzaldehyde) may be added to the long-lasting plastic formulations, to improve the duration of protection.