Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Coronavirus Entero-Colitis

Synonyms: ECoV, Winter Dysentery


Historically, coronavirus was considered a rare cause of foal diarrhea. It had not been considered a disease that affected adult horses. PCR tests have provided improved methods of detection and, in 2011, this condition was found in stabled adult horses that had colitis. Since then, coronavirus is diagnosed more frequently. Dr. Nicola Pusterla (UC Davis) is on the forefront of research on this condition.

Affected horses usually have a fever, are depressed and have a poor appetite. Manure varies from normal to soft "cowpie", to diarrhea. Occasionally signs of abdominal pain (colic) are present. As of 2013, I have treated several outbreaks in which we have detected this organism.

Coronavirus is probably spread through contact with manure that contains the virus via human handlers and shared equipment.

This disease is fairly mild and self-limiting, meaning that it usually resolves on its own in time. The cases I have treated responded to supportive care, NSAID's for fever, and fluid therapy, if necessary. In my experience, this condition is much milder than the bacterial colitis cases that we more commonly see.

my vet's role



Other conditions or ailments that might also need to be ruled out by a vet.

Very Common
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The prognosis is good in most cases. In rare cases, severe endotoxemia and shock can develop. Horses are typically ill for 1-4 days. They may shed the virus for up to 14 days after the first signs.

my role


I might observe

You might make these observations when a horse has this condition.

Very Common
Less Common
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Questions To Ask Your Vet:
  • How is this diagnosis reached?
  • How reliable is the testing?
  • Are my other horses at risk?
  • What is the best method of controlling spread to my other horses?

All of the factors that go into reducing risk for transmissible diseases should decrease the likelihood of this disease, including quarantine of new horses in a facility.

Horses that have had disease may shed the virus for 14 days, so they need to be quarantined at least this long following illness to prevent transmission to other horses.

Currently, there is no vaccine available.

further reading & resources

Related References:

Worms & Germs Blog. Weese S. Equine Coronavirus: A New Problem? Available at: http://www.wormsandgermsblog.com/2012/10/articles/animals/horses-1/equine-coronarvirusa-new-problem/. Accessed 2013.

Author: Doug Thal DVM Dipl. ABVP