Four horses have tested positive for a non-neurologic strain of equine herpesvirus-1 (EHV-1), according a March 29 statement from the Snohomish, Wash.-based Pilchuck Veterinary Hospital. The statement cites the Washington State Veterinarian as the source of information.

According to the statement, the four EHV-1 positive horses are from two separate facilities, both of which are under voluntary quarantine. Potentially exposed horses at both facilities are being monitored closely for signs of disease, the statement said.

The statement noted that three of the four affected horses attended the HITS Thermal Horse Show March 5-11, 2012, in Thermal, Calif., that also saw three California horses sickened. The fourth horse is being considered a "secondary exposure," the statement said.

No further information regarding the horses’ conditions was immediately available. Phone calls to the Washington State Veterinarian’s office seeking further information on the confirmed cases have not yet been returned, as of press time (1:30 p.m. EDT)