Tests on Clothing impregnated with DDT as an anti-louse Measure

Abstract

Simple tests have been done to appraise the value of garments impregnated with DDT as an anti-louse measure. It is very toxic to the body louse but its action is relatively slow. Woollen and cotton fabrics can be impregnated with it.No estimate can be given of the precise length of the insecticidal life of a garment because of variations in wear, etc. But garments have been found to have o·1 per cent. DDT remaining after five launders and three weeks' wear. The minimum safe degree of impregnation as an anti-louse measure appears to be o·1 per cent. By the use of simple biological tests reasonably accurate assessments of the chemical content of garments can be made.DDT is to some extent resistant to high temperatures. It is suggested that the chief cause of loss of insecticidal power is due to loss of nap. Impregnated garments transfer their insecticidal power to uriimpregnated garments kept in contact with them.Results show that subsequent mortality is complete or very high among lice which have crawled for three hours on fabrics impregnated with DDT at rates between o·1 and 1·75 per cent. Signs of poisoning may take six hours to be manifested in the louse.The results obtained with a sleeve test compared very closely with those obtained by the box method used chiefly in this work.The theory is put forward that DDT enters the body louse through its tactile sense organs.