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Linda Mittel, MSPH, DVM and Erin Goodrich, DVM

 

For years, veterinarians have recognized equine coronavirus (ECoV) as a cause of intestinal disease in foals. Recently, however, gastrointestinal illness associated with ECoV has been seen in adult horses.

A number of coronaviruses cause both respiratory and gastrointestinal disease in humans and affect many species, including birds, dogs, cats, whales, cattle, camels and bats. Up to this point, ECoV has only been reported as a gastrointestinal disease without a respiratory component.

These species-specific viruses are classified as alpha, beta, gamma or delta. The betacoronavirus that affects cattle tends to cause both respiratory and gastrointestinal signs, predominately during the cold winter months, and is commonly referred to as winter dysentery. Similarly, veterinarians see ECoV, also a betacoronavirus, most often in the colder months of the year.

Infected horses tend to have fevers exceeding 102oF, lose their appetites and appear depressed and lethargic. Typically, these signs resolve in one to four days with minimal treatment. Less commonly, horses might experience one or two days of diarrhea or loose feces and signs of mild colic such as flank watching and lying down. In rare instances, other complications can occur, such as septicemia (bloodstream infection), endotoxemia (endotoxins from bacteria released in the bloodstream), and encephalopathy (a brain disorder). These complications are associated with coronavirus breaking down the intestinal tract barrier, which allows bacteria and their byproducts to enter the bloodstream. 

Researchers have not yet discovered the source of ECoV outbreaks. Horses on many farms where outbreaks have occurred have no history of travel or exposure to horses that don’t live on the farm or new arrivals. They do know ECoV spreads from horse to horse by fecal-oral transmission. Both clinically affected horses (showing signs of disease) as well as asymptomatic shedders (with no signs of disease but viral particles in their feces) can spread the virus to other horses. Scientists do not know if there are “carrier” animals that might serve to infect other horses. 

To diagnose coronavirus, veterinarians must submit a fecal sample for polymerase chain reaction (PCR) testing. This molecular test can detect the presence of the corona genomic RNA. During an ECoV outbreak, morbidity (clinical sickness) levels tend to be high, but mortality rates are quite low. This means many horses get sick when exposed to ECoV, but very few die as a result. Typically, treatment involves supportive care such as intravenous fluids; fever-reducing medications; and gastrointestinal protectants and anti-ulcer medications.

Due to the highly infectious nature of the coronavirus, whenever a veterinarian suspects or confirms cases on a farm, the property manager must institute appropriate biosecurity measures to minimize disease spread. Keep in mind that horses can shed the virus in their manure for several weeks following signs of illness, and some horses shed the virus without showing any signs at all. Encourage horse handlers to use disinfectant footbaths, individual thermometers for each horse, and disposable gloves if possible. Hand-washing is also important for preventing transmission. Isolate affected animals, and handle them last using separate equipment from what’s used in the rest of the barn. Also limit traffic into and out of the barn, use veterinary-grade disinfectants to inactivate the virus. Taking proper biosecurity measures each day will help not only protect your horse from ECoV but also prevent infectious disease outbreaks of all sorts.

 

About the Author:

Linda Mittel, MSPH, DVM is a senior extension associate in the Department of Population Medicine and Diagnostic Sciences, and Erin Goodrich, DVM, is a veterinary support specialist, both conducting research at Cornell University’s Animal Health Diagnostic Center in Ithaca, New York.

 

This article is provided courtesy of AAEP Media Partner, The Horse.