Intervention description {11a}

Each participant will receive two uniforms, both treated according to the treatment arm. The uniforms will be impregnated with insecticide at Warmkraft–Pine Belt Processing Inc. Participants will wear one of the uniforms all day every day. The second uniform will be worn when the first is being washed. The insecticide in the uniforms will still be viable even after 50 washes [22–24].

No adverse health risks are known to be associated with wearing PTUs. Safety testing of permethrin has been ongoing since the 1970s, following its US Environmental Protection Agency (EPA) registration for use in a variety of applications, including food crops, animal feed crops, livestock, public health mosquito abatement programmes, pets and clothing [25]. Permethrin was first registered for use as a repellent on military clothing in 1990 and is the only insect repellent currently used for factory treatment of clothing. It is a broad-spectrum, non-systemic, synthetic pyrethroid insecticide that targets adults and larvae of many species of biting insects. The EPA has determined that wearing or coming in contact with PTUs for 250 days a year is unlikely to cause adverse health effects [12]. The objective is to provide 90% bite protection for at least 50 launderings, an objective easily met through factory treatment of the army combat uniform (ACU) with permethrin, which demonstrates 99 to 100% bite protection for up to 50 launderings [26].

No adverse health risks are known to be associated with wearing etofenprox-treated clothing. Etofenprox has now received EPA registration for use on military uniforms. The WHO dermal risk assessment for etofenprox is based on a no-observed-adverse-effect level (NOAEL) of 2100 mg/kg/day, which is four times greater than that of permethrin. Uniforms will be factory treated with 0.9% etofenprox. When compared to untreated control fabric, etofenprox-treated fabric demonstrated greater than 90% bite protection after 3 washes [27] and has already been approved for use by US Army personnel.

Each participant from a combania that receives DEET will be given a 120-mL container of 30% DEET repellent (Lipo DEET) for topical application, and the container will be replaced every 2 weeks. Combania in placebo arms will be given 120 mL of placebo lotion. The DEET lotion and its placebo will be prepared by Sawyer Ultra 30. Participants will be instructed to apply the repellent topically twice daily: once in the morning and once in the evening. One application of Lipo DEET protects for up to 12 h and has a pleasant odour and non-greasy feel on the skin. This liposome-based repellent is the newest advance in insect repellent technology. Like the earlier generation of polymer-based controlled release systems, the liposome envelops the active ingredient, DEET, and slowly releases it as needed, thereby extending the repellent’s effectiveness. DEET was selected for this study because it has been extensively tested for safety and toxicity for human use [28–30] and for its efficacy against a broad variety of arthropod vectors [31–33]. DEET was first registered in 1957 and has an excellent safety profile [34, 35].