Loss of Biological Efficiency of Cattle-dipping Wash containing Benzene Hexachloride

Abstract

BATHS with capacities of several thousands of gallons are used in the principal cattle-raising countries in the control of ticks on cattle. The cost of the insecticide required to fill these baths is high, and the result is that they are used for one to two years, often longer, without being emptied and cleaned. As it is necessary, particularly in Africa, to dip large numbers of animals frequently, the baths become very foul. In 1946 benzene hexachloride (B.H.C.) was first used in South Africa for control; but its initial efficiency dropped rapidly in several baths, after use for a few months. Whitnall, Bradford, McHardy, Whitehead and Meerholz¹ reported inability to detect alteration in the γ-isomer content of such wash, but “the methods of chemical analyses used in their investigation were not specific for the γ-isomer” (Roulston and Hitchcock²). Technical B.H.C. containing about 13 per cent of the γ-isomer was being used, and the loss of efficiency was not proportional to the loss of total isomers. After fresh insecticide restored initial efficiency, deterioration was then more rapid than before. Similar experience was reported wherever γ-isomer was only slightly in excess of that required for biological control. In Australia, where a much higher concentration was used, loss of efficiency was not observed in the field, although recent determinations by the partition chromatographic method show disproportionate loss of γ-isomer with loss of total isomers. Thus we have found in the B.H.C. contained in six samples from two baths in Queensland 2.9–7.8 per cent γ-isomer. The γ-isomer content of the B.H.C. used for these baths was approximately 12 per cent. Similar results are reported by Roulston and Hitchcock².