Horsing boarding facilities on the coast are instituting a voluntary quarantine of horses after the first confirmed cases of a deadly form of the equine herpes virus in San Mateo County were recently identified.

Three stables in the Moss Beach and Montara area are under voluntary quarantine to help stop the spread of the neurotropic form on equine herpes virus. The San Mateo County Farm Bureau reported the outbreak Friday afternoon.

Three cases were identified at a boarding facility in Montara, north of Half Moon Bay on March 12. A 4-year-old horse became feverish March 6. She began showing slight signs of ataxia on the evening of March 11th, and was unable to stand the next morning. At that time, one other horse in the paddock was also ataxic, according to the statement of the farm bureau’s Web site.

A diagnosis of equine herpes virus was made based on history, clinical signs and the number of horses affected. The horse was referred to the University California at Davis Large Animal Clinic. The diagnosis was confirmed the afternoon of March 12 based on a positive nasal swab, blood and spinal tap. Two other horses at the boarding facility have also tested positive, with one other pending, according to the statement.

Two of the affected horses were subsequently euthanized at UC-Davis after failing to respond to treatment.

Equine herpes is a fairly common virus among horses. Humans cannot get the disease, but can inadvertently spread it among animals by touching them or using contaminated equipment. The virus is usually transmitted between horses through the air and through nasal secretions.

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