Prevalence of BRD-Related Viral Pathogens in the Upper Respiratory Tract of Swiss Veal Calves

SIMPLE SUMMARY: In bovines, infection of the respiratory tract is frequent. It may lead to severe disease and death, and often requires antimicrobial treatment. Antimicrobial treatment is known to be related to antimicrobial resistance, which poses a threat to public health; therefore, efforts to better understand the causes of airway infection must be undertaken. Many different pathogens may be responsible for disease onset, including viruses. The aim of this study was to describe the prevalence of respiratory viruses in Swiss veal calves and to identify risk factors for infection. In a convenience sample of 764 swabs, prevalence rates were determined for bovine respiratory syncytial virus (BRSV, 2.1%), bovine parainfluenza-3 virus (BPI3V, 3.3%), bovine coronavirus (BCoV, 53.5%), influenza D virus (IDV, 4.1%), and influenza C virus (ICV, 0%). Due to the high prevalence rate, risk factors were investigated for BCoV. Younger calves tested positive more frequently than older calves. Increasing group size was associated with increasing probability for occurrence of BCoV. To summarize, different viral pathogens circulate in veal calves. ABSTRACT: The prevention of bovine respiratory disease is important, as it may lead to impaired welfare, economic losses, and considerable antimicrobial use, which can be associated with antimicrobial resistance. The aim of this study was to describe the prevalence of respiratory viruses and to identify risk factors for their occurrence. A convenience sample of 764 deep nasopharyngeal swab samples from veal calves was screened by PCR for bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (BPI3V), bovine coronavirus (BCoV), influenza D virus (IDV), and influenza C virus (ICV). The following prevalence rates were observed: BRSV, 2.1%; BPI3V, 3.3%; BCoV, 53.5%; IDV, 4.1%; ICV, 0%. Logistic mixed regression models were built for BCoV to explore associations with calf management and housing. Positive swab samples were more frequent in younger calves than older calves (>100 days; p < 0.001). The probability of detecting BCoV increased with increasing group size in young calves. Findings from this study suggested that young calves should be fattened in small groups to limit the risk of occurrence of BCoV, although an extended spectrum of risk factors for viral associated respiratory disorders such as nutritional aspects should be considered in future studies.