Rotaviruses and Coronaviruses in Calves

Calf Diarrhea Caused by Rotaviruses and Coronaviruses

Rotaviruses and coronaviruses are among the most widespread causes of diarrhea in calves worldwide; they are ubiquitous. They invade and destroy enterocytes. Infections in adult animals are subclinical. Even on farms heavily contaminated with rotaviruses and coronaviruses, the colostrum of dams contains few maternal antibodies if no effective vaccination of the dams was carried out prior to calving. Under high infection pressure, calves become ill as early as 12–72 hours postpartum. They develop thin, porridge-like to watery diarrhea. The degree of systemic distress depends heavily on the severity of the enteritis and the extent of dehydration. In severe cases, calves become bedridden and die.

For this reason, a rapid and timely diagnosis is absolutely essential to prevent severe losses and to contain the spread within the herd as early as possible.

Pathogens and Pathogenesis

Rotaviruses are non-enveloped RNA viruses; Group A is the most clinically significant. Bovine coronaviruses are enveloped RNA viruses. Rotaviruses replicate in the mature, absorptive enterocytes of the small intestinal villi, while coronaviruses additionally damage the epithelium of the large intestine. In both cases, this leads to a shortening of the intestinal villi with a reduced absorption surface area and decreased enzyme activity, resulting in malabsorptive diarrhea.

Transmission within the herd

Transmission occurs via the fecal-oral route and through fecal aerosols; bovine coronaviruses can also be transmitted via respiratory aerosols. Clinically unremarkable adult cattle can shed the virus, with shedding increasing around the time of calving and thus contaminating calving and rearing areas. Rotaviruses and coronaviruses are among the most common pathogens causing neonatal calf diarrhea and frequently occur as mixed infections alongside E. coli K99 and Cryptosporidium parvum.

Diagnosis of Rotaviruses and Coronaviruses

An etiological diagnosis based solely on the clinical picture is not possible, as the clinical courses of these diarrhea-causing pathogens overlap and mixed infections are the norm. Antigen detection in fresh feces from several untreated calves that became ill early in the disease allows for the identification of the spectrum of pathogens and, consequently, targeted therapeutic, hygiene, and herd management measures.

Rapid Tests for Calf Diarrhea

The Fassisi® BoDia test family (BoDia, BoDia Plus, BoDia + Gia, BoDia MPX, Fassisi® BoDia Advanced MPX) detects rotavirus and bovine coronavirus antigens in calf feces. The combination and multiplex variants simultaneously detect other diarrhea-causing pathogens (E. coli K99/F5, Cryptosporidium parvum, and, depending on the variant, additionally Clostridium perfringens and Giardia duodenalis), which aids in the diagnosis of single and mixed infections from a single sample.

Evidence: Sources page.