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Equine Herpes Virus

Vet injecting horse


Equine herpesvirus (EHV) is a contagious viral infection which can cause respiratory disease, abortions and neurological disease.

There are two main types of EHV which cause disease in horses, both of which are widespread and therefore all horses will be at risk of infection at some stage of their life.

EHV -1: This strain can be severe in its effects, causing abortion and neurological disease

EHV-4: This strain mostly causes respiratory disease.

The main concern for the equine population as a whole is the way the disease persists in horses. Once a horse is infected, that individual can harbour the virus throughout its life and potentially shed the disease to other horses without showing any outward signs. Re- infection and shedding from infected horses tends to happen when they are stressed – typically moving yards or in hard work

The symptoms can be very similar to equine flu. They can include high temperature, snotty or runny nose, dry cough, lethargy, loss of appetite, swollen neck glands, and abortion in pregnant mares. Less commonly, horses can devleop problems with their nervous system such as appearing weak and wobbly on their hind legs often accompanied by urinary incontinence. Even without showing signs, it is possible the EHV could affect the athletic performance of a horse by putting strain on its immune system.

EHV will obviously put your horse out of work for a number of weeks while it recovers from the infection. EHV does not stimulate significant natural immunity after initial infection, in fact the horse is susceptible to re- infection after just a few months. Vaccination has been proven to reduce clinical signs and decrease viral shedding and is an important part of a comprehensive protection strategy.



1. Lunn DP et. al. (2009) EHV-1 Consensus Statement. J Vet Intern Med 2009;23:450–461
2. Durham A (2011) How to diagnose: Neurological EHV. BEVA congress proceedings. 38-29
3. Marr C (2016) Approaches to managing and treating equine herpesvirus. Vet Times, December 6, 2016
4. Allen (2002) Respiratory Infections by Equine Herpesvirus Types 1 and 4 In: Equine Respiratory Diseases, P. Lekeux (Ed.)Publisher: International Veterinary Information Service (www.ivis.org), Ithaca, New York, USA.( 28-Feb-2002 )