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.

Update on current equine herpes quarantine

Dr. Brian Joseph
Washington State Veterinarian

Interest has been high in a case of EHV-1, neuropathogenic strain, detected earlier this month in King County. This particular strain of equine herpes virus is highly contagious and, while it won’t infect people, it can be fatal to horses.

Since being notified of the infected horse on Dec. 13, WSDA has had a quarantine in place at the stable where it was housed. So far, 32 horses housed at the stable have been tested. The virus has been detected in 9 of these horses. Seven horses have been euthanized, while several others are being monitored.

The virus spreads between horses only at certain stages of the disease, so not all horses have currently been tested. Even though we may not detect the virus when testing, the horse may still be infected. At the same time, even if we detect the presence of the virus in the horse or if the horse develops neurological symptoms, it does not mean the horse will be euthanized. Most horses recover.

Given the highly infectious nature of the virus, we continue to urge horse owners to watch for signs of possible infection, such as:

• Fever of 102.5F 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.

We recommend that horse owners:

• Check your horse’s temperature twice daily, ideally first thing in the morning, and last thing at night. Also, check before administering medications as some can lower body temperature.
• Notify your veterinarian immediately if you detect any of the symptoms above.

In addition to working with the horses, WSDA and local veterinarians have been working closely with the local community to ensure excellent biosecurity is practiced whenever someone must leave the stable. For more tips on keeping your own horses safe through good biosecurity practices, please see our previous blog post on this incident.

The time between exposure and illness from EHV-1 varies from two to 14 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.

Tips for horse owners – protecting your animal from Equine Herpesvirus

Dr. Scott Haskell
Assistant State Veterinarian

Late last week, the Department of Agriculture was notified of one laboratory-verified case of Equine Herpesvirus Myeloencephalopathy, or EHV-1 wildtype, in Washington.

EHV-1 is a highly contagious virus that can be fatal to horses. The disease is spread from horse to horse through direct contact, on feed, tack and equipment. While people are not made sick by the virus, they can carry the virus on their clothes or hands. Horse owners should carefully wash their hands and equipment to prevent the spread of the virus.

WSDA is not currently establishing any quarantine, but our field veterinarians are actively tracing all areas where the infected horse might have contacted other animals.

Given the high risk of contamination, here are additional recommendations for horse owners.

Watch for symptoms
Closely observe your horse and look for signs of possible infection, which include:

• Fever of 102.5 degrees F or higher
• Discharge from eyes or nose
• Limb edema or swelling
• Spontaneous abortions
• Neurologic signs such as an unsteady gait, weakness, urine dribbling, lack of tail tone and recumbency.

Be sure to obtain and record the body temperatures of all horses on the premises twice a day, ideally first thing in the morning and last thing at night, and always before administering medications since some can decrease body temperature.

Let your veterinarian know if you detect a fever or notice any of the other symptoms listed. The veterinarian may want to take nasal swabs or blood samples to test for EHV-1.

EHV-1 testing at WSU
Suspected cases should be checked for both West Nile Virus and EHV1 by a veterinarian.  The Washington Animal Disease Diagnostic Laboratory in Pullman is providing testing.

Veterinarians should contact WADDL at 509-335-9696 to submit a red top and lavender top tube with nasal swabs directly to Dr. Jim Everman or Dr. Kevin Snekvik at WADDL.

Vaccines
It’s not too late to vaccinate your horse against EHV and there are a number of vaccines available.

Several EHV-1 vaccines available in North America carry a label claim for the control of respiratory disease induced by EHV-1 and EHV-4. These are multi-component inactivated vaccines specifically, Prestige® (Merck), Calvenza® (Boehringer Ingelheim Vetmedica) and Fluvac Innovator® (Zoetis) and the modified live vaccine Rhinomune® (Boehringer Ingelheim Vetmedica).

There are also two EHV-1 vaccines licensed for the control of abortion and respiratory disease. These vaccines are single-component inactivated vaccines, namely Pneumabort-K® (Zoetis) and Prodigy® (Merck).

Biosecurity – steps to protect your horse and others
To protect your horse from becoming infected, and help limit the potential spread of this virus, there are several things all horse owners should be doing.

1. Monitor all horses on your premises.
2. Limit direct horse-to-horse contact.
3. Limit stress to horses.
4. Don’t share equipment.
5. Clean barn areas, stables, trailers, or other equine contact surfaces thoroughly, removing all organic matter (dirt, nasal secretions, uneaten feed, manure, etc.) before applying a disinfectant. Organic material decreases the effectiveness of any disinfectant, especially if 10% bleach is used.
6. Use footwear disinfectant and hand sanitizer where indicated.
7. If you have a potentially exposed horse, restrict human, pet and vehicle traffic from the area where the exposed horse is stabled.
8. Clean all shared equipment and shared areas, again removing dirt and manure before application of a disinfectant.
9. Self-quarantine animals with questionable sysmptoms.
10. If you have mules, isolate them from horses since recent studies suggest mules can be silent carriers of the virus.

The time of exposure to illness of EHV-1 is typically two to 14 days. By self-quarantining animals with questionable symptoms, vaccinating horses for EHV-1 and West Nile virus, and practicing good biosecurity on the farm and during travel, horse owners can do a lot to help prevent further spread of the virus.

We’ll be sure to provide any updates here on the AgBriefs blog.