Bovine coronavirus is one of the most common causes of diarrhea in young calves.
A Kansas State database suggests that one in three cases of diarrhea in calves between one and nine weeks of age may be caused by bovine coronavirus.
The virus causes a profuse watery diarrhea in young calves, usually between five and 15 days of age.
Coronavirus invades the lining of the intestinal wall of the calf and causes severe damage to the microscopic finger-like projections on the lining of the bowel. This decreases the intestine’s ability to absorb nutrients and fluid and leads to a severe diarrhea.
Read Also
Canada’s simplified BSE testing program shows good uptake
Going by the number of submitted material samples so far, cattle producers’ response so far to an updated national surveillance program for BSE is encouraging for Canada’s CFIA.
Coronaviruses are particularly damaging because they can attack both the small and large intestine simultaneously.
The diarrhea may contain mucus or blood at the beginning but progresses to a severe watery diarrhea. The result is a rapid loss of water and electrolytes such as sodium, potassium and bicarbonate. Affected calves can rapidly become dehydrated and have severe electrolyte imbalances.
Calves become depressed and weak as they become clinically dehydrated, and their temperature often drops. If left untreated, they may progress to a coma-like state and die.
The viral damage to the intestinal wall can be so severe that oral electrolytes will not be absorbed properly and the calf often requires intravenous fluid therapy to restore the fluid and electrolyte balance. These calves can survive if treated with intravenous fluids by a veterinarian but may continue to die if producers rely only on oral electrolytes.
We have also seen outbreaks of coronavirus intestinal infections in calves that don’t cause severe diarrhea but damage the bowel enough to create severe electrolyte disturbances, which severely drop the pH of the blood. These infections produce calves that may continue to attempt to suckle but suddenly appear weak, disoriented and have difficulty standing, walking and suckling.
The electrolyte disturbances in these calves can be quickly corrected with the use of the appropriate intravenous fluids by a veterinarian. Oral electrolytes might also be beneficial in these cases.
The source of the infection is from cows that do not show clinical evidence of disease but shed the virus in their feces.
Bovine coronavirus is widespread in the cattle population and persists in many adult cows.
Many of our management strategies for preventing coronavirus diarrhea involve reducing the exposure of young calves to the manure of adult cows:
- Winter cows on a separate wintering area and then moving them to a clean calving area.
- Spread out cow-calf pairs.
- Providing creep areas or shelters to calves or by using methods such as the Sandhills Calving method or the Lacombe Calving method, which try to ensure calves are born on uncontaminated ground.
Calves that have clinical disease shed extremely high levels of virus and so it is important to isolate any clinical cases from the rest of the herd.
Commercial vaccines are also available to help prevent coronavirus diarrhea in young calves. These scours vaccines often contain E. coli, rotavirus and coronavirus and are given to the cow before calving to increase the levels of antibodies in the colostrum and the milk.
Adequate colostrum intake is also important.
Bovine coronavirus can also invade the lining of the respiratory tract, and there is increasing evidence that coronavirus may be an important cause of respiratory disease outbreaks in calves and feedlot cattle.
Researchers are still debating if the virus strains isolated from the respiratory tract are identical to those isolated from the intestine, but several studies have demonstrated that coronavirus may be a possible cause of respiratory disease in young calves.
Some studies have shown calves can simultaneously shed bovine coronavirus from nasal secretions and the gastrointestinal tract.
Winter dysentry is another syndrome linked to bovine coronavirus.
It is more commonly seen in housed adult cattle such as dairy animals and occurs as an explosive outbreak of diarrhea affecting at least 15 percent or more of the herd. The diarrhea will often last a few days, and most animals will recover without treatment. As the name suggests, we most commonly see outbreaks of this disease during winter.
