Field and laboratory studies on the use of malathion for control of body-lice in Egypt.

In view of the development of resistance to DDT by Egyptian strains of body-lice, there is a need for another effective and safe insecticide with which they may be controlled. Trials were made in three governorates of the United Arab Republic to compare the effectiveness against these insects of 1% malathion and 10% DDT dusts, 30 g of powder being applied inside the clothing while it was being worn.When susceptibility tests were carried out with the WHO standard technique, the LC(50) was found to be less than 0.04% malathion. In the field, 1% malathion could effectively control lice for three weeks after one application.The 10% DDT dust was less effective, the lice in all three areas showing varying degrees of resistance. However, this insecticide is still considered to be reasonably effective for louse control in central Egypt; in Fayoum Governorate, it might be used but two applications would be needed; north of the Delta its effectiveness appears very doubtful.