Four horses in Oregon confirmed positive for EHV-1

Equine herpes virus.
Equine herpes virus.

Four horses in Oregon have tested positive for Equine Herpes Virus-1 (EHV-1), with two of the horses showing neurological signs.

The first case, in a horse in Marion County stabled with about 20 other horses, was confirmed by testing on April 3. The animal was admitted to Oregon State University’s College of Veterinary Medicine’s Large Animal Hospital with neurological disease.

Subsequent testing has since confirmed three further cases, the Oregon Department of Agriculture said.

The second horse that developed neurological signs lived at a stable in Polk County with about 40 other horses.

It was taken to the Large Animal Hospital over the weekend.

The Polk County stable has been placed under quarantine and the remaining horses are being monitored by the stable manager and a veterinarian.

In addition to the Polk County stable, two Marion County farms remain under quarantine due to exposure to EHV-1.

The infected horses and other horses exposed at the quarantined facilities attended an Oregon High School Equestrian Team event at the Linn County Fairgrounds on April 16-19.

State agriculture officials are currently investigating the potential of any additional exposures at this time. They are working to notify owners of horses whose animals have been potentially exposed and have notified Oregon equine veterinarians.

The EHV-1 virus is widespread in the equine population, usually causing respiratory systems and sometimes abortion in mares. However, it is capable of causing more serious disease, including neurological effects. One particular strain of EHV-1 is more likely to cause neurological disease.

The most common way for EHV-1 to spread is by direct horse-to-horse contact. The virus can also spread through contaminated equipment, clothing, and hands. Signs include fever, decreased coordination, nasal discharge, urine dribbling, loss of tail tone, hind limb weakness, leaning against a wall or fence to maintain balance, lethargy, and the inability to rise.

While there is no cure, the clinical signs of the disease may be treatable.

State veterinarian Dr Brad LeaMaster urged horse owners to practice strict biosecurity measures and hygiene when going to shows and competitions with their animals.

“The detection of neurologic EHV-1 is taken very seriously and we are doing our best to notify equine veterinarians and horse owners,” LeaMaster said.

“We have had occurrences of the disease in Oregon in the past. I appreciate everyone’s cooperation in dealing with the disease investigation and control process.”

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