Michigan Horse Tests Positive for EHM
In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. | Photo: Stephanie L. Church/The Horse
On Nov. 18, officials at the Michigan Department of Agriculture and Rural Development (MDARD) confirmed a horse in Oakland County, Michigan, with neurologic equine herpesvirus myeloencephalitis (EHM). The affected 18-year-old Thoroughbred gelding experienced onset of clinical signs on Nov. 15. Signs consisted of hind limb ataxia (loss of control of body movements) and urine retention. The horse has been reported as affected and alive.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and equine herpesvirus myeloencephalitis (EHM, the neurologic form).

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and a nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anywhere from two weeks to several months following infection with EHV-1.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop

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