Equine Herpes Virus (EHV) Outbreak – Information for Owners

There has been a neurologic Equine Herpes Virus-1 (EHV-1) outbreak in the South of England ongoing since January 1st 2020. Thankfully due to a rapid and responsible response from the affected yard and great coordination among the many veterinary practices in the area, the disease appears to be very confined thus far.

The virus can spread via inhalation of droplets from coughing when present, or from direct or indirect transmission via nasal secretions. The virus can be viable in the environment (clothes, barns, stables etc) for several weeks. In order to reduce the incidence of infectious outbreaks in at-risk premises, biosecurity rules should be applied including changing clothes or wearing overalls when handling the new horse, using boot covers/foot dips in and out of the stable, washing hands between horses, mucking out the isolation horse last and taking rectal temperature twice daily. It is important to remember that most disinfectants only work on a surface which has first been cleaned.

Signs of EHV-1 infection may include any of the following:

Rectal temperature above 38.5°C
Nasal discharge, ocular discharge, cough
Leg-filling
Dullness, lethargy, abnormal behaviour Incoordination or abnormal posture, urine dribbling Late abortions in pregnant mares (usually > 7 months

If any of these clinical signs occur, please contact your vet for advice: laboratory testing can be done on nasal swabs and/or blood testing depending on the case. If a case of EHV
is confirmed then horses which have potentially come in to contact with that animal may need to be isolated and monitored, usually over a 2 week period, to ensure they are free of the disease. Horses which have not had any contact with clinical cases or at-risk animals are not subject to any movement restrictions, but increased biosecurity measures and vigilance is advised during an outbreak.

A vaccine is available with inactivated EHV type 1 and type 4, which has been shown to reduce the incidence of respiratory disease and viral shedding, as well as reducing abortions due to EHV-1. There is no indication that the vaccine would help prevent the neurological form of EHV-1 in individual horses. This means that vaccination could be useful for maintaining herd immunity and reducing spread of the virus, but not necessarily protect individuals against disease.

This document was prepared based on the contributor’s knowledge and current experience of the EHV outbreak and will be reviewed as necessary.