EHV: Understanding Equine Herpesvirus
Equine Herpesvirus (EHV) sounds like something very scary when we hear about a local breakout. It’s actually EHV-1 that causes the most concern. EHV is a family of viruses and according to the American Association of Equine Practitioners, it is found in most horses around the world. In all, there are 9 specific EHV strands. But strains of 1, 3, and 4 are the most serious.
Understanding the strains of EHV
The three most serious forms of EHV are labeled 1, 3, and 4. Forms that cause neurological issues may also be called herpesvirus myeloencephalopathy (EHM).
| EHV 1 | Can present itself in horses in 4 different ways: neurological, respiratory, abortion, and neonatal |
| EHV 3 | Causes coital exanthema, a venereal disease, that affects external genitalia. It does not seem to affect fertility. |
| EHV 4 | Is generally found in foals and causes a nonfatal upper respiratory disease. Rarely it will cause neurological issues. |
How EHV spreads
EHV spreads through respiratory secretions and passes from horse to horse. An infected horse spreads the disease when it blows its nose or coughs. A worker at a barn could spread the virus by becoming contaminated inside one stall and then moving around the barn spreading the contamination. Some examples of possible spread sources beyond a cough or sneeze are:
- Water nozzle allowed to touch the water in multiple water buckets.
- Community water buckets.
- Feeding multiple horses by hand without handwashing in-between.
- Sharing tack or grooming equipment between horses.
- A contaminated horse trailer.
EHV and vaccines
There are vaccines for EHV that can protect your horse against EHV’s respiratory disease and abortion. Unfortunately, there is no vaccination that will protect against the neurological strain of the virus. What is even more concerning is that some research is linking outbreaks of EHV to the frequency a horse is vaccinated for EHV.
Preventive Measures
Implementing good biosecurity practices when you travel with your horse is a good start to preventing the spread of EHV. Some practices to include are:
- Don’t allow horses to meet.
- Don’t pet other horses at the event.
- Don’t share tack, equipment, or stall cleaning tools.
- At home keep traveling horses separate from those that don’t leave the farm.
- And take temperatures frequently. A high temperature can be the first sign of EHV or other diseases.
Diagnosis
If your horse is displaying signs of infection, immediately isolate the horse from healthy horses and call your veterinarian. While waiting for the vet, be sure to disinfect all mucking equipment, tack, grooming tools and other items that may have come in contact with the horse. Your veterinarian will collect a nasal swab and blood sample.
Clinical Signs:
- Fever
- Difficulty urinating
- Nasal discharge and cough
- Depression
- Head tilt
- Loss of tail tone
- Stumbling or weakness in hind limbs
- Unable to rise once down
Here is an excellent video hosted by SmartPak on the Equine Neurological Exam process.
It’s important to note that not all horses display clinical signs and may be a carrier of the virus.
References and additional reading
“FAQ: Equine Herpesvirus (EHV) | AAEP.” Home | American Association of Equine Practitioners, https://aaep.org/horsehealth/faq-equine-herpesvirus-ehv. Accessed 17 Mar. 2021.
“Frequently Asked Questions Regarding Equine Herpesvirus » Large Animal Hospital » College of Veterinary Medicine » University of Florida.” Large Animal Hospital » College of Veterinary Medicine » University of Florida, https://largeanimal.vethospitals.ufl.edu/frequently-asked-questions-regarding-equine-herpesvirus/#spread. Accessed 17 Mar. 2021.
“Preventing EHV-1: What Can You Do? – The Horse.” The Horse, https://www.facebook.com/TheHorse, 11 Sept. 2018, https://thehorse.com/160371/preventing-ehv-1-what-can-you-do/.
