Veterinary Alert

A 10-year-old pregnant female Quarter Horse in Clearwater County tested positive for Equine Herpesvirus-1 (EHV-1) in early February. Neurological symptoms combined with the EHV-1 infection is consistent with Equine Herpesvirus Myeloencephalopathy (EHM).

The mare was found unable to stand and unable to rest sternally on Feb. 1. The animal was treated with NSAIDs and corticosteroids. A veterinarian examined the mare on Feb. 2 and found the animal in lateral recumbency, hypothermic with poor rectal tone and leaking urine. The mare was euthanized due to poor prognosis. 

Testing of the mare at the North Dakota State University Veterinary Diagnostic Laboratory confirmed the presence of EHV-1, the virus that causes EHM. On Feb. 5, four other mares on the premises were found to be symptomatic and also tested positive for EHV-1. The other mares are recovering. A total of 34 horses are under quarantine at the property.

Equine Herpesvirus Myeloencephalopathy

EHM is a disease impacting horses, which develops from an EHV-1 infection. The virus is easily spread between horses and can remain inactive for long periods of time. Horses can be exposed and not suffer serious illness, yet some develop the neurological form of the disease, myeloencephalopathy. Minnesota horses with a confirmed EHM infection (and those exposed to EHM-infected horses) must be quarantined to prevent further spread of the disease. Infected horses are treated with supportive care, because there is no cure for EHM.

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