Wednesday, April 24, 2019

Protect horses from herpes virus

Dr. Amber Itle
Washington State Veterinarian

Vaccination, close monitoring and biosecurity can help
keep your horse safe from EHV. 
Equine Herpes Virus (EHV) is an emerging, potentially fatal animal disease in the United States.

It not only has the potential to affect horse health but, because it's highly contagious and requires lengthy quarantines or cancellations of events like rodeos and fairs, the economic consequences can be equally devastating.

As we enter the time of year when horses are more active and travel to public events, it's especially important to observe appropriate biosecurity measures, vaccinate, and watch for signs of the disease.

A case in Washington

Just this month, a horse in Thurston County tested positive for equine herpes virus 1, resulting in a quarantine of the boarding facility where it was kept.

The 19-year-old Gelding Warmblood had developed ataxia and loss of tail tone. It was taken to the referral center in Oregon and diagnosed on April 19.

The horse will remain in isolation at the referral center until a plan for moving it to an isolated facility can be determined. WSDA quarantined the boarding stable where the horse was housed prior to laboratory diagnosis. The quarantine will last until 14 days after WSDA confirms no more signs of the disease.

The horse will remain in quarantine until two negative PCR tests can be verified. The facility has cooperated fully with the quarantine order and is working to ensure strict biosecurity measures are in place.

This equine herpes virus 1 or “wildtype” strain of horse herpes tends to be less contagious than the “neuropathogenic” type.  However, both strains can cause neurologic signs that cannot be differentiated without diagnostic samples.

Equine herpes comes in three forms;  respiratory, abortion, and neurologic. Neurologic is of most concern because it is potentially fatal to the animal.

Unfortunately, many owners don’t understand that both the non-neuropathic strain (wildtype or A Strain) and neuropathic strain (G Strain) can cause equine herpesvirus myeloencephalopathy (EHM).

This neurological disease presents itself as a result of damage to blood vessels in the brain and spinal cord associated with herpes infection. Interference with the blood supply leads to tissue damage and a subsequent loss in normal function of areas in the brain and spinal cord.

If the horse has neurologic signs and a positive test, we consider it as a case of EHM.

What to watch for 

Given the infectious nature of EHV-1, WSDA asks horse owners to follow these recommendations.

Watch your horse for signs of possible infection including:
  • Fever of 101.5 F or higher.
  • Discharge from the eyes or nose.
  • Respiratory symptoms.
  • Swelling of the limbs.
  • Spontaneous abortions.
  • Neurological signs such as unsteady gait, weakness, urine dripping, lack of tail tone and recumbency.
Check your horse’s temperature twice daily, ideally first thing in the morning and last thing at night. Also, check before administering medications since some can lower body temperature.

Notify your veterinarian immediately if you detect any of the symptoms above. Your veterinarian may want to take nasal swabs for virus detection or blood samples for evidence of exposure to EHV-1.

When the virus is detected, WSDA and local veterinarians work closely with affected communities to ensure the best biosecurity standards are practiced. For more tips on keeping your own horses safe through good biosecurity practices, please see our previous blog post.

The time between exposure and illness from EHV-1 varies from two to 10 days. By self-quarantining animals with possible symptoms, practicing good biosecurity and contacting your veterinarian as soon as you suspect possible symptoms, you can help prevent the spread of this virus.

For more information, contact WSDA's Animal Health Program.