Operational Note Repellency of Permethrin-treated B Attle-dres S Uniforms during Operation Tandem Thrust 2oo1

Successful feeding by mosquitoes through permethdn-treated battle-dress uniforms (BDUs) was observed in the Shoalwater Bay Tiaining Area (SWBTA), Queensland, Australia, during Operation Tandem Thrust 1997 (TT97). Therefore, during Operation Tandem Thrust 2001, the repellency of permethrin-treated BDUs was evaluated. Washing permethrin-treated BDUs 1 time reduced the permethrin concentration by 6OVo, but permethrin concentration was not reduced further after subsequent washings (up to 20 times). The probing time of Ochlerotatus vigilax landing on permethrin-treated BDUs was reduced to the greatest extent on the treated, unwashed uniform (7.5-fold reduction). Tieated, washed uniforms also reduced probing time (2.5 times) compared to the untreated control uniform containing no permethrin. Reduced probing time should reduce feeding success and protect operational forces frorn bothersome mosquitoes and the associated risk ofmosquitoborne disease in SWBTA. Observations of successful mosquito feeding made during TT97 could be attributed to the use of old and well-worn BDUs and seasonal differences in mosquito population density.