neurologic | Horse Racing Free Tips

Can A Horse That Has Had EPM Have A Relapse?

Equine protozoal myeloencephalitis (EPM) is a potentially devastating disease caused by a protozoa that horses ingest. Once the horse has been infected, the organisms can migrate to the central nervous system, causing inflammation and tissue damage to the spinal cord and brain.

A horse that has EPM can be incoordinated, lame or weak. Treatment involves the use of antiprotozoal or antiparasitic medication like diclazuril, ponazuril or sulfadiazine and pyrimethamine. These can reduce or eliminate the signs of EPM. Most cases of EPM respond to treatment, but horses may need more than one round of treatment weeks or months after their initial treatment.

EPM-causing protozoa are good at evading the immune response and surviving immune attacks, which makes them hard to eradicate. Additionally, a horse's immune response in the central nervous system is not as strong, additionally complicating treatment. Because of this, horses that have had EPM can relapse, though it is unclear how often this happens. One study showed a relapse in about 8 percent of horses within 90 days after the initial EPM treatment concluded. Evidence of relapses after longer periods of time also occur.

Multiple factors are involved in an EPM relapse, including the dose and type of drug used, as well as the variability of the individual horse to clear the organisms. A veterinarian caring for a horse that has another episode of EPM should investigate lengthening the duration of treatment.

Horse In PA Diagnosed With EHM

A 22-year-old Trakehner gelding that lived in Allegheny County, PA, was diagnosed with the neurologic form of equine herpesvirus-1 (EHV-1) on June 17 and euthanized, reported the Pennsylvania Department of Agriculture. A veterinarian was called after the horse showed signs of incoordination, abnormal urination and lying down without being able to rise. It is unclear if he had been vaccinated for the disease. An additional 39 horses boarded with the affected horse have been placed under official quarantine, reports The Horse.

EHV is highly contagious; it can cause respiratory issues and abortion in pregnant mares; it can also develop into the neurologic form of the disease, called equine herpesvirus myeloencephalitis (EHM). A horse that has the virus may have a fever, nasal discharge or cough; he may be uninterested in food or be depressed. Pregnant mares may show no symptoms of the virus before they abort, typically later in their pregnancies.

EHV-1 is spread through direct horse-to-horse contact as well as through contact with objects that have been contaminated by the virus, which includes human hands, equipment, tack, buckets, trailers and other such surfaces. The virus can be viable for between seven and 30 days in the environment.

Biosecurity measures such as limiting shared equipment and disinfection of tools and equipment that encounter an infected horse can prevent the spread of EHV. There is an EHV-1 vaccine that may reduce viral shedding of the disease, but it is not protective against the neurologic form.