24/7 EMERGENCY 520-749-1446

By:  Kate Woodard, DMV
Reata Equine Veterinary Group LLC

Every few years, Equine Herpesvirus (EHV) makes its way into the horse world headlines. We hear terrifying stories about quarantine and crippling neuropathies, often leading to fear, blame, and miscommunication of information. Then, the commotion fades away without any clearer understanding.

The American Association of Equine Practitioners has excellent resources for horse owners to set the record straight. Please follow any of the below links for detailed information.





We’d also like to clear up some of the most common questions we receive at the office during EHV related outbreaks.

  1. I hear about lots of EHV types. What do they cause?

Equine herpesvirus is ubiquitous within the equine population. Of the nine types identified, EHV-1, 3, and 4 present the most serious health risks for horses here in the United States. When central nervous system impairment is present in conjunction with EHV infection, it is described as equine herpesvirus myeloencephalopathy or EHM. Neurologic signs are caused by disruption of the blood brain barrier, leading to inappropriate clotting and tissue death.

EHV-1: neurologic form, respiratory form (rhinopneumonitis), abortive form, and neonatal death

EHV-3: venereal disease (coital exanthema)

EHV-4: respiratory form (rhinopneumonitis), uncommonly abortive or neurologic forms

  1. Doesn’t my regular rhino/flu booster protect against EHV? Does this mean my horse is protected against neurologic disease?

Herpesvirus vaccines are specifically labeled against the respiratory and abortive forms of the disease. THERE IS NO LICENSED VACCINE FOR PREVENTION OF NEUROLOGIC DISEASE. There are some studies that suggest that giving a vaccine booster during an outbreak may reduce viral load and shedding, but this remains controversial and should be discussed on an individual basis.

  1. How is EHV-1 transmitted?

EHV-1 is transmitted by contact with respiratory secretions. This can happen directly, such as through coughing or nose to nose contact. It can also occur indirectly via human clothing, shared tack or buckets, or contaminated trailers.

  1. Do all horses with neurologic signs have to be euthanized?

No. If the horse is adequately vaccinated to rule out significant human health risk (i.e. rabies) and responds favorably to palliative therapy, euthanasia may not be required. Horses that do survive often have some level of lasting neurologic impairment.

  1. How long does quarantine last? How long does it last in the environment?

Quarantine lasts for 28 days after the most recent identified case. In most circumstances, the virus remains present in a contaminated area for about a week, but can be significantly longer with poor biosecurity practices.

  1. What can horse show managers do to reduce risk?

Some practical considerations include: contacting the state veterinarian 7-10 days prior to horse arrival for news of recent outbreaks, requiring a Health Certificate by an accredited veterinarian within 10 days of horse departure, evidence of EHV-1 vaccination in the past 6 months (preferably by a veterinarian to ensure product quality and correct administration), and high biosecurity standards.

**Please remember that even powerful disinfectants will not work in the presence of organic material, so it is important to thoroughly wash buckets, stall walls, bars, brushes, hands, etc. before applying a disinfecting product.

  1. When should I call a vet?

Any time a horse shows neurologic impairment (stumbling, poor coordination, circling, head pressing, weakness, etc.) or has a temperature above 102, contact your veterinarian immediately.

Other signs that may indicate infection include nasal discharge, cough, poor appetite, depression, or swollen lymph nodes. While these non-specific signs may not require a visit, your veterinarian can help decide the best course of treatment.

Finally, if you are returning from a show or planning to travel during a known outbreak, alert your veterinarian so you can create a preventative plan of action.

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