Equine Herpes Virus: What to Know
With the recent cases of equine herpes virus myeloencephalopathy (EHM) being so close to home, we thought this would be a good time to educate horse owners about this disease. EHM has been diagnosed in two horses this year close to the Minot area: one in Mckenzie County, ND and one in Clay County, MN.
What is equine herpes virus (EHV)?
These are viruses that are found in most horses throughout the world. Due to its highly contagious nature, almost all horses have been exposed/infected with EHV but only a small percentage develop serious illness.
All in the Family
The equine herpes virus is a family of viruses and it is quite large. Currently, nine different EHVs have been identified but EHV 1, 3, and 4 pose more health risks for our horses.
· EHV-1: the one we worry about the most because it can cause abortion, respiratory disease, neonatal death and EHM
· EHV-3: causes coital exanthema which affects the external genitalia but doesn’t appear to affect fertility
· EHV-4: commonly associated with a mild-moderate upper respiratory tract infection
We do not fully understand the reason(s) why some horses develop the neurologic form of the disease.
How does EHV spread?
This is a highly contagious virus and can spread by direct horse-to-horse contact through nasal secretions but can also be spread by contact with virus contaminated objects. The objects can be anything from tack and grooming supplies to feed/water buckets and even your hands and clothing! The virus can survive up to 7 days in the environment under normal circumstances.
Prevent the spread!
Proper hand hygiene is just as important as cleaning your equipment. Washing hands with soap and water and making sure to completely dry them is adequate. You can also use an alcohol based hand sanitizer. When cleaning equipment and horse housing areas, it is very important to wash and rinse surfaces to remove organic material. Removing as much organic material as possible will make your disinfectant more effective. Fortunately, the virus is easily killed by most conventional disinfectants and detergents.
Signs to watch out for
After a horse is infected, signs can start to occur in as little as 24 hours after initial exposure to the virus. Respiratory infections often have serous (clear/thin) or mucoid (yellow/thick) nasal and ocular discharge but without a lot of coughing. Neurologic disease appears suddenly with rapid progression of clinical signs (peak intensity within 24-48 hours from onset). Clinical signs of the neurologic disease may include:
· Nasal discharge and fever
· Incoordination/weakness in the hind limbs
· Loss of tail tone
· Lethargy
· Urinary incontinence/inability to urinate
· Head tilt
· Leaning against fence or wall for balance
· Inability to rise/dog-sitting
Diagnosis of EHV is based on clinical signs and isolation of the virus from blood and/or nasal swabs.
Treatment of EHV
Contact a veterinarian for physical examination and diagnostic testing upon discovering any fever of unknown origin (FUO), respiratory signs or neurological signs. Due to the fact that a virus causes the illness, antibiotics are not effective against it and are not usually recommended. Rest and good nursing case should be provided which means keeping the horse comfortable, hydrated, and eating. Horses with severe neurologic disease may need 24 hour care at a specialty clinic to provide assistance with urination, defecation and even standing. Prognosis for severe neurologic disease is poor. Uncomplicated respiratory disease cases usually recover in a few weeks.
How can I prevent EHV?
Prevention doesn’t have to be complicated and it all boils down to appropriate vaccination and common-sense biosecurity. There are several EHV vaccines on the market, however, none carry the claim preventing the neurological form of the disease. This makes working with your local veterinarian extremely important for development of a vaccination program tailored to your horse(s). There is value to vaccinating your horse(s) against EHV because it has been shown to reduce severity and duration of respiratory and reproductive forms as well as decrease virus shedding in nasal secretions. Boostering EHV vaccine about every 3 months during show/rodeo season is beneficial to increase immunity to the virus. Some biosecurity measures were mentioned earlier.
Related resources:
https://aaep.org/horsehealth/faq-equine-herpesvirus-ehv
https://www.smartpakequine.com/content/Equine-Herpes-Virus
https://www.nd.gov/ndda/disease/equine-herpesvirus-1
http://equinediseasecc.org/alerts/outbreaks?page=49
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