Two species of T. lestoquardi and T.ovis caused ovine theileriosis in Iran. T. lestoquardi is as agent of malignant form that was reported from south and south east of Iran. T.ovis as a benign form was distributed in all areas of country. Iran with different climates can directly affect geographical distribution of every tick borne diseases. A molecular study was done to detect of Theileria species and tick vectors in sheep of different climatic areas of Iran. A total of 410 sheep from different flocks were clinically examined and collected blood samples and ticks from 2010 to 2011. The blood smears were stained by Geimsa. The collected ticks were also identified based on ticks’ keys and separated into tick pools according to their species and sexes. Then, their salivary glands and ovaries were dissected out in 0.85% saline under stereomicroscope. DNA of blood samples and salivary glands of ticks were extracted by using a DNA extraction kit and examined by using seminested- PCR. A rate of piroplasms infection was microscopically detected in 22%, 55%, 46% and 17.5% of sheep in Caspian, mountainous, semidesrt and desert climates , respectively. By using seminested-PCR, infection with both Theileria species was detected in blood of sheep in each climate. T.ovis, T.lestoquardi and mixed infection were detected in 32- 63%, 0.83-38% and 9.1- 38% of blood samples in different climates. In this study, both Theileria spp infections were detected in salivary glands of R.turanicus of all climates except Caspian climate and H. marginatum of mountainous climate. Based on obtained results, it is concluded that T.ovis and T.lestoquardi were prevalent in sheep in all climatic condition, although the frequency of T.ovis was higher than T.lestoquardi in sheep of every climates. It seems that R, turanicus and H.marginatum could be as vectors of both Theileria species in Iran.

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