A case of acute respiratory disease associated with Bovine Coronavirus (BCoV) infection in calves at the cattle farm in eastern Poland

Bovine Respiratory Disease Complex (BRDC) and Neonatal Calf Diarrhea (NCD) are the two most important syndromes responsible for the majority of mortality cases in calves. They have a complex etiology with multiple viral agents involved, including Bovine Coronavirus (BCoV). Respiratory and enteric signs were observed in 11 calves newly introduced into a herd in eastern Poland. Within two weeks, eight fatal cases were noticed. Results of an on-site antigenic serological test performed by a veterinary surgeon on one of the calves, pointed to a possible BCoV infection. To confirm involvement of this virus, samples from seven affected animals were subjected to testing using real time RT-PCR and RT-PCR assays specific to BCoV. To exclude other potential respiratory and enteric viral pathogens, additional real time PCR tests were performed for Bovine Viral Diarrhoea Virus (BVDV), Bovine herpes virus – 1 (BoHV-1) and Bovine respiratory syncytial virus (BRSV). Genetic material of BCoV was detected in all tested animals by RT-PCR and in 6 out of 7 by real time RT-PCR, while no samples were positive for BVDV, BoHV-1 or BRSV. Sequence analysis of BCoV isolates showed their close relation to each other and to the Polish strains identified in recent years. Our results confirmed that BCoV could be a causative factor of fatal cases in calves even in absence of other viruses involved. They also point to the need to quarantine calves before introduction into the herd, and monitor their health.