Bovine leukemia virus (BLV), the causative agent of enzootic bovine leukosis, is an exogenous, B-Lymphotropic retrovirus belonging to the Orthoretrovirinae subfamily and the retroviridae family that induces persistent lymphocytosis (PL) in cattle. This survey investigated the presence of anti-BLV antibodies and BLV provirus in Babol small province (North of Iran) cattle blood samples. In this survey, sampled from 6 herds of Babol small province industrial dairy cattle emphasis randomly sampling. A total of 234 whole blood samples from cattle were studied. An enzyme linked immune sorbent assay (ELISA) was used to detect anti- BLV antibodies and nested PCR was employed to increase of care in all cattle blood samples specially the samples that shown doubtful serological results obtained by ELISA. Then epidemiological aspects of BLV are reviewed with emphasis on diagnostic tests (ELISA and nested PCR). Overall prevalence of anti-BLV antibodies in dairy cattle blood samples were 0% and 15.38%, respectively. When using ELISA as a gold standard, sensitivity and specificity for nested PCR were 100% and 97%, respectively. The predictive value of a positive test was 70% and the predictive value of a negative test was 100%. Interpretation of kappa scores for two methods accounted substantial 0.85. The percentage of accuracy between two tests accounted 97%. We find a direct relationship between aging and percent of infection (p<0.05) and also between number of parturition and percent of Infection (p<0.05).
