what is epm in horses

3 min read 18-03-2025

Meta Description: Equine protozoal myeloencephalitis (EPM) is a debilitating neurological disease affecting horses. Learn about its causes, symptoms, diagnosis, treatment, and prevention in this comprehensive guide. Understand how this parasitic infection impacts a horse's neurological function and explore the latest advancements in managing EPM.

What is EPM in Horses?

Equine protozoal myeloencephalitis (EPM) is a neurologic disease affecting horses. It's caused by infection with the parasite Sarcocystis neurona. This parasite can lead to significant and sometimes irreversible neurological dysfunction. Understanding EPM is crucial for horse owners and veterinary professionals alike.

Understanding the Sarcocystis neurona Parasite

Sarcocystis neurona is a single-celled parasite that primarily infects opossums. Opossums act as the definitive host, meaning the parasite sexually reproduces within them. Horses become infected by ingesting food or water contaminated with opossum feces containing the parasite's spores. While opossums are the primary reservoir, other animals, including raccoons and armadillos, can also carry the parasite.

How Horses Contract EPM

The transmission of Sarcocystis neurona to horses is indirect. It doesn't involve direct contact with opossums. Instead, horses are infected through ingestion of contaminated material:

Contaminated feed or water: The most common route of infection. Spores can survive in the environment for extended periods.
Insect vectors: Some insects may carry the parasite and potentially transmit it through bites.

The parasite then migrates to the horse's brain and spinal cord, causing inflammation and neurological damage.

Recognizing the Symptoms of EPM

EPM's symptoms vary greatly, depending on the severity and location of the neurological damage. This variability makes diagnosis challenging. Common signs include:

Ataxia: Loss of coordination, often presenting as a swaying gait or stumbling.
Muscle atrophy: Wasting away of muscle tissue, particularly in the hindquarters.
Weakness: General weakness, particularly in the hind limbs.
Swayback: An abnormally curved back.
Head tilt: The horse's head may be tilted to one side.
Difficulty swallowing: Dysphagia can lead to weight loss and aspiration pneumonia.
Behavioral changes: Changes in temperament, such as increased aggression or lethargy.

Subtle Symptoms:

It's vital to note that EPM can present with very subtle symptoms. These might include:

Decreased performance: A horse may show reduced athletic ability without exhibiting obvious lameness or gait abnormalities.
Difficulty turning: Turning might seem stiff or awkward.
Changes in gait: Slight alterations in the horse's stride or foot placement.

Any subtle or unusual changes in your horse's behavior or performance should prompt a veterinary examination.

Diagnosing EPM

Diagnosing EPM can be difficult due to the variability of symptoms and the lack of a single definitive test. Veterinarians typically use a combination of methods:

Clinical examination: A thorough neurological exam to assess the horse's coordination, muscle strength, and reflexes.
Blood tests: While not conclusive, blood tests can detect antibodies to Sarcocystis neurona.
CSF analysis: Cerebrospinal fluid (CSF) analysis may reveal the presence of the parasite or inflammatory markers.
Imaging techniques: MRI or CT scans can help identify lesions in the brain and spinal cord.

Treating EPM

Treatment for EPM typically involves the use of antiprotozoal medications, primarily:

Diclazuril: A commonly used drug that targets the parasite.
Ponazuril: Another effective antiprotozoal drug.

Treatment duration varies, often lasting several months. The goal is to reduce the parasite load and mitigate neurological damage. However, complete recovery isn't always guaranteed, and some horses may have permanent neurological deficits.

Supportive Care:

Beyond medication, supportive care is crucial for horses with EPM. This may include:

Physical therapy: To improve muscle strength and coordination.
Nutritional support: A balanced diet to maintain weight and overall health.
Regular veterinary checkups: To monitor progress and adjust treatment as needed.

Preventing EPM

Preventing EPM is challenging, as it's difficult to eliminate opossums from the environment. However, you can reduce the risk of infection by:

Controlling opossum populations: While complete eradication is unrealistic, measures to deter opossums from areas where horses are kept can help.
Proper sanitation: Maintaining clean stalls, pastures, and water sources to minimize parasite contamination.
Careful feed management: Storing feed in sealed containers to prevent contamination.
Regular veterinary care: Routine checkups can help identify early signs of neurological problems.

Living with EPM

EPM's prognosis varies. Some horses recover fully with treatment, while others experience lasting neurological deficits. The severity of the infection, the horse's age, and the response to treatment influence the outlook. Close monitoring and supportive care are essential for horses with EPM.

Conclusion

EPM is a significant neurological disease affecting horses. Early recognition of symptoms, prompt veterinary diagnosis, and appropriate treatment are vital for managing the condition. While a cure isn't always possible, effective management strategies can improve the quality of life for horses with EPM. Remember to consult your veterinarian for any concerns about your horse's health. They can provide personalized guidance and support based on your horse's individual needs.