A Serological Study on Bovine Leukemia Virus Infection in Some Provinces of Iran between 2010 and 2012

Bovine leukaemia virus (BLV) is an oncogenic member of the genus Deltaretrovirus of the family Retroviridae. BLV is the causative agent of enzootic bovine leukaemia and infects cattle worldwide, imposing economic impact on the dairy cattle industry. The purpose of this study was to estimate the seroprevalence of BLV in cattle in some provinces of Iran. A total of 280 cows over 2 years old from 10 provinces of Iran in different regions and environments from industrial and less industrial herds were used in the study. Blood samples of all cows were taken both with and without EDTA. Serum separation for the ELISA test and leukocyte count, were performed upon receipt without delay. Cattle without fever that had lymphocyte numbers of more than 9,000/μl were suspected to have persistent lymphocytosis (PL). Sera samples were examined for antibodies against BLV by blocking ELISA. The seroprevalence of BLV among animals was 32.8% and among provinces was 80%. Seropositive cattle had higher total leukocyte and lymphocyte count and lower neutrophil count than seronegative cattle (P<0.001). Among BLV seropositive animals, the rate of PL was 36.9%. None of the seronegative animals showed lymphocytosis. Comparing the data with previous studies on seroprevalence of BLV in different localities in Iran, the prevalence of the infection has been raised. These results suggest that promoting control programs in Iran are very important. Furthermore, it will be essential to conduct nationwide surveillance program and determine the major risk factors.