Seasonal distribution of Theileria in Hyalomma anatolicum anatolicum ticks of an endemic area of Haryana, India.

The effect of season on the capacity of Hyalomma anatolicum anatolicum ticks to transmit Theileria was studied by detecting Theileria sporoblasts in the salivary glands of 647 adult ticks moulted in winter (November 1990 to March 1991) and 677 adult ticks moulted in the summer-rainy season (June to August 1991). The intensity (number of infected acini per infected tick) and abundance (number of infected acini per tick examined) of Theileria sporoblasts were significantly (P < 0.05) higher in winter moulted ticks (10.75 and 2.23 respectively) than the summer-rainy season moulted ticks (7.31 and 1.77 respectively). The prevalence of infected moulted ticks was not significantly higher in the summer-rainy season (24.22%) than in the winter (20.71%). A higher percentage of winter moulted ticks had high numbers of infected acini (> or = 11/infected tick) than the summer-rainy season moulted ticks, while the trend was reversed for low numbers of infected acini(5/infected tick), being 47.76% for winter and 73.78% for the summer-rainy season. It was concluded that the winter of Haryana is more favourable to the developing theilerial stages in the ticks than the summer-rainy season.