DDT Powder for the Control of Lice Attacking Man1

Abstract

DDT was tested first against lice at the Orlando, Fla., laboratory of the Bureau of Entomology and Plant Quarantine in Nov., 1942, and a louse powder was recommended to the armed forces in May, 1943. In arm-and-leg tests powders containing 5% DDT were effective against body lice for 14-16 days and those containing 10% DDT gave complete kill for 30-40 days. In tests on grossly infested subjects a 10% DDT powder gave practically complete kill of lice for 3 weeks. All the lice exposed to a 10% DDT powder were knocked down in 6 hrs. and were dead in 20 hrs. Tests with various diluents indicated that pyrophyllite and certain grades of talc were the most suitable. Dusts made of pyrophyllite of particle size of 5 u or less were more effective than those made with diluent of larger particle size. A powder containing 10% DDT did not lose its effectiveness after several months'' exposure to the open air or when stored at 60[degree] C (140[degree] F) for 2 months. However, after 10 months'' exposure to 60[degree] C, it lost about half of its toxicity. 10% DDT powder was found highly effective against crab lice.