What Are The Signs Of EPM In Horses?

Last Updated on July 20, 2022 by admin

As a horse owner or carer, being able to recognize the signs of EPM in horses can help you spot this challenging disease. EPM is a complex neurological disorder of horses that is, unfortunately, becoming more commonplace. Let’s find out everything you need to know about EPM in horses!

What Is EPM In Horses?

Equine Protozoal Myeloencephalitis (EPM) is a neurological disease of horses, caused by the protozoal parasite Sarcocystis neurona. This parasite cannot be transmitted from horse to horse but is spread by the opossum. The opossum sheds infected sporocysts, which the horse then consumes when grazing or eating contaminated feed, or drinking contaminated water.

When the parasite enters the digestive tract, it then migrates into the bloodstream and is able to cross the blood/brain barrier. Here it can attack the central nervous system, causing significant neurological problems.

It is thought that over half the horse population in the US have been exposed to the parasite that causes EPM. Some show only mild symptoms, while others develop severe neurological disease. The rate of onset of the disease is variable – in some cases it is rapid, whilst in others, it can be slow and subtle.

Read more about What Surrounds The Cauda Equina?

What Are The Signs OF EPM In Horses?

The problem with EPM in horses is that the clinical signs mimic many other neurological diseases of horses. The symptoms range from mild to severe and can fluctuate widely. However, one key difference is the signs of EPM in horses are not normally symmetrical, and one side of the body is normally more affected than the other.

The signs of EPM in horses vary according to the location of the lesions in the central nervous system, as well as their severity. These may include:

  • Incoordination, stiffness, lameness, or an abnormal gait
  • Weakness, particularly when going up or down inclines
  • Muscle loss over the topline and hind quarters
  • Paralysis of facial muscles, causing drooping of the ears, eyes, or lips
  • Difficulty swallowing food, water, or saliva
  • Abnormal or patchy sweating
  • Reduced skin sensation on the face, neck, or body
  • Poor balance; the horse may lean against walls for support, or stand with the legs splayed outwards
  • Head tilt
  • Seizures or collapse

Some horses are only mildly affected by EPM and the symptoms develop slowly, while others show severe clinical disease very rapidly. Some factors appear to be linked to the severity and speed of progression of EPM in horses:

  • The quantity of disease-causing parasites that are ingested
  • How quickly treatment is initiated
  • The location in the central nervous system where the parasite is concentrated
  • Events that cause increased stress following EPM infection

2018 Researching EPM: Polyneuritis equi Explained

Signs Of EPM In Horses

It is clear to see that a rapid diagnosis and treatment for horses with EPM is essential to maximize the chances of a full and fast recovery. If EPM is not diagnosed and treated, it can cause lasting and irreversible neurological damage to the horse.

What Is The Treatment For EPM In Horses?

A rapid diagnosis of EPM is essential to prevent irreversible neurological damage to the horse. Your veterinarian will carry out diagnostic tests to confirm a diagnosis of EPM and a full neurological examination. The tests include routine blood analysis, as well as collecting a sample of cerebrospinal fluid from the spinal cord.

Around two-thirds of horses with EPM make a full recovery with rapid and aggressive treatment. Your veterinarian will prescribe a course of anti-protozoal medication to kill the parasite that is attacking the central nervous system. While this is taking effect, other medications such as anti-inflammatories will be administered to ease discomfort and alleviate symptoms.

The anti-protozoal treatment can take up to six months, depending on which medication is administered. During this time, supplementation with vitamin E can help the central nervous system tissues to heal. Treatment for EPM in horses can be expensive and prolonged, and not all horses will make a full recovery. 10 to 20 percent of horses may relapse when treatment is stopped.

Whilst treatment for EPM is taking place, your veterinarian may take regular blood samples to assess the response to treatment. The medication used to treat EPM in horse can cause anaemia, so this should also be tested for regularly.

What Is The Treatment For EPM In Horses

Summary – Signs Of EPM In Horses

So, as we have learned, the signs of EPM in horses include neurological symptoms such as reduced skin sensation, patchy sweating, and an abnormal gait. The signs of EPM in horses are not normally symmetrical, and one side of the body is normally more affected than the other. Rapid diagnosis and treatment for horses with EPM is essential to maximize the chances of a full and fast recovery.

We’d love to hear your thoughts on the signs of EPM in horses! Have you ever owned a horse that was diagnosed with this challenging condition? Or maybe you’ve got some questions about the best way to care for a horse with EPM? Leave a comment below and we’ll get back to you!


How Do You Test For EPM In Horses?

Two tests are used to diagnose EPM in horses. A blood test can be taken which will identify if the horse has been exposed to the parasite that causes EPM, but cannot show if the infection is current or historical. A sample of spinal fluid can help to confirm a diagnosis of EPM.

Are Horses In Pain With EPM?

Horses with EPM often suffer with pain around the poll, the area at the top of the spine behind the ears. This is due to inflammation and pressure within the spinal cord.

Can A Horse Recover From EPM?

Most horses with EPM will make a full recovery if treatment is initiated promptly and aggressively. If left untreated, EPM can cause long-lasting and irreversible neurological damage.

What Should I Feed My Horse With EPM?

Horses with EPM benefit from a diet that is high in fiber and fat, and low in starch. Vitamin E and folic acid can help to aid healing of the damaged nerve tissues. Many horses with EPM suffer from weigh loss, so a nutrient rich and highly palatable diet should be fed.