EHV-1 California Outbreak Increases to 11 Confirmed Cases

Two more cases of equine herpesvirus-1 (EHV-1) have been confirmed today, with the two horses displaying a fever. This is in addition to the one case announced yesterday by the California Department of Food and Agriculture (CDFA). The necropsy results from the positive horse euthanized Jan. 18 are still pending, and all horses on the Orange County, Calif., property continue to be monitored.

On Jan. 11 a gelding residing on a "large multidiscipline facility with no movement of horses on or off the property" tested positive for the debilitating virus. He was quarantined on the farm and is receiving veterinary care.

On Jan. 12 testing confirmed that two additional horses on the property were EHV-1-positive. Those horses were also isolated and quarantined on the same farm and are receiving veterinary attention. On Jan. 13, two additional horses on the premises tested positive for the virus, and on Jan. 18, three additional cases were reported.

While only one horse has displayed neurologic signs, the CDFA has indicated that all affected horses have been quarantined on the property and are receiving veterinary attention.

"All exposed horses on the property are being monitored, and enhanced biosecurity measures have been implemented," the statement read. "The source of the outbreak has not been identified."

Although it's not transmissible to humans, EHV-1 is highly contagious among horses and camelids, and it is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions. The disease can cause a variety of ailments in equines, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (EHM, the neurologic form).

Myeloencephalopathy is characterized by fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. Should a horse with potential EHV-1 exposure display any of the aforementioned clinical signs, a veterinarian should be called to obtain samples and test for the disease. will continue to provide updated information as it becomes available.

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