Repellency of permethrin-treated battle-dress uniforms during Operation Tandem Thrust 2001

Successful feeding by mosquitoes through permethrin-treated battle-dress uniforms (BDUs) was observed in the Shoalwater Bay Training 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 60%, 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). Treated, 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 from bothersome mosquitoes and the associated risk of mosquito-borne 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.