Molecular investigation and phylogeny of Theileria spp. from naturally infected sheep and the first report of Theileria sp. OT3 in Sulaymaniyah governorate/Iraq.

Abstract

Theileriosis is a significant hemoprotozoal disease of domestic and wild ruminants in tropical and subtropical regions of the world. Ovines are mainly infected by T. ovis and T. lestoquardi, causing economic losses. Due to data scarceness in the Sulaymaniyah governorate, north of Iraq, this study was conducted to investigate subclinical theileriosis using microscopic examination and PCR. A total of 450 blood samples were collected from eight districts in Sulaymaniyah. The samples were randomly taken from clinically healthy sheep in 40 farms from April to Octo- ber 2017. Following the organism verification, PCR products were sequenced and aligned. The study results revealed that 76.0% (n=342) and 58.0% (n=261) of the examined samples were positive for Theileria spp. by PCR and microscopic examination. T. ovis was reported in 76.0% (n=342) of all tested samples, while T. lestoquardi was present in 28.4% (n=97) of the positive specimens. Higher infection rates were observed during July and August. Analysis of the 18S rRNA gene partial sequence of the studied isolates with corresponding sequences in GenBank showed high degrees of identities with T. ovis and T. lestoquardi isolates reported from Iraq and other countries. T. uilenbergi and T. sp. OT3 were detected only through analysis of obtained partial sequences from Theileria-positive samples. Following analysis, T. uilenbergi isolates represented a high homology degree with Theileria isolates from Iraq and China. The newly identified T. sp. OT3 showed >99% identity with T. sp. OT3 isolates of Chinese and Spanish origin.