Equine Coronavirus (ECoV) is a highly contagious illness transmitted between horses that can cause fever, anorexia, diarrhea, and colic. [1][2][3]

Most horses recover from equine coronavirus with supportive care. In serious cases, affected horses may require specific treatments such as electrolytes, fluid administration, and anti-inflammatory and antibiotic medications.

Death from the illness is uncommon and believed to be secondary to complications associated with gastrointestinal barrier disruption. [1]

There is no vaccine for equine coronavirus. Proper biosecurity practices at your barn can significantly reduce the risk of horses contracting the illness. [1]

Strategies to prevent the transmission of coronavirus in horses include quarantining sick horses, practicing good hygiene in equine facilities, and monitoring horses for signs of illness. [1]

What is Equine Coronavirus?

Equine coronavirus is a member of the Coronaviridae family of viruses which infects amphibians, birds, and mammals. This family of viruses is responsible for causing disease in the gastrointestinal, respiratory, liver, and neurological systems. [1]

Viruses within the Coronaviridae family are called RNA viruses as they have ribonucleic acid (RNA) as their genetic material. [1]

The Coronaviridae family of viruses is comprised of alpha, beta, gamma, and delta coronaviruses. The equine coronavirus is a beta coronavirus.

Genetically, equine coronavirus and bovine coronavirus are related. Equine and bovine coronaviruses are not infectious to humans. [1]

Equine coronavirus can affect horses of all ages and breeds. The virus is transmitted through the fecal-oral route (oral ingestion of feces) contaminated with the virus. [1]

A diagnosis of ECoV is based on clinical symptoms and laboratory testing. The qPCR test is used to make a definitive diagnosis of the illness. [1]

Clinical signs of ECoV typically occur two to three days after exposure to the virus. Not all horses with equine coronavirus display clinical signs; some are asymptomatic carriers of the virus. [1]

Prevalence

Outbreaks of equine coronavirus have been reported in horses located in the USA, Europe, and Japan. [1][4][5][6][7] Cases are known to occur sporadically and as a part of outbreaks. [1]

Outbreaks have been reported more frequently in horses used for riding, racing, and showing compared to horses used for breeding. [1]

According to three American veterinary diagnostic laboratories, reports of the illness have increased since 2010 when the quantitative polymerase chain reaction (qPCR) test came into use at molecular diagnostic laboratories. [1]

How is Equine Coronavirus Transmitted?

Equine coronavirus is believed to be transmitted through the feces of infected horses. Horses become infected with the virus when they ingest feces contaminated with the virus. [1]

In research experiments in the laboratory setting, ECoV has also been transmitted via a naso-esophageal route. [1]

Incubation Period

Once the virus enters the body, it has a short incubation period. Clinical signs of the condition develop between 48 and 72 hours after either natural exposure to the virus or experimentally-induced infection. [1]

Viral Shedding

Infected horses begin shedding the virus in their feces three to four days after exposure. Peak shedding typically occurs three to four days following the development of clinical signs. [1]

Horses that naturally contracted the virus can shed it in their feces for up to 25 days. Those with experimentally induced infection can shed the virus in their feces for 10 to 12 days. [8]

It is unknown how long equine coronavirus can remain in the environment and cause infection. [1]

Although ECoV can occur year-round, the illness is most frequently reported during the cooler months of October to April.

Researchers believe the virus may replicate more quickly in colder temperatures thus resulting in an increased number of cases occurring during the colder months of the year. [1]

Because shedding occurs two to three days after clinical signs develop, some horses may test negative for the virus during the very early stages of clinical disease. [1]

Effects of Equine Coronavirus

Equine coronavirus typically occurs as a single infection (monoinfection) in adult horses older than two years of age. [9] Foals with ECoV and clinical signs of the virus are more likely to have co-infections than adult horses.

One study found that all ECoV infections in foals with gastrointestinal disease were associated with coinfections, while most healthy foals infected with the virus had no other types of infections. [1][10]

A research study on foals in central Kentucky found that equine coronavirus shedding occurred in healthy subjects and those with gastrointestinal disease. This research suggests that the virus can circulate among foals that have no clinical signs of the illness. [10]

Signs & Symptoms

Between 10 and 80% of horses infected with equine coronavirus will show signs of the disease. [1]

Some infected horses do not exhibit any clinical signs of the virus (they are asymptomatic). They still carry and can transmit the virus to other horses through their feces. [11]

Signs of coronavirus in horses typically last between a few days and a week. [1] Common clinical signs include:

  • Anorexia
  • Depression
  • Fever
  • Diarrhea
  • Colic
  • Nasal secretions

Laboratory findings associated with ECoV include: [1]

  • Abnormalities in white blood cell count
  • Changes in electrolyte concentrations if the intestinal illness is present
  • Elevated bilirubin levels due to weight loss causing anorexia

According to data collected during 16 outbreaks that occurred between 2011 and 2014, 30% of 406 horses showed clinical signs of the ECoV: [1]

  • The most common signs of the illness included weight loss (98%), lethargy (89%), and fever (84%).
  • Horses with fever due to ECoV had rectal temperatures ranging from 38.6 to 41oC or 101.4 to 105.8oF
  • 18% of affected horses had changes in the consistency of their feces.

The percentage of asymptomatic horses during an outbreak of ECoV has been observed to range between 11 and 83%. [12]

Complications

In rare cases of equine coronavirus, normal brain function can be impaired (encephalopathy) due to high levels of ammonia (hyperammonaemia) in the blood.

Encephalopathy can occur as a complication of coronavirus in horses due to increased ammonia production by bacterial overgrowth in the intestines or from increased ammonia absorption through a damaged intestinal mucosal barrier. [1][13]

Horses with this complication may exhibit:

  • Circling
  • Head pressing
  • Poor muscle coordination
  • Involuntary eye movement
  • Lying down more frequently
  • Seizure

Diagnosis

Contact your veterinarian as soon as possible if you notice your horse is not acting or feeling normal. Diagnosis of this condition based on clinical signs and laboratory testing.

A veterinarian can determine if your horse has equine coronavirus and rule out other conditions that can cause intestinal and respiratory signs. For example, various respiratory illnesses cause nasal secretions that are not associated with ECoV.

The prevalence of equine coronavirus in the nasal secretions of horses with fever and respiratory disease is low. [14] A study of 2,437 horses with fever and signs of respiratory disease found that ECoV was detected in less than 1% of samples of nasal secretions. [14]

Horses that present with clinical signs including sudden onset of fever, lethargy, and anorexia, but do not have any respiratory signs, should have their feces tested for ECoV. [1]

Fecal Samples for PCR testing

Equine coronavirus can be detected in fecal samples from infected horses using the quantitative polymerase chain reaction (qPCR) test.

According to research conducted on populations of horses with virus outbreaks, the qPCR test has an accuracy rate of 90% or greater. [1][12]

The fecal sample used for testing should be collected fresh and stored in a leak-proof container or bag. [16] Samples must be kept cold or frozen to prevent excessive bacterial growth that can interfere with PCR testing.

Prognosis

The prognosis for horses diagnosed with equine coronavirus is good and most horses recover fully and without complications. [1] Clinical signs of ECoV typically resolve with minimal supportive care.

The amount of ECoV in the bloodstream (viral load) of infected horses influences clinical outcomes and mortality rates. [1][15] This is affected by the specific strain of coronavirus-causing infection that the horse has contracted.

Equine coronavirus has a low mortality rate. If death due to ECoV occurs, it is typically associated with a secondary illness involving: [1]

  • Systemic inflammation caused by decreased gut barrier function (endotoxemia)
  • The body’s injuring its own tissues and organs in response to the infection (septicemia)
  • Damage to the brain (encephalopathy)

A small study of 14 miniature horses found this breed had an increased rate of mortality from equine coronavius compared to the case fatality rates previously reported in outbreaks among other breeds. [16]

Treatment

There are currently no antiviral drug treatments or vaccines available for equine coronavirus. [1]

Most adult horses with clinical signs of ECoV infection recover without specific treatment over a period of a few days or longer. [1]

Horses with persistent clinical signs may require medication delivered orally, intravenously, or via nasogastric intubation. More severe cases may require extensive treatment or hospitalization.

Potential treatments for coronavirus in horses include: [1]

Anti-inflammatory Drugs

Horses with ECoV infection and a consistently elevated rectal temperature, anorexia, and depression may be treated with nonsteroidal anti-inflammatory drugs such as Banamine (flunixin meglumine) or Bute (phenylbutazone).

Fluid and Electrolytes

Horses with colic, anorexia, and/or diarrhea may require oral or intravenous fluid and electrolyte administration until their hydration and electrolyte levels normalize and their clinical signs resolve.

Antimicrobials

Antimicrobial medications may be used to treat horses that are developing signs of advanced systemic infection due to disruption of their gastrointestinal barrier.

Gastrointestinal Protectants

Probiotics and other gastroprotective agents may be beneficial to help repair a damaged gastrointestinal barrier in affected horses.

Fecal Transfaunation

Horses with equine coronavirus and hyperammonaemia may be treated with fecal transfaunation (the transfer of bacteria from the intestinal tract of a healthy subject to another subject) to restore their intestinal flora.

Horses with hyperammonaemia may also require additional treatments including antibiotics and laxative agents such as lactulose.

Prevention

The best method to prevent equine coronavirus is to keep your horse’s facilities as clean as possible.

Management practices to reduce the transmission of this illness at equine facilities include: [1]

Quarantining Ill Horses

Because equine coronavirus is highly contagious, any horse that develops clinical signs of illness should be isolated until a diagnosis is confirmed.

Signs to look out for include fever, loss of appetite, and depression with or without additional signs of colic or diarrhea.

Post-infection Testing

Horses recovering from ECoV should be tested to determine when they are no longer shedding the virus in their feces.

Until they stop shedding the virus, they should be kept away from other horses to prevent spreading the virus.

Assessing Clinical Signs

Horses that are suspected to have been exposed to equine coronavirus should be checked twice daily for clinical signs of disease. Take a rectal temperature to determine if viral infection is be present.

Using Footbaths

Footbaths should be used to sanitize footwear before moving from an area where an infected horse is being housed to other areas of an equine facility.

Practicing Good Hygiene

Horse handlers and riders should thoroughly disinfect their boots, tack, and hands after contact with horses infected with equine coronavirus.

Infected horses should be handled last when feeding, grooming, and cleaning stalls to prevent possible transmission of infection to other horses.

Disinfecting Trailers and Stalls

All vehicles used for horse transport should be thoroughly cleaned and disinfected after use. Stalls that house ill horses should be disinfected before another horse uses the stall.

Equine coronavirus is destroyed by common disinfectants including sodium hypochlorite, povidone-iodine, chlorhexidine gluconate, phenols, quaternary ammonium compounds, hydrogen peroxide, and peroxygen compounds.

Careful Manure Handling

Because the manure of infected horses is contaminated, it should be disposed of carefully. Any tools or equipment that contacts the contaminated manure should be disinfected to prevent the spreading of the virus.

Manure should be disposed of so it cannot contaminate pasture, paddocks, or drinking water.

Using Separate Equipment

Grooming tools, tack, bedding, and feed bowls used for horses with equine coronavirus should not be used for other horses unless the equipment has been thoroughly cleaned and disinfected.

Consult with your veterinarian and carefully practice the above strategies if you suspect one or more of your horses may have equine coronavirus. With proper care and management most horses recover fully and without complications.

If your horse has lost significant weight during the illness, consult with an equine nutritionist to formulate a diet plan to get them back on track.

Is Your Horse's Diet Missing Anything?

Identify gaps in your horse's nutrition program to optimize their well-being.

References

  1. Pusterla, N. et al. Equine coronavirus: An emerging enteric virus of adult horses. Equine Vet Educ. 2016.
  2. Schaefer, E et al. Investigation of an experimental infection model of equine coronavirus in adult horses. J Vet Intern Med. 2018.
  3. Mattei, DN. et al. Equine Coronavirus-Associated Colitis in Horses: A Retrospective Study. J Equine Vet Sci. 2020.
  4. Miszczak, F. et al. First detection of equine coronavirus (ECoV) in Europe. Vet. Microbiol. 2014.
  5. Nemoto, M. et al. Experimental inoculation of equine coronavirus into Japanese draft horses. Virol. 2014.
  6. Oue, Y. et al. Isolation of an equine coronavirus from adult horses with pyrogenic and enteric disease and its antigenic and genomic characterization in comparison with the NC99 strain. Microbiol. 2011.
  7. Oue, Y. et al. Epidemic of equine coronavirus at Obihiro Racecourse, Hokkaido, Japan in 2012. J Vet Med Sci. 2013.
  8. Pusterla N, Vin R, Leutenegger CM, Mittel LD, Divers TJ. Enteric coronavirus infection in adult horses. Vet J. 2018.
  9. Equine enteric coronavirus. Cornell University College of Veterinary Medicine. 2016.
  10. Slovis, N.M. et al. Infectious agents associated with diarrhoea in neonatal foals in central Kentucky: a comprehensive molecular study. Equine Vet. J. 2014.
  11. Kambayashi, Y. et al. Outbreak of equine coronavirus infection among riding horses in Tokyo, Japan. Comp Immunol Microbiol Infect Dis. 2021.
  12. Pusterla, N. et al. Emerging outbreaks associated with equine coronavirus in adult horses. Microbiol. 2013.
  13. Giannitti, F. et al. Necrotizing enteritis and hyperammonemic encephalopathy associated with equine coronavirus infection in equids. Pathol. 2015.
  14. Pusterla, N et al. Prevalence of equine coronavirus in nasal secretions from horses with fever and upper respiratory tract infection. Veterinary Record. 2015.
  15. Chen, W. et al. Nasopharyngeal shedding of severe acute respiratory syndrome-associated coronavirus is associated with genetic polymorphisms. Clin Infect Dis. 2008.
  16. Fielding, C.L. et al. Disease associated with equine coronavirus infection and high case fatality rate. J Vet Intern Med. 2015.