Pathological and molecular findings associated with BRSV in cattle and buffaloes with pulmonary disease.

Bovine respiratory syncytial virus (BRSV) is an important pathogen affecting the respiratory health of ruminants and causes pulmonary lesions with occasional systemic involvement. This study aimed to detect and characterize BRSV in susceptible hosts exhibiting clinical signs of respiratory distress and pulmonary lesions in Maharashtra, India. A total of 391 samples (295 lung tissues and 96 nasal swabs), were collected from cattle and buffaloes showing respiratory signs and pulmonary lesions. Nested PCR was employed for the molecular detection of BRSV. Gross and histopathological changes were further analyzed in positive cases. The overall incidence of BRSV was 13.55%, with a higher detection rate in buffaloes (27.73%) compared to cattle (9.09%). Clinically, BRSV-positive cases exhibited nasal discharge, cough, fever, wheezing, and conjunctivitis, consistent with respiratory distress. Gross pathological findings included focal to multifocal consolidation in the cranioventral lung regions and emphysema and edema in the caudal lobes. Histopathological examination revealed bronchiolar epithelial necrosis, hyperplasia, neutrophilic and mononuclear infiltration, and the presence of syncytial cells. Molecular characterization demonstrated high genetic similarity among isolates, indicating a common viral strain circulating in the region. However, nucleotide variations, leading to nonsynonymous amino acid changes, suggested genetic diversity among circulating strains. This study highlights BRSV as a critical respiratory pathogen in cattle and buffaloes, particularly affecting buffaloes with a higher incidence. The findings underscore the need for sustained surveillance, targeted control measures, and vaccine development to mitigate the disease's impact on animal health and productivity. This is the first report of BRSV detection and characterization in Maharashtra, India.