The effectiveness of pre-impregnated permethrin in military clothing in the prevention of insect bites

Abstract

Abstract Introduction When on operational deployment, or where a vector-borne disease threat has been identified, military personnel wear uniform that has been pre-impregnated with permethrin insecticide to prevent insect bites, as part of an integrated approach to bite avoidance in order to reduce disease non-battle injury. This article reports a study that was carried out to investigate whether the clothing treatments currently in use are effective at preventing insect bites. Methods A human volunteer study was conducted using two different species of mosquito and clothing subjected to different washing schedules. The number of landing events and probing events, and insect mortality, were recorded. Results There was a marked increase in mosquito activity as the amount of viable permethrin was reduced through washing. There was a statistically significant difference between 50 washes and the negative control, and between 50 and 5 washes. As clothing is increasingly washed, its effectiveness is reduced. Conclusion The use of pre-impregnated uniform does not provide complete protection against biting insects throughout the life of the garment. No single means of protection will prevent personnel from being bitten, and a suite of personal and communal measures should be employed to reduce the risk of vector-borne disease, including the use of insect repellent, mosquito nets, anti-malarial chemoprophylaxis and re-treatment of clothing against biting insects in order to reduce the risk of disease transmission. Since this study, alternative means of clothing treatment have been sought to reinforce the pre-treated uniforms issued. Advice and direction is available, specific to the environment personnel are deploying to, based upon risk.