A statement on the California Department of Food and Agriculture (CDFA) website has confirmed four additional cases of neurologic equine herpesvirus-1 (EHV-1) on the index premises and one case on a premises in another county. The CDFA does not believe the two situations are related, the statement said.

On Jan. 24, four more horses on the Orange County premises tested positive, bringing the total number of confirmed cases on that farm to 15. Only one horse–the index case–has displayed neurologic signs and is reportedly recovering, the statement indicated. One horse was euthanized on Jan. 18 after becoming recumbent, however a necropsy led veterinarians to believe the recumbency was unrelated to the EHV-1, the report said.

Also on Jan. 24, a horse on a Riverside County farm tested positive for the neurologic form of EHV-1, the statement read. The horse reportedly exhibited hind limb incoordination and urine dribbling, became recumbent, and was subsequently euthanized.

"The premises is under quarantine and CDFA has initiated an epidemiologic investigation," the statement said. "At this time we are not aware of any links to the Orange County incident. Additional information will be posted as it becomes available