Bovine respiratory syncytial virus: First identification in eastern Algeria based on direct immunofluorescence and ELISA tests

Bovine respiratory syncytial virus (BRSV) is the main agent of the bovine respiratory disease complex (BRD). Its circulation among the Algerian bovine population has been strongly suspected but never confirmed. This study investigated the prevalence of BRSV in cattle in eastern Algeria. From 2022 to 2023, a total of 225 serum and 102 lung tissue samples were collected from farms and slaughtered cattle of different ages. Samples were tested for BRSV antibodies by Enzyme-Linked Immunosorbent Assay (ELISA) and BRSV antigens by Direct Immunofluorescence Test (DFAT). Histopathological examination was also performed on lung tissue sections. BRSV-specific antibodies were detected in 91.11% (205/225) of serum samples, while only 27.45% (28/102) of lung tissue sections harbored the BRSV antigen. Only a few BRSV-positive cattle lungs had syncytial cells. BRSV positivity rates by ELISA and DFAT were not age-related (P>0.05). On the contrary, semi-quantitative ELISA titers were significantly higher (P<0.01) in adult cattle (82.25%) than in young cattle (73.00%). Finally, for the 102 cattle concurrently tested by ELISA and DFAT, the BRSV positivity rate yielded by ELISA was higher (95% vs 27.45%). This discrepancy highlights variations in the temporal dynamics of BRSV infection within the studied cattle population. The high seroprevalence of BRSV in subclinically infected cattle in eastern Algeria suggests that the virus is endemic in the study region's cattle populations. This represents the first epidemiological study on the prevalence of BRSV in Algeria. Further research is needed to better determine how the virus spreads throughout the country.