Ticks and tick-borne diseases, including theileriosis, constitute a major constraint to livestock production. Two species, known as Theileria lestoquardi and Theileria ovis, are suspected to contribute to ovine theileriosis in Iran. However, the epidemiological aspects of ovine theileriosis are poorly understood in this country. In a survey, designed to identify Theileria species in sheep, 52 (...