Equine herpesvirus 1
| Equine herpesvirus 1 | |
|---|---|
| Virus classification | |
| Group: | Group I (dsDNA) |
| Order: | Herpesvirales |
| Family: | Herpesviridae |
| Subfamily: | Alphaherpesvirinae |
| Genus: | Varicellovirus |
| Species: | Equine herpesvirus 1 (EHV-1) |
Equine herpesvirus 1 (EHV-1) is a virus of the family Herpesviridae that causes abortion, respiratory disease and occasionally neonatal mortality in horses. Initial spread of EHV-1 by a newly introduced horse through direct and indirect contact can lead to abortion and perinatal infection in up to 70 percent of a previously unexposed herd. Abortion usually occurs in the last four months of gestation, two to four weeks after infection of the mare. Perinatal (around the time of birth) infection can lead to pneumonia and death. Encephalitis can occur in affected animals, leading to ataxia, paralysis, and death. There is a vaccine available (ATCvet code QI05AA11 (WHO)), however its efficacy is questionable.The virus varies in severity from sub-clinical to very severe. Most horses have been infected with EHV-1 but the virus can become latent and show no signs and never be an issue. In 2006, an outbreak of EHV-1 among stables in Florida resulted in the institution of various quarantine measures. The outbreak was determined to have originated with several horses imported from Europe via New York, and then shipped to Florida.
EHV-1 has two main strains that have been isolated. D752 is the strain that is more correlated to the neurological outbreak of this virus and the non-neurological outbreaks are more closely associated with N752 . Some horses do show the neurological effects without the D752 isolate but the majority are with this strain. A mutation results in both these two different main strains, D752 is the presence of aspartic acid and the N752 is the presence of asparagine. 80–90% of neurological disease is caused by the D752, and 10–20% for N752. The neurological strain has been named Equine Herpesvirus Myeloencephalopathy, or EHM. There is currently no licensed vaccine against EHM and no treatment other than palliative care. The disease rose to worldwide public prominence in early 2011, due to an outbreak centered on the National Cutting Horse Association (NCHA) Western National Championships held in Ogden, Utah from April 29 to May 8, 2011. The outbreak lasted approximately two months, generating 90 confirmed cases of the disease, spread over 10 American states, and resulting in the deaths of 13 horses before it was declared contained by the US Department of Agriculture.
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