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Equine Herpes Virus-1 (EHV-1) outbreak in France.

The equestrian community has been alerted by the FEI that there has been a recent Equine Herpes Virus-1 (EHV-1) neurological outbreak in France.


It is reported that the outbreak is linked to a national event that took place in Le Mans from 1st November 2024 to 3rd November 2024, and as of 20th November 2024, has resulted in fatalities and cases in three different French departments.


An FEI event took place at the same venue in the following week (8-11 November 2024). The FEI horses were housed in different stables than the horses competing in the national event and there were no direct contacts between the national and FEI horses at Le Mans.


EHV-1 is an air-borne disease that can be transmitted up to five metres via coughing, but also through direct contact, via people and shared equipment. It can cause respiratory and neurological signs, abortion in pregnant mares and death of young foals.


In response to the outbreak, we request that the community remains vigilant and monitors the health of their horses carefully, for clinical signs of infectious disease. Further information relating to EHV-1 can be found on the EHV-1 hub.


Words adapted from correspondence received from the FEI on 22nd November 2024.


What is the Equine Herpes Virus?


Equine Herpes Virus is a contagious disease that affects horses. Although there are nine strains of the virus, Equine Herpes Virus-1 (EHV-1) and Equine Herpes Virus-4 (EHV-4) are most commonly seen. Affected horses may suffer respiratory disease, neurological disease and abortion in pregnant mares. Young foals are also at risk and can die from the infection.


How is the disease transmitted?


Equine Herpes Virus can be transferred through the air from horse to horse up to distances of 5 metres. Horses can become infected and bring the disease to their home stables and transmit the virus to other horses through close contact and coughing. The virus can also be transmitted on clothing and yard equipment by people working with infected horses. Horse transport is also a risk for disease transmission. Lorries and trailers in which infected horses have travelled may be contaminated with the virus and transmit the disease to others. Thorough cleaning of all equine transport vehicles must be carried out between shipments. Stables must be thoroughly cleaned and disinfected between horses.



What clinical signs should I look out for?


The clinical signs of Equine Herpes Virus depend on the strain of the virus affecting the horse.


Horses suffering from EHV-1 can develop a fever, respiratory disease such as coughing and clear nasal discharge. Some horses may develop neurological signs leading to lack of coordination, weakness, difficulty in urinating and defecating and becoming recumbent (unable to stand up). Horses that are severely affected by the neurological form of the disease may have to be euthanised. The virus is also a common cause of abortion in pregnant mares and the death of young foals.


EHV-4 infections commonly result in horses developing a fever, cough and clear nasal discharge. The virus can also cause abortion in pregnant mares, but this is less commonly seen.


Infected horses can develop complications such as secondary bacterial infections.



I suspect my horse has EHV. What should I do?


Horses showing the early signs of the disease must be isolated and examined by a veterinarian. Clinical signs are often seen within approximately 10 days of being in contact with the virus. Since infected horses can show similar clinical signs to other diseases, your veterinarian should take nasopharyngeal swabs and blood samples for laboratory analysis in order to confirm the diagnosis.


Horses that have been in-contact with the affected horse must be identified, isolated and tested for the disease. The movement of all horses on and off the affected stables site must be restricted and strict biosecurity measures enforced. The measures include foot baths, hand disinfection and the prevention of equipment sharing.


How can I protect my horses?


A vaccine against EHV-1 and EHV-4 is available but does not protect the horse against the neurological form of the disease. However, the use of the vaccine can help to reduce the shedding of the virus, its transmission to other horses and the severity of the respiratory form of the disease. The vaccine should not be used during an outbreak at stables.


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