This post was updated on
photo © Bishop Mule Days Celebration
Two California horses confirmed positive for equine herpes myeloencephalopathy (EHM), a neurological disease caused by the equine herpes virus (EHV-1), have been euthanized. State ordered quarantines have been established in two counties.
The California Department of Food and Agriculture states there are a total of three confirmed cases of EHV-1 after attendees returned from the Bishop Mule Days Celebration. The event, located in Bishop, took place from May 17th through the 26th.
The department reports a 12-year-old Quarter Horse that attended the Bishop Mule Days Celebration spiked a fever of 106 degrees on May 30th. The horse, located in Riverside County, began exhibiting neurological signs days later.
A mule from the same farm also attended, but never had a fever, although it did have a cough. It has not shown any other clinical signs. Both the horse and mule are recovering.
An 8-year-old Quarter Horse that did not attend Mule Days was euthanized after becoming ill on June 4th. The roping horse, a stablemate of the two equids, exhibited a high fever and severe incoordination with his hind limbs. The gelding’s condition deteriorated leading to euthanasia on June 10th. CDFA officials confirm the Quarter Horse was diagnosed with EHM.
The Riverside County stable houses 19 horses and mules and is currently under a state-ordered quarantine.
A farm in San Joaquin County is also quarantined after a horse there was euthanized. A 13-year-old Quarter Horse mare was confirmed positive for equine herpes myeloencephalopathy (EHM). The mare didn’t attend the Mule Days in Bishop, but she was reportedly exposed by two mule stablemates that did. The mules are asymptomatic for EHV-1, according to state officials.
The Quarter Horse began exhibiting symptoms on June 5th including lethargy, fever, stocking up and severe incoordination of her hind limbs. The mare was euthanized on June 14th and tests confirm she was positive for the neuropathogenic strain of EHV-1.
The affected premises is home to 10 horses and mules. No other animals are reportedly affected.
Symptoms that should alert horse owners to the possibility of a neurologic EHV-1 infection include fever, weakness, incoordination, and urine dribbling or the inability to urinate. Horses with these symptoms should be examined immediately by a veterinarian.
Veterinarians recommend using proper biosecurity measures to help protect your horses from the potential spread of EHV-1 or any other illness.
EHM is the mutant form of EVH-1. There is no vaccine currently on the market that has a label for prevention of the neurologic form of the disease.
The last case of EHV-1 in the state was in March.