Equine coronavirus (ECoV) infection is an emerging virus that has caused several outbreaks of pyrogenic and enteric disease in adult horses in the United States and Japan. It is characterized by onset of fever, lethargy/depression, and loss of appetite in affected horses.
Less than 20% of affected horses may also develop abdominal pain and changes in fecal character, ranging from soft-formed manure to acute, watery diarrhea. Other less frequent signs may develop in horses as a result of hyperammonemia, manifesting as severe depression, recumbency, proprioceptive deficits (abnormal body positions or movements due to a lack of normal perception), nystagmus (involuntary, rapid and repetitive movement of the eyes), seizures, ataxia, and head pressing. With supportive care (consisting of administration of anti-inflammatory drugs such as NSAIDs and oral or intravenous fluids for maintaining hydration), most horses affected by ECoV fully recover within 1-4 days. However, there have been incidences where horses develop septicemia, endotoxemia, or encephalopathy as a result of metabolic abnormalities in which the disease becomes fatal.
ECoV has historically been detected in horses through the use of electron microscopy, antigen-capture ELISA, or viral isolation from the feces. However, one problem with these available tests is that they lack sensitivity to properly and consistently detect the virus, especially if there are not many viral particles present in the sample. The quantitative polymerase chain reaction (qtPCR) assay has been found to be the most effective diagnostic tool for ECoV in horses.
ECoV can be shed from infected horses, into their feces and the environment, for up to two weeks following the horse's recovery from infection. Other horses can acquire ECoV from fecal-oral route.
ECoV has a short incubation period of 48 to 72 hours.
In 2011, 132 racehorses housed with a total of 600 horses in Japan developed ECoV. Five separate outbreaks occurred at boarding stables in the United States affecting 75 horses between 2011 and 2012.