Abstract
Background:
Ovine and caprine theileriosis is a tick-borne hemoprotozoan disease, caused by Theileria spp., responsible for heavy economic losses in terms of high mortality and morbidity rates. Diagnosis of ovine theileriosis is primarily based on clinical symptoms, microscopic screening of stained blood smears and lymph node biopsy smears, but the limitations of these detection methods against Theileria spp. infection limit their specificity.
Aim:
To overcome these limitations, the current study reports the differential diagnosis of theileriosis through Blood Smear Examination and Polymerase Chain Reaction in small ruminants from Pakistan.
Methods:
The study was conducted on 1200 apparently healthy small ruminants (737 sheep and 463 goats). Firstly, blood smears were screened for the presence of Theileria piroplasms in red blood cells. Secondly, PCR amplification based on 18S rRNA gene was performed by using primers specific to Theileria spp.
Results:
Out of 1200 small ruminants, 100 were positive for Theileria genus by blood smears microscopy while 315 samples were found positive by PCR. The sensitivity and specificity rates were 26.98 % and 98.31 % for blood smear method, and 73.01% and 100 % of PCR assay, respectively.
Conclusion:
Our finding suggests that PCR is the gold standard method compared to the conventional method of smear examination for the diagnosis of ovine and caprine theileriosis in Pakistan.

Key words: Ovine and caprine theileriosis, Differential diagnosis, Microscopic screening, PCR assay, Pakistan.