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Equine Coronavirus: An emerging virus in adult horses

Kaitlin A. Mielnicki

Equine Coronavirus was first discovered in Japan several years ago. The virus quickly spread to Europe, and testing in the U.S. for the virus began in 2010. Since then, the number of positive cases in the U.S. has been steadily increasing.

Effects of Equine Coronavirus

Equine Coronavirus is most commonly diagnosed in the winter months (October through April). Once exposed to the virus, it takes approximately 2 to 3 days for the infected horse to start showing clinical signs. One study showed, however, that only 30% of infected horses become visibly ill. Of the horses that are visibly ill, nearly all initially develop a fever. Sluggishness and dullness, lack of appetite and dehydration often follow. Rarely, ill horses will develop abdomen pain, gas and/or diarrhea.

These clinical signs may be present in horses of all ages, however, the disease is most commonly seen in older horses. It also has been suggested that ponies and miniature horses may be more severely affected by Equine Coronavirus infection, with illness progressing to endotoxemia (endotoxins in the blood), sepsis (inflammatory response to infection) and/or neurologic signs (head pressing, circling, incoordination, and seizures).

Diagnostic testing and disease life cycle

The easiest, most common diagnostic test is to submit a manure sample for fecal Polymerase Chain Reaction (PCR). PCR detects the presence of a virus in the feces. A veterinarian may run blood tests (complete blood count and chemistry profile), particularly if the horse has a fever or diarrhea. The results are used to evaluate the degree of infection and inflammation, electrolyte imbalance, and the health status of the kidneys and liver, which may be affected indirectly by Equine Coronavirus.

It should be noted that one study has shown that the number of viral organisms present in the horse’s feces may be directly related to the course of the horse’s disease. For example, horses with higher concentrations of viral organisms in the feces may have a decreased chance of survival. At this time, however, there is no easy or cost-effective way to measure fecal viral load in horses.

The disease itself may last a few days to a week or two, depending on the progression of the disease and response to therapy. Treatment of horses with Equine Coronavirus infections is supportive care and includes anti-inflammatory medications, oral and/or intravenous (IV) fluids (with or without electrolyte supplementation) and other therapies to prevent progression or complications of the disease.

Disease transmission

A horse can become infected if it comes into contact with the virus in contaminated fecal material present on tack, grooming equipment, boots, hands, and other shared items. Aerosolization or misting of the virus, through sneezing, for example, may also play a role in the transmission of the virus from horse to horse. Transmission of the virus is not fully understood, as horses that live with no known exposure to other horses, their manure or contamination items, may still develop the disease.

Equine Coronavirus is a newly recognized disease in horses in the U.S. As such, there is still much to learn about the disease, including the prevalence of the disease in our area, demonstrating the increasing need for diagnostic testing for the virus here in the Midwest.

For horses showing any of the mentioned signs, or for more information regarding this disease, please contact the University of Minnesota Equine Center at 612-625-6700.


Fielding CL, Higgins JK, Higgins JC, et al. Disease associated with Equine Coronavirus Infection and High Case Fatality Rate. J Vet Intern Med. 2015; 29:307-310.

Pusterla N, Vin R, Leutenegger C, et al. Equine coronavirus: An emerging enteric virus of adult horses. Equine Veterinary Education. 2016; 28:216-223.


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