Susceptibility of body-lice to DDT in a heavily treated area of Yugoslavia.

Body-lice collected in the Kosohovo-Metohia area of Yugoslavia, an area with a long history of epidemic typhus and one which had been treated with DDT since 1947, were tested for their susceptibility to that compound by the standard WHO test and showed an average mortality of 99% to 1.0% DDT and 96% to 0.1% DDT. Freshly fed insects showed 100% mortality at both concentrations. Tests with DDT-impregnated cloth indicated that the LD(50) had tripled between 1955 and 1958.In sleeve tests the body-lice appeared to tolerate 15 times as much DDT as in tests not involving the use of the human arm. Tests were also made to ascertain the effect of lowered temperature on reducing mortality from DDT, and the speed of kill with DDT was compared with that with BHC and pyrethrins.