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ALERT Equine Herpesvirus (EHV-1) Health Alert

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An outbreak of neurologic equine herpes virus (nEHV) has been confirmed on a single premises in southern Saskatchewan. The first symptoms noted were sporadic abortions (6) in a group of 70 late-term brood mares, followed by severe neurological symptoms in 5 horses which were subsequently euthanized. Equine herpes virus -1 (EHV-1) was confirmed by PCR on June 4. The premises has self-quarantined, under supervision of the herd veterinarian; it is anticipated that all animals currently on the premises will not be moved for a period of several months. No animals were moved off the premises in the weeks prior to the outbreak. Animal movements onto the farm in the weeks prior to the outbreak are being investigated to try to identify a potential source of introduction of the virus.

More details can be found in the following document from OMAFRA.


CURRENT EQUINE DISEASE OUTBREAK ALERTS AND INFORMATION - Canadian Animal Health Surveillance System (CAHSS) Equine Surveillance Network

Horse owners your attention to where you travel and commingle is important to the health of horses. Keep detailed health and travel records and consult a veterinarian if you detect any health irregularity. 

Ongoing recommendations:

  • All horse owners have been asked to carry out normal biosecurity protocols
  • Any horse that has has been in contact with this high risk horses should be monitored closely for signs of respiratory or neurological disease
  • Any horse showing signs of neurologic or respiratory disease should contact their veterinarian
  • To avoid spreading nEHV-1, direct and indirect contact with sick and high risk horses should be avoided.
Biosecurity Information

 Overview of equine herpes virus (EHV-1 & 4) 

- Katharina L Lohmann Med Vet, Ph.D. Western College of Veterinary Medicine, U of S, Saskatoon, Saskatchewan, Canada

Equine herpes virus (EHV) is a common virus occurring in horse populations worldwide. The most common strains are EHV-1 and EHV-4. EHV-1 can cause respiratory diseases, abortions and neurologic disease, while EHV-4 typically causes respiratory disease but can also cause abortions.

EHV-1, but not EHV-4, has been identified as a cause of abortion outbreaks and outbreaks of neurologic disease. There is no risk of transmission to humans.

Neurologic disease due to EHV-1 infection, also called equine herpes virus myeloencephalopathy (EHM), results from widespread damage to blood vessel endothelium, including damage to the blood-brain barrier. Clinical signs include fever, ataxia (incoordination) most commonly affecting the hind limbs, and bladder dysfunction leading to urine retention and incontinence. Severely affected horses may become recumbent and unable to rise; however, horses generally remain bright and often continue to eat and drink. The disease is often suspected based on clinical signs and can be confirmed through testing for the presence of antibodies in blood, virus isolation and molecular tests (PCR). Treatment is mostly supportive and may include anti-inflammatory medication, intravenous fluid therapy, and repeated bladder catheterization. Specific antiviral medications are under investigation. Several vaccines against EHV-1 are available; however, none of the currently available vaccines state any claim for protection against the neurologic form of EHV-1 infection.

Herpes viruses establish latency, meaning that the virus persists in the horse for the long term, possibly for life, without any associated clinical signs. Latent infection with EHV-1 is thought to be common in North America; however, only few studies have reported precise numbers. Re-activation of latent infections, and subsequent disease and/or shedding of virus may occur in situations of stress, which may include transportation, mingling of horses, and concurrent disease.

EHV-1 is transmitted primarily by aerosol and through direct and indirect contact. Aerosol transmission occurs when infectious droplets (coughing or snorting) are inhaled. Shedding by the respiratory route in horses with EHM typically lasts for seven to 10 days following the onset of disease but can persist longer. A 28-day isolation period is therefore generally recommended after the diagnosis has been established.

In addition to direct contact between horses (touching noses), indirect transmission is an important route of transmission of the virus. Indirect transmission occurs when infectious materials (nasal secretions etc.) are moved between infected and un-infected horses by people or fomites (inanimate objects). Indirect contact can be minimized through routine hygiene measures such as hand washing and hand disinfection and by avoiding sharing of equipment such as feed buckets and waterers, grooming supplies and tack among horses. People who have touched or otherwise come in contact with infected horses should change their clothes and thoroughly clean and disinfect their hands before handling other horses.

Boarding facilities, show grounds and other venues in collaboration with the attending veterinarian should develop a biosecurity protocol specific to their situation. Biosecurity considerations include isolation and testing of new horses upon arrival, requirements for health certificates and/or vaccination, and instructions for hygiene measures while on the premises. Attendants at equine events should familiarize themselves with any biosecurity instructions and minimize direct and indirect contact between their horses and others. Horses developing clinical signs of disease should be evaluated by a veterinarian in order to establish a diagnosis, develop an appropriate treatment plan and institute necessary biosecurity measures in case of an infectious disease.

For more information:

We all have a duty to preserve the health and welfare of our horses.

Last Updated ( Tuesday, 11 June 2019 09:04 )