Background and Aim: Bovine respiratory syncytial viruses (BRSV) are important causes of acute respiratory disease in postweaning calves and feedlot cattle in the United States and Europe. This disease poses a serious problem due to financial losses caused by animal death, costs of treatment, and subsequent reduced profits. So the aim of this study was evaluate the frequency of respiratory syncytial virus (RSV) in dairy herds in the Chaharmahal va Bakhtyari province - IRAN

Materials and Methods: In this research, 384 serum samples of cattle were collected from Chaharmahal va Bakhtiari provience - Iran and tested by nested RT-PCR. For detection of BRSV genome, at the first viral RNA was extracted by RNX Plus kit (Cinnagen Company) then cDNA was synthesize. Positive control used in this study was the positive control in BioinGentech (Vet PCR^TM Detection Kit). 

Results: A total of 384 serum samples in Chaharmahal va Bakhtiari provience 300 samples were positive in nested RT-PCR. Prevalence rate were determined 78.12%. The highest contamination were reported in Shahrekord city, females and in Winter.

Conclusions: BRSV infection has been reported in all parts of the world. Regardless of geographic location, the prevalence of BIV infection is high. This indicates that the virus is easily transmitted to cattle. These findings are important for effective control management to prevent the spread of the virus that is associated with various methods of agriculture. Therefore, more information to understand the mechanisms of virus survival in a geographic area is required.