How Long Can A Horse Live With EPM?

Equine Protozoal Myeloencephalitis or EPM is a deadly disease that directly attacks a horse’s nervous system.

If you’re a horse owner and are looking for preventative measures to stop EPM, you might be curious to know: How long can a horse live with EPM?

In this article, I will explore some key information about EPM, including how long a horse can live with EPM. 

So, let’s get started.

What Is EPM?

Equine Protozoal Myeloencephalitis is a serious neurological equine disease that is particularly difficult to diagnose. 

This primarily comes down to the fact that the symptoms of EPM can vary from horse to horse, and can also be very similar to a variety of other health problems.

While the symptoms are quite mild in some others, they can be severe in others. As a result, it’s important to be in tune with your horse to be able to recognize when they are behaving differently.

What Causes EPM In Horses?

EPM is caused by infection of the central nervous system with the protozoan parasites Sarcocystis neurona and Neospora hughesi.

Exposure to EPM is relatively common. In the United States, around 50% of horses have been exposed to the protozoan parasites which causes this debilitating disease.

The protozoa are spread by the host, the opossum, which acquires the organism from animals such as cats, raccoons, and skunks.

What Are The Signs Of EPM?

There are a variety of signs of EPM that are similar to other horse conditions, which is why it can be so difficult to diagnose early.

Brainstem Involvement Can Cause:

  • Behavioral changes in your horse
  • Lethargy in your horse. You might notice them lying down more often or having less energy than usual
  • Cranial nerve paralysis might manifest itself in difficulty swallowing, facial nerve paralysis, and tongue paralysis

Spinal Cord iInvolvement Can Cause:

  • Your horse to go lame or exhibit gait abnormalities
  • Ataxia or inability to control voluntary movements
  • Incoordination that might make your horse’s behavior and movement strange to usual
  • Spasticity in all four limbs, and muscle atrophy
  • Loss of balance that might cause some horses to stand with their feet splayed or lean against walls or other supports.

Symptoms may vary from horse to horse, and a horse may exhibit just one or a few of these symptoms. It’s also important to mention that signs may not be the same on both sides of the horse.

If you suspect your horse has EPM, you will need to call your veterinarian immediately. 

Is EPM Treatable?

Technically EPM is treatable, but only if it is detected early on. The success rate for treated horses is high. However, it can be fatal for many horses, as it’s difficult to detect by its early signs. 

When treated for EPM, many horses will improve and a smaller percentage will recover completely. That being said, 10-20% of cases may relapse within two years of treatment.

To give your horse the best chance, a prompt, accurate diagnosis is important and treatment should be started immediately to maximize your horse’s chance of recovery.

How long treatment can vary from horse to horse and the severity of exposure. Typically, a horse may have to take a course of FDA approved antiprotozoal drugs for about a month. However, in more serious cases, treatment might take from three to as long as nine months.

Is EPM Always Fatal?

If EPM is caught and treated early, your horse has a good chance of survival. That being said, it’s important to recognize that there are factors that can have an influence on the severity of the disease.

Speed Of Diagnosis And Treatment

The longer your horse goes without treatment, the more opportunity the parasites will have to reproduce and cause damage. This is why it’s so important to recognize the signs and seek veterinary care as soon as possible if you suspect that your horse has EPM.


How much exposure your horse is subjected to can impact how severe the EPM is. If your horse eats a large volume of contaminated feed, they are more likely to have a more severe case than a horse that has experienced light exposure.

Stress Levels

Stress can have a significant impact on the severity of the symptoms. If your horse is under a great deal of stress while infected, the symptoms and the damage will likely be much worse.


The location of the damage can impact the severity of the illness. Damage may occur at any point along the spinal cord, the brainstem or in the brain.

How To Prevent EPM

It’s important to know that all horses are susceptible to EPM. However, not all infected horses develop the disease. While there is no vaccine for EPM, there are a variety of ways to prevent EPM, including decreasing stress and reducing exposure to opossum feces.

In addition to this, you will need to make sure that you are feeding your horse a nutritionally balanced diet and are maintaining a regular schedule of veterinary visits and exams to ensure they are as healthy as possible.

To ensure that you minimize the risk of your horse succumbing to EPM, you can also take preventative measures such as:

Maintaining Separate Fresh Water Sources

Make sure that your horse has access to fresh water by frequently cleaning their tanks to avoid multiplication of harmful organisms.

Feeding Your Horses With Feeders

You will want to ensure that you feed your horse from hay nets as opposed to the dirty ground as this can contaminate your hay.

Preventing Wildlife And Vermin From Accessing Your Horse’s Food

Make sure that you keep your horse’s feed in containers with tightly-fitted lids and keep your hay storage areas locked so that vermin can’t contaminate the hay.

Properly Disposing Of Animal Carcasses

Keep vermin under control through pest services or traps. You should avoid using poisons as it’s a danger for your horse to ingest. Be sure to dispose of vermin carcasses quickly and carefully.

Clean The Area Regularly

When your horse feeds, you will want to be sure to clean up any spilled grain right away to avoid attracting vermin such as mice, rats as well as other wildlife such as possums.

Bacteria from feces and urine can build up quickly, and keeping your property clean and possum and vermin free will go far toward protecting your horse against this dangerous disease.

How Long Can A Horse Live With EPM?

There isn’t a simple answer to this question, as there are many variables that come into play such as exposure and stress levels.

As there’s no clear answer, it is absolutely imperative that as soon as you suspect or you notice any possible symptoms of EPM, you need to contact your vet immediately. As soon as you do, you should be able to get a diagnosis and begin treatment as soon as possible.

If you suspect that something isn’t quite right but hope the symptoms improve on their own, it could be fatal. It’s better to be safe than sorry, and ring your vet at your earliest opportunity if you notice that your horse is behaving differently.

Different horses respond differently to treatment. However, the faster you can get a diagnosis for your horse and begin treatment, the higher chance your horse has for recovery.

Treatment For EPM

Typically speaking, treatment to control the infection should include an FDA-approved anticoccidial drug.

Additional treatments will be provided by your vet as needed based on the severity of the signs that your horse is showing and any complicated associations as a direct result of this. 

Your veterinarian may recommend that you supplement your horse’s feed with vitamin E as an antioxidant. This comes down to the fact that Vitamin E has been known to help support healing of nervous system tissue.

The length of time that your horse requires treatment will depend on the duration and resolution of the clinical signs. 

In Summary

There’s no clear answer to how long a horse can live with EPM, as there are many variables that can affect how a horse will react to the neurological disease.

It’s important to catch the signs of EPM early on to provide your horse with the best chance of recovery. If you suspect that your horse has EPM, you will need to contact your veterinarian immediately to get a diagnosis and treatment for your horse accordingly.

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