Effects of permethrin-treated uniforms on tick submissions to a military passive tick surveillance program

Permethrin-treated clothing is often recommended as a first line of defense against tick-borne diseases. In 2012, the permethrin factory-treated Army Combat Uniform was first made available to active duty Soldiers, Army National Guard, Army Reserve Enlisted Soldiers, and the Senior/Junior Reserve Officers Training Corps. Subsequently, Air Force and Marine Corps personnel were also offered permethrin factory-treated uniforms. Here, we use the passive surveillance data collected through the Military Tick Identification/Infection Confirmation Kit (MilTICK) program to determine the effectiveness of permethrin-treated uniforms at protecting Department of Defense personnel from exposure to tick-borne pathogens in the United States. We analyzed whether submissions by self-reported users of the permethrin-treated uniforms had smaller proportions of engorged ticks, certain cohorts of MilTICK users were better protected than others, and specific tick species were better repelled than others. We found that permethrin use resulted in significantly lower proportions of engorged ticks submitted across MilTICK users. Army and Army National Guard personnel reported more permethrin-treated uniform use than other services. For submissions from active duty personnel serving in uniform, the proportion of tick engorgement in the presence of permethrin increased over time, possibly indicating that permethrin-treated uniforms suffer from reduced performance over the life of the garment. We also found that while permethrin reduced all tick species' ability to feed until engorgement or repletion, blacklegged tick adult females were better able to resist permethrin's lethal effects than lone star tick and American dog tick adult females. Permethrin-treated clothing plays an important role in keeping military personnel safe from tick-borne diseases.