What is Equine Herpesvirus?
Equine herpesvirus (EHV) is a family of equine viruses named by numbers including EHV-1, 2, 3, 4 and 5 with EHV-1,3,4 posing the most risk for domestic horses. EHV is a common DNA virus that occurs in horse populations worldwide. The two most common species are EHV-1 and EHV-4.
EHV-1 and EHV-4 most often cause a respiratory disease which is usually mild and self-limiting, and both can cause abortion. EHV-1 and EHV-4 (very rare) can cause the neurologic form of the disease (equine herpesvirus myeloencephalopathy (EHM)) which creates damage to the spinal cord and can be fatal. EHV-3 causes coital exanthema, a venereal disease which affects the external genitalia. Horses can be carriers of EHV with no clinical signs and can spread the disease to other horses. Testing and quarantining affected horses in isolation is the primary way to control the disease. Vaccines are available but do not completely prevent any form of the disease.
Clinical Signs
EHV-1:
- Fever
- Nasal discharge
- Lethargy/Depression
- Neonatal death
- Late-term abortion
- Neurologic disease
EHV-4:
- Fever
- Nasal discharge
- Lethargy
- Neonatal death
- Late-term abortion
- Rarely neurologic disease
Diagnosis: EHV-1 and EHV-4 are diagnosed through PCR testing by nasal swab, buffy coat sample (centrifuged blood), virus isolation from blood, or a significant increase in antibody titer in serum samples collected 2-3 weeks apart.
Treatment: Supportive care and rest are the chief treatments. Non-steroidal anti-inflammatory medications, such as phenylbutazone (Bute) or flunixin meglumine (Banamine) are used to control fever, pain, and inflammation. In some cases, antivirals and heparin are used.
Prevention: Vaccinations are available to help prevent the respiratory and abortive form of EHV-1 and EHV-4; there is currently no vaccine labeled for the prevention of the neurologic form of EHV-1 (EHM). The best method of protection is always to maintain current vaccinations on all horses on your property and to follow correct biosecurity protocol when bringing new horses onto your premises or when travelling with your horse.
Biosecurity: EHV is spread via aerosol particles from nasal discharge or from contaminated surfaces including people, clothing, feed and water, implements, and stalls; isolation is critical to preventing spread of the virus. Proper biosecurity measures include extensive disinfection of surfaces and equipment that come in contact with affected horses