Анотация: To identify the prevalence rate of theileria annulata, blood and lymph node biopsy smears and blood and lymph node PCR have been developed. In 174 out of 1202 blood samples (14.478 percentage) and in 129 out of 1202 lymph node biopsy samples (10.73 percentage), the piroplasm forms and macroschizonts of Theileнria were observed on blood and lymph node biopsy smears, respectively. A 230 bp band in both PCR tests that indicated the presence of T. annulata (prevalence rate) was present in 338 out of 1202 samples (28.11 percentage). Statistical analysis showed significant differences (P<0.01) between the ability of biopsy smears and PCR tests to detect T. annulata. Our study entirely rejected the presence of the other Theileria species as parasitic pathogens in southwest Iran. After analysis of data, it was recognized that 14.47 percentage and 8.23 percentage of positive samples were on late and initial stages of disease, respectively. It was estimated that 32.24 percentage of positive samples have been treated. Application of both PCR tests was more sensitive than the two other diagnostic assays to detect T. annulata. To our knowнledge, this study is the first report of direct identification of T. annulata in blood and lymph node samples by evaluation of biopsy smears and PCRs tests in Iran