CASE REPORT: Beta coronavirus outbreak on a horse breeding farm

Beta coronaviruses (BCoV) are often associated with gastrointestinal diseases in young horses but there have also been reports of outbreaks in adult horses in racing and boarding stables. To the author’s knowledge, this is the largest BCoV outbreak reported in a single, closed herd situation.

The index cases were two three-year old mares with fever, lethargy and mild colic signs. These symptoms were then seen in three further horses, ranging in age from six months to 12 years. In four out of the five cases, clinical manifestations were resolved in two-five days following the administration of nonsteroidal anti-inflammatory drugs and flunixin meglumine.

One of the index cases was still showing symptoms after five days so was referred for more intensive care. A PCR testing confirmed the presence of BCoV so faecal samples were collected from the remaining animals at the farm (28 horses and one donkey). From 30 animals of the farm, 25 tested positive for BCoV but only five (20%) were symptomatic. All of the negative results related to apparently healthy animals.

In this outbreak all of the infected animals recovered (0% mortality) and morbidity was low. A possible explanation may be the presence of foals as ECoV (equine enteric coronavirus, a beta coronavirus) is a common agent in healthy young foals and it is hypothesized that its discharge through foals´ faeces may have a protective effect on adult horses.

This report highlights the importance of testing all at-risk individuals and of defining quarantine timeframes for BCoV as the virus may be shed by animals both with and without clinical signs.

E.L. Goodrich et al. Novel findings from a beta coronavirus outbreak on an American Miniature Horse breeding farm in upstate New York. Equine vet. Educ. (2020) 32 (3) 150-154. doi: 10.1111/eve.12938