Equine coronavirus was first identified in 2000 in foals with diarrhea. In recent years, the virus has been found in adult horses experiencing fever and gut-related issues.
In 2021, multiple horses in Switzerland fell ill with what has been confirmed as a new strain of equine coronavirus. The outbreak, which was detected under a voluntary surveillance program, was rapidly diagnosed and contained.
Dr. Melanie Hierweger and researchers from the University of Bern and the University of Zurich reported that 26 horses lived on the affected farm in the Canton of Bern.
The first horse became ill with a fever and severe respiratory disease; unable to have the issues resolved, the horse was euthanized. Six horses became ill in the following weeks, spiking a fever and losing appetite. Unlike the first horse, these six developed gut-related diseases, and some also had a low white blood cell count.
One horse showing signs of toxic shock was taken to the University of Bern with a fast heart rate, rapid breathing, increased capillary refill time, and congested mucus membranes. The horse died and was necropsied, and was found to have acute, severe necrotizing enterocolitis. Salmonella, clostridium infection and parasites were ruled out as the cause. A fecal sample was tested and confirmed to show equine coronavirus.
A second horse was admitted to the hospital because he was dull, with diarrhea and a poor appetite. The horse recovered with supportive care and was released after 10 days. This fecal sample was also positive for coronavirus.
Fecal samples were taken from all other horses on the farm. One of the horses with clinical signs and two others that were symptom-free were positive for the virus. The researchers believe that the first horse suffered from a disease that was not equine coronavirus.
Biosecurity measures were put in place and all horses on the farm had their temperatures taken daily to alert veterinarians of possible additional cases. None were discovered.
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Gene sequencing showed that the infections were all the same strain, which the scientists called Equine Coronavirus CH21. This infection is closely related to other equine coronavirus strains. Testing showed that prolonged viral shedding and subclinical infections occur, which may have implications for disease control measures.
Prior to these horses, no equine coronavirus outbreaks had been reported in Switzerland. The researchers say they found no evidence of equine coronavirus having the ability to pass from horses to humans.
Read the study here.
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