Outbreak of EHV-1 in Valencia – Update 16th March 2021

This article is updated with a table with more details on treatment of EHV-1 at the bottom of the article.

ECEIM guidelines for dealing with returning horses from EHV-1 outbreaks

In light of the current outbreak of Equine Herpes Virus-1 (EHV-1) the European College of Equine Internal Medicine has decided to provide the following guidelines available to anyone dealing with horses returning from Valencia/Spain or as general guidelines to deal with such outbreaks. Horse owners should seek advice from their veterinarian but may wish to quote these guidelines.

EHV-1 is a common virus that affects horses worldwide and can cause mild respiratory disease, and on occasion, serious complications of neurological gait deficits. Clinical signs may include nasal discharge, cough, a rectal temperature greater than 38.3°C/101.5°F, enlarged submandibular lymph nodes and oedema of the limbs and/or ventral abdomen. Neurological signs can be any of urinary/faecal incontinence, penile prolapse, weak tail, being unsteady on its feet or even being unable to stand, which may deteriorate requiring euthanasia. Owners of horses suffering from any on these signs or in contact with a horse with any of these signs please contact your veterinarian immediately.

All horses returning home from Valencia/Spain or from a show where horses from Valencia were present should undergo the following protocol:

  1. Undergo appropriate quarantine (separated from other horses and ponies by distance, airspace or building, and supported by separate personnel and equipment).
  2. Strict hygiene rules apply for contact with horses (hand hygiene, protective clothing or a change of clothes including shoes, use of separate equipment).
  3. Home-coming horses should be tested upon arrival (Day 1 nasal swab PCR) and isolated in quarantine. If arrival swabs are all negative, and no clinical signs (see point 5) were noticed it is safe to lift quarantine after 28 days.
  4. To shorten quarantine time all isolated horses should be tested again on day 14. A nasal swab is collected and submitted for PCR testing for EHV-1 to an accredited laboratory on that day, and a second swab should be submitted immediately when the day 14 swab returns with a negative test result (this strategy increases the test sensitivity to above 80%). If all tests are negative (including day 1), and there were/are no clinical signs consistent with EHV-1 infection, horses can return to the main group.
  5. Alternatively, paired samples for serology (antibody titer) obtained 14 days apart may also aid to detect recent exposure to virus but will not replace nasal swab testing.
  6. If horses travel together when returning to their home facility and do not show any abnormal clinical signs (point 5), they can all be isolated together. Any horse positive on a nasal swab from day 1 or showing clinical signs (see point 5) should be individually quarantined and tested.  If the group is tested by day 14 or any later time point and one sample is positive, the entire group needs to stay in quarantine until further notice and testing.
  7. Monitor for respiratory signs such as nasal discharge, cough, submandibular lymph node enlargement/sensitivity, and monitor for signs of limb/ventral oedema. Take rectal temperatures twice daily and report temperatures >38.3°C. Any of these abnormal signs should prompt EDTA-venous blood testing for EHV-1 viraemia (EHV-1 PCR testing via an accredited laboratory). Any positive PCR result during the quarantine period will postpone the release from quarantine.
  8. When dealing with a group of quarantined horses, a positive test result of an individual horse should prompt separation from the group and individual isolation.
  9. Exercising quarantined horses: light work, if possible outdoors, and not together with any of the horses that are not in quarantine. If this is not possible, the quarantined horses should be exercised after the remainder of the herd (e.g. at the end of day).
  10. Adjust feeding to the level of exercise.
  11. If a horse is already on NSAIDs for management of other conditions fever might be masked so if possible NSAIDs should not be used while the horse’s temperature is being monitored.
  12. Vaccination: It is not recommended to vaccinate horses in quarantine. Tetanus vaccination in case of emergency is allowed. Healthy EHV-vaccinated horses, with no fever, that were/are not in contact with the quarantined yard, can receive an EHV booster (not earlier than 4-6 weeks from first dose), but maximum immunity will be reached approx. 10 days later. Horses without EHV vaccination history will have maximum immunity 10 days after the second vaccination (booster), so it will take usually 6 weeks from the first dose to gain immunity. Considering the risk of quarantine breech on premises that host an isolated group, we do not recommend starting EHV vaccination on these premises. Horses on neighboring farms (fence line, distance, no exchange between farms) can start first dose or booster of their healthy animals. Keep in mind, some first-time vaccinates respond with swelling at injection site and/or a fever for 1 – 2 days. In general, horses that received a vaccine injection should be rested for 1 – 2 days, then on a light exercise schedule for the remainder of the week.

Update 16th March 2021

Equine Herpesvirus-1 therapy

Lutz Göhring, Karsten Feige, Marianne Sloet, Dominique De Clercq, Vinzenz Gerber, Orsolya Korbacska-Kutasi, Ignacio Corradini, Fernando Malalana, Ruth Morgan, Lisa Katz, René Van den Hoven, Marco Duz, Jessika-M. Cavalleri, Anne Couroucé

Once biosecurity/quarantine guidelines have been followed, there are numerous medical options for treatment of Equine Herpesvirus-1 (EHV-1) positive horses with and without clinical signs of Equine Herpesvirus Myeloencephalopathy (EHM). If a horse begins to show clinical signs of EHM, it is important to consider that intensive and committed nursing care plays a pivotal role in the management of these cases. This may include provision of soft bedding and helmets to protect the horse from head trauma, the use of indwelling urinary catheters and manual evacuation of the rectum and assisting the horse to stand (using slings) if possible. If the horse is unable to stand the horse should be maintained in sternal recumbency, and rolled to different sides every 2-4 hours. Monitoring and maintaining hydration is vitally important.

Table 2: Commonly used drugs for EHV-1 positive horses, both with and without clinical signs of EHM.

Download the table in PDF

RCT: Randomised Control Trial; CRI: Constant Rate Infusion; DMSO: Dymethyl sulphoxide;


For further advice please check www.eceim.info/diplomats to find a Recognised Equine Internal Medicine Specialist closest to you.

Lutz Göhring, Karsten Feige, Marianne Sloet, Dominique De Clercq, Vinzenz Gerber, Orsolya Korbacska-Kutasi, Marco Duz, Jessika-M. Cavalleri, Anne Couroucé


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