Cattle kept at the Latoli kraal of the Indian Veterinary Research Institute at Mukteswar in the Kumaon foothills of the Himalayas were heavily infested with the tick Boophilus microplus (Can.). In order to reduce the infestation, the animals were treated with BHC dusts every season for a number of years. In 1960, it was noticed that the treatment was not as effective as in the previous years. A series of concentration/response tests was therefore carried out in 1961–62 to see whether or not the tick had developed any resistance to BHC. Ticks collected from cattle in a village about five miles distant, where no acaricide had ever been applied, were used as the standard for comparison. BHC as a wettable powder was used to provide six different concentrations of γ BHC for engorged females and unfed larvae, respectively. Treatment was by appropriate dipping techniques. Analysis of the results showed that the population of B. microplus infesting cattle at the Latoli kraal had developed resistance to BHC. The LC50's of γ BHC for engorged females and unfed larvae, respectively, of the Latoli population were 0.5164 and 0.0182 per cent., and of the village population 0.0834 and 0.00069 per cent. This seems to be the first record of any species of tick developing resistance to an acaricide in India.
It was found that the mean number of eggs laid per tick in the control batches was higher in the village population than in the Latoli population and that the difference was highly significant.