Theileria species are common in tropical and subtropical regions and cause great economical losses in ruminants. Two species, T. lestoquardi and T. ovis, are suspected to cause ovine theileriosis in Iran. The epidemiological aspects of ovine theileriosis in Iran are poorly understood and further investigations by sensitive and precise techniques are required. In a previous study, a sensitive and specific PCR-RFLP method was used for the identification of Theileria spp. in sheep. In the present study, Theileria species involved in ovine theileriosis were determined in five different regions in eastern half of Iran (Zabol, Lar, Ferdows, Semnan and Gorgan). Blood samples were collected in EDTA. Of 220 blood samples obtained from sheep in different regions, 60% (132.220) were positive for Theileria spp. by nested-PCR compared with 22.27% (49.220) by microscopic examination. Using RFLP of PCR products, out of 132 positive blood samples, 55.3% (73.132) were positive for T. lestoquardi and 44.7% (59.132) were positive for T. ovis. The infection with these two Theileria species in different areas is compared in the article. This is the first report in which ovine theileriosis has been studied in different regions in Iran using molecular identification techniques.

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