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Neurologic Horses Euthanized in Arizona and California

Cases of potential neurologic equine herpesvirus were euthanized in Yavapai County in Arizona and Alameda County in California.
shavings horse head laying down

One mare that had non-neuropathogenic herpesvirus was at the St. George/Hurricane, Utah, Dixie Classic horse show at Washington County Legacy Horsepark.

Two horses in Arizona and one horse in California have been confirmed or suspected positive for equine herpesvirus. One horse in Maricopia County, Arizona, was ill with herpesvirus, but it did not have the neurologic form. The other two positive horses had neurologic signs and were euthanized.


The California Department of Food and Agriculture (CDFA) confirmed a case of equine herpesvirus myeloencephalopathy (EHM) in Alameda County on March 26. The horse was a 3-year-old Thoroughbred mare that had onset of severe neurologic signs on March 23. The vaccination status was not reported. The mare was euthanized.

One barn of exposed horses was placed under quarantine with enhanced biosecurity measures and twice-daily temperature monitoring. CDFA personnel were on-site and continue to monitor the situation.


The Arizona Department of Agriculture confirmed an 8-year-old Quarter Horse mare was positive for EHV-1. Her onset of clinical signs was March 21, and those signs included fever, tachycardia and limb edema. She was sent to a vet hospital and tested positive for non-neuropathogenic herpesvirus.

This mare had been at the St. George/Hurricane, Utah, Dixie Classic horse show at Washington County Legacy Horsepark.

In Yavapai County, Arizona, a horse with neurologic signs suspected to be EHM was euthanized. The onset of neurologic signs was March 22. Lab samples were collected and tests were pending.



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