Equine herpesvirus 1

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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.[1] Abortion usually occurs in the last four months of gestation, two to four weeks after infection of the mare.[2] 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), however its efficacy is questionable.

The virus cross-reacts with Equine herpesvirus 4 in many serological laboratory tests. Commercial diagnostic tests are available to distinguish the two viruses using monoclontal antibody based reagents. The virus is easily isolated in cell culture and can be readily detected during acute infection using molecular diagnostic methods such as polymerase chain reaction (PCR).

Recent molecular epidemiology studies have identified a single nucleotide polymorphism (SNP) which varies between EHV-1 field isolates and shows a highly statistically significant correlation with paralytic compared with non-paralytic disease outbreaks.[3] The SNP corresponds to a single amino acid change in the DNA polymerase enzyme, which is an essential enzyme for replication of viral DNA. This is a significant finding, suggesting that a point mutation in a single virus gene has a major impact upon likely disease severity during an outbreak.

In 2006, an outbreak of EHV-1 among stables in Florida resulted in the institution of various quarantine measures.[4] The outbreak was determined to have originated with several horses imported from Europe via New York, and then shipped to Florida.[5]

Equine Herpes Virus Myeloencephalopathy (EHM)[edit]

Equine Herpes Virus Myeloencephalopathy (EHM) is the neurotropic form of EVH-1, most often attributed to mutant or neuropathogenic strains of EVH-1. There is currently no licensed vaccine against EHM and no treatment other than palliative care.[6]

The disease is highly contagious, and can spread through the air as well as through objects that have been in contact with infected horses.[7]

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.[8]

References[edit]

  1. ^ Fenner, Frank J.; Gibbs, E. Paul J.; Murphy, Frederick A.; Rott, Rudolph; Studdert, Michael J.; White, David O. (1993). Veterinary Virology (2nd ed.). Academic Press, Inc. ISBN 0-12-253056-X. 
  2. ^ Carter, G.R.; Flores, E.F.; Wise, D.J. (2006). "Herpesviridae". A Concise Review of Veterinary Virology. Retrieved 2006-06-08. 
  3. ^ Nugent J, Birch-Machin I, Smith K, Mumford J, Swann Z, Newton J, Bowden R, Allen G & Davis-Poynter N. "Analysis of Equid Herpesvirus 1 Strain Variation Reveals a Point Mutation of the DNA Polymerase Strongly Associated with Neuropathogenic versus Nonneuropathogenic Disease Outbreaks". Journal of Virology. Retrieved 2007-02-02. 
  4. ^ "Equine Herpes Virus type1 Status Report – Florida". Florida Department of Agriculture and Consumer Services. Archived from the original on 2007-01-06. Retrieved 2007-01-05. 
  5. ^ "Florida Department Of Agriculture And Consumer Services Continues Investigation Into Horse Virus Outbreak". Florida Department of Agriculture and Consumer Services. Retrieved 2010-12-27. 
  6. ^ "Equine Herpesvirus (EHV) Myeloencephalopathy". United States Department of Agriculture, Animal and Plant Health Inspection Service. Retrieved August 16, 2011. 
  7. ^ "USDA - APHIS - Animal Health Surveillance & Monitoring - Equine Herpes Virus". United States Department of Agriculture, Animal and Plant Health Inspection Service. Retrieved August 16, 2011. 
  8. ^ "Equine Herpesvirus (EHV-1) - Final Situation Report June 23, 2011". United States Department of Agriculture, Animal and Plant Health Inspection Service. Retrieved August 16, 2011.