Shayan et al. : Molecular Study of Sheep Malignant Theileriosis… The DNA was extracted from the sent sam- ples and amplified using common primers designed from 18S rRNA gene of Theileria spp. These primers can amplify simultane- ously Theileria spp. and Babesia spp. The PCR products of Theilera spp. and Babesia spp. were 426-430 bp and 389-402 bp, respectively. The PCR analysis showed an expected PCR product of 428 bp in length in DNA prepared from liver, lung, and lymph node (Fig. 1 D).The PCR product was puri- fied and sequenced and was registered under accession number JF309152 in GenBank. Sequence analysis showed 99% homology to the registered in GenBank for T. lestoquardi under accession numbers: gb|AY260185.1, gb|AY260184.1, gb|AY260183.1, gb|AF- 081135.1|AF081135). The Theileria sp. iso- lated in Barka region in the Sultanate of Oman differed from the above-mentioned sequences only in one nucleotide at position 254. The nucleotide sequence at position 254 in Theileria sp. isolated in Barka region in the Sultanate of Oman was A whereas in other sequences for T. lestoquardi was G. The above mentioned nucleotide sequence also showed 99 percent homology to the T. annulata sequence data registered under accession numbers gb|GU233775.1, gb|GU233773.1, gb|GU2-24091.1, gb|GU- 129923.1, gb|GU129921.1, gb|FJ426369.1, gb|EU083801.1, gb|EU08-3800.1, gb|EU- 083799.1, gb|EU407241.1, gb|AY524666.1, gb|AY508473.1 in GenBank. The sequence differed from the mentioned genes only in one nucleotide sequence at position 225 (T/C). The Oman sequence had 94% homol- ogy to the T. ovis registered also in GenBank under accession numbers gb|FJ752026.1, gb|FJ603460.1, gb|EU-622911.1, gb|EF- 092453.1, gb|EF09-2452.1, gb|AY533144.1, gb|AY260173.1, gb|AY-260172.1, gb|AY- 508461.1, gb|AY50-8460.1, gb|AY508459.1, gb|AY508458.1. The Oman sequence also had 92% homology to the T. china1 and T. china 2 sequence registered in GenBank under accession numbers AY262119 and AY262121. Fig. 1: Giemsa staining from impression smears were prepared from lung (A), spleen (B) and lymph node (C). DNA was extracted from the mentioned organs and amplified with primers derived from 18S rRNA gene (lung D1, liver D2, lymph node D3, spleen D4 and negative control D5). 69