Equine Herpesvirus 1

Virus, Enveloped

VirusEquine Herpesvirus 1
StructureEnveloped
GenomeDouble stranded DNA
FamilyHerpesviridae
Primary HostHorses
Disease(s) CausedEquine rhinitis
SymptomsRespiratory illness, abortion
Potential ComplicationsEncephalomyelitis
Transmission ModeContact with infected secretions, aerosols
Sites of Community OutbreaksStables, ranches

Importance of Equine Herpesvirus 1

Equine Herpesvirus 1 (EHV-1) is an enveloped member of the Herpesviridae family. EHV-1 affects horses and is highly prevalent in horse populations worldwide. It is one of the main infectious causes of abortions in horses. Some strains of EHV-1 can also cause a neurologic disease, encephalomyelitis.

As with other herpesviruses, EHV-1 is capable of establishing latent infection, reactivating at times of stress. EHV-1 causes respiratory disease after primary infection, with symptoms including fever, nasal discharge, and loss of appetite. In some cases, the central nervous system is affected. Symptoms of nervous system infection include loss of coordination, incontinence, and in more severe cases, paralysis and death. If a mare is initially infected or experiences reactivation of a latent infection during pregnancy the virus can be passed to the fetus, resulting in a sudden abortion. Infections late in gestation can result in a full-term live birth, but such foals are often very ill and die within a few days.

Infection with EHV-1 in foals usually occurs in the first few weeks or months after birth. It has been shown that the source of infection is lactating mares with latent infections. The infection is then spread from foal to foal.

EHV-1 can have serious economic consequences. In groups of pregnant mares, abortion storms can occur, leading to significant loss of animals. Outbreaks of encephalomyelitis can lead to movement restrictions which disrupt training, racing, and breeding schedules for competitive animals.

Importance of Disinfection

As an enveloped virus, EHV-1 is sensitive to inactivation by environmental factors, such as temperature and humidity.

EHV-1 is transmitted primarily via direct or indirect contact with infectious fluids from either an aborted fetus or a shedding animal. Aerosol transmission may also occur, as noted by cases where abortion storms have occurred among mares housed in separate stalls. It is important to ensure that stalls where mares who aborted have been housed are thoroughly disinfected before being used again. As with other enveloped viruses, EHV-1 is susceptible to a range of disinfectants, including quaternary ammonium compounds and chlorine-based disinfectants.

Several vaccines exist for EHV-1. Some are licensed for protection against respiratory illness only, while others are also licensed for prevention of abortion. No vaccine is licensed to prevent encephalomyelitis. Immunity resulting from vaccination is not lasting. Revaccination is recommended at 6-month intervals, with more frequent intervals suggested for pregnant mares.

References
  • "Equine Herpesvirus (Rhinopneumonitis)." Equine Herpesvirus (Rhinopneumonitis). American Association of Equine Practitioners, n.d. Web. 21 Jan. 2016.
  • Lunn, D.P., Davis-Poynter, N., Flaminio, M.J.B.F., Horohov, D.W., Osterrieder, K., Pusterla, N. and Townsend, H.G.G. (2009), Equine Herpesvirus-1 Consensus Statement. Journal of Veterinary Internal Medicine, 23: 450–461.
  • Tsujimura, Koji et al. “Efficacy of Five Commercial Disinfectants and One Anionic Surfactant against Equine Herpesvirus Type 1.” The Journal of Veterinary Medical Science 77.11 (2015): 1545–1548. PMC. Web. 21 Jan. 2016.
  • Van Maanen, C. "Equine herpesvirus 1 and 4 infections: an update."Veterinary Quarterly 24.2 (2002): 57-78.