Researchers closer to unravelling the mysteries of equine coronavirus

The PCR Research and Diagnostics Core Facility at the UC Davis lab offers real-time diagnostic and research services.
The PCR Research and Diagnostics Core Facility at the UC Davis lab gives same-day results of ECoV testing.

The origins of equine coronavirus remain a question mark to veterinarians, but researchers at UC Davis are hopeful of someday finding the root cause.

In recent years, many commonalities have been found among horses infected with the disease, which is helping veterinarians better diagnose and treat the disease, as well as helping horse owners manage or even prevent an outbreak.

Signs of the disease include anorexia, lethargy, and fever, as well as mild colic-like signs.

Dr Nicola Pusterla with UC Davis veterinary students.
Dr Nicola Pusterla, who is at the forefront of equine coronavirus research, with UC Davis veterinary students.

Some suspect ECoV may have developed from bovine coronavirus and spread across species. What is known about the spread of ECoV among horses is that respiratory shedding of the disease is unlikely. ECoV is mostly spread feco-orally, according to Dr Nicola Pusterla, meaning it can be passed from horse-to-horse via exposure to contaminated feces.

Pusterla recently gathered all of the clinical equine veterinarians at UC Davis to update them on the disease. He reviewed several case studies to better prepare the clinicians for ECoV cases that may arrive at their Large Animal Clinic. The UC Davis veterinary hospital has several board-certified equine infectious disease specialists and technical staff experienced with treating the disease. Facilities include an isolation unit to treat the horses without infecting other hospitalized animals, as well as an on-site laboratory to immediately perform diagnostic tests to confirm the disease and develop an appropriate treatment plan.

The school’s research showed that most horses with ECoV will present as anorexic (98%) and lethargic (88%), with an elevated rectal temperature (≥ 101.5°F; 81%). Less common signs may include diarrhea (23%), colic (16%), and neurologic deficits (4%) such as aimless wondering, headpressing, recumbency or seizures. However, veterinarians should not assume that symptomatic horses have ECoV and asymptomatic horses do not. PCR (polymerase chain reaction) testing throughout Pusterla’s research confirmed that 10-20 percent of asymptomatic horses involved in outbreaks have detectable ECoV in their feces.

Currently, molecular detection of equine coronavirus in feces is the only diagnostic method available.
Currently, molecular detection of equine coronavirus in feces is the only diagnostic method available.

While ECoV was reported in foals more than two decades ago, ECoV in adult horses has only recently been recognized as a new infectious virus. Unfortunately, little research has been performed to better understand the virus and its disease. Dr Pusterla and his team are continuing to discover more of this emerging disease’s traits.

Initially, ECoV was associated only with foals, but outbreaks around the world among adult horses confirm that the disease is not age specific. In 2011, a group of adult draft racing horses in Japan contracted the disease, and groups of adult horses at facilities in more than ten US states were infected between 2011-14. With increased awareness of ECoV infection in horses and the availability of testing modalities, outbreaks of ECoV continue to be reported across North America.

UC Davis works with many of these facilities to help contain the outbreaks and treat the animals by offering diagnostic support in exchange of clinical and biological information on the infected horses. This data helps researchers further their understanding of ECoV and gain valuable epidemiological information.

The PCR lab at UC Davis can test for more than 80 infectious pathogens.
The PCR lab at UC Davis can test for more than 80 infectious pathogens. ECoV is a standalone test, and can also be done as part of a comprehensive Equine GI/Diarrhea Panel (ECoV, Lawsonia intracellularis, Potomac Horse Fever, Salmonella spp, and Clostridium difficile toxins A and B).

First and foremost, the mortality rate is low. Many horses may contract ECoV, but few will die from it. In a recent UC Davis study, only 8 percent of horses infected with ECoV died as a result of complications such as endotoxemia (endotoxins in the blood), sepsis or hyperammonemic encephalopathy (excess ammonia in the blood which damages the brain). Furthermore, the infection is generally short-lived. Clinical signs persist for only one to four days and are cleared with general supportive care.

Affected horses can shed the virus for up to 21 days without any obvious signs of illness.

Pusterla encourages horse facilities to continuously enforce biosecurity protocols to stop the spread of ECoV and take extra precautions at events where large groups of horses converge.

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