EPM Review

EPM Review

EPM Review


Equine Protozoal Myeloencephalitis (EPM) is a serious neurological/muscle disease that can be difficult to diagnose because its signs often mimic other health problems in the horse and signs can range from mild to severe.


What is EPM?

EPM is caused by protozoal organisms known as Sarcocystis neurona and Neospora hughesi that have the ability to infect a horse’s central nervous system. It is estimated that 50-80% of horses in the United States may have been exposed to the organism that causes EPM. Given the high population of opossums in the Southwestern states (warmer climates) some veterinarians estimate there could be up to 90% exposure to EPM.  Yet, fortunately a small percentage of horses exposed to the organisms will actually develop EPM.  Sarcocystis neurona is spread by the definitive host, opossums. An opossum obtains the organism when ingesting the infected muscles from a carrier (intermediate hosts) such as cats, skunks, raccoons, armadillos, and sea otters. The infective stage of the organism (sporocysts) is passed in the opossum’s feces. A horse comes in contact with the infective sporocysts while grazing or by ingesting contaminated feed or water. A horse will not get infected from an intermediate host, however it is important to takes measures to reduce the risk from infection of EPM (Such as properly disposing of any animal carcasses on or near your property). As well as horses cannot become infected by other horses. The transmission of Neospora hughesi has yet to be identified. 

(Opossum - Definitive Host of Sarcocystis Neurona)


Signs to Look For

Signs of EPM can be slow or sudden, but can cause serious damage and lasting neurological damage when left undetected or untreated. Lesions, inflammation and pressure may develop in the brain, brain stem or spinal cord and the location of these can affect how the disease presents itself. This makes the disease difficult to diagnose with its ability to pose as other health issues, including lameness or other neurologic diseases. Horses under stress, such as that experienced by intense exercise and performance, have an increased risk of developing EPM. It is also possible for an infected horse to go without showing signs for months, years, or ever.

The American Association of Equine Practitioners has listed these EPM clinical signs to watch for: 1

  • Incoordination, weakness, abnormal gait

  • Muscle wasting/loss, usually along the topline or the hindquarters, flattening over croup area

  • Paralysis of muscles of the eyes, face or mouth, evident by drooping eyes, ears or lips (ataxia)

  • Loss of sensation of the face

  • Difficulty swallowing

  • Head tilt with poor balance; horse may assume a splay-footed stand or lean against stall walls for support.

  • Intermittent poor performance (as this is a disease often in disguise)


Diagnosis of EPM

Diagnosis is often done through ruling out other neurological diseases and performing a blood and/or cerebrospinal fluid analysis. Accurate diagnosis of EPM is challenging as there will always be false positives and negatives. To date, the most accurate EPM test is the CSF/serum ratio test, which identifies horses that are actively producing EPM antibodies within the central nervous system. Early, accurate diagnosis is key and treatment should follow immediately after. University of California (Davis) provides the most current, updated tests.


(Example of Protozoa Organism)


Treatment and Recovery

Treatment typically involves one of the following FDA- approved medications on the market: Marquis® (Bayer), Protazil® (Inter-Vet/Merck), or ReBalance® (PRN Pharmaceutical) per your veterinarian’s recommendation. The FDA also allows for compounding of some these actives to treat at a lesser cost (Approx. $250-$300) compared to the costs of these pioneer products (Approx $800-$1000). Anti-inflammatory drugs (NSAIDs) such as phenylbutazone also may be recommended to alleviate symptoms and manage pain during treatment. Although the success rate can vary, majority of veterinarians agree that the earlier treatment is introduced, the better the recovery. Horses that recover can still encounter temporary or permanent deficits. These deficits can be mild meaning the horse is able to return to riding without too much interference, yet some more serious deficits will result in a horse being retired from performance. It is estimated that up to 30% of horses treated will experience relapse, likely due to the lack of post immune support.

Supplements also should be considered a piece of the puzzle when it comes to supporting the recovery of EPM. Vitamin E is considered the most crucial anti-oxidant as it has the ability to reduce free radicals (tissue toxins) resulting from oxidative stress, by protecting the muscle/nerve cell membranes from damage. A higher dose Vitamin E is needed for specific health issues, including EPM. It is recommended to supplement approx. 5,000 to 10,000 IU of Vitamin E daily. 2


The Newest Supplement for Neurologic Health/Muscle Support

Eclipse’ PM provides several key antioxidants to promote the body's natural resistance to pathogens by helping remove damaging free radicals (tissue toxins). The high levels of B Vitamins help support normal neurological (brain/nerve) function. It also helps to support cellular health by reducing oxidative stress helping to protect body cells and tissue. Eclipse’ PM is recommended to be used in conjunction with FDA approved drug during treatments and up to 120 days post treatment (or as needed) of neurological conditions such as EPM, Lymes Disease, etc.


Highlighted Ingredients:

Vitamin E (Natural): As previously mentioned Vitamin E is considered to be the mostimportant anti-oxidant. Natural E is approx. 2.5 times more bio-available than synthetic Vitamin E (4,000 IUs Natural Vitamin E approximates 10,000 IUs of synthetic Vitamin E). Natural E is recognized to be better absorbed and pass through blood brain barrier where the disease exists.


Vitamin C (Ester C®): Powerful anti-oxidant, "free radical inhibitor" for immune support. Ester-C® is approx. 4 times more bio-available than standard Vitamin C (ascorbic acid). 1,000 mg Ester C® approximates 4,000 mg Vitamin C.


Lysine: Essential amino acid recognized to enhance a strong, healthy immune and neurological function, along with greater muscle mass/integrity.


Cinchona Bark (Herbal Extract): Recognized by scientific research to produce natural alkaloid quinine and its's impact/support role in the presence of protozoa (parasite type organisms).


Zinc, Copper, Selenium Yeast: (Trace Elements/micro-actives) identified to play key roles in triggering metabolism of other ingredients for support of healthy immune function and reducing oxidative stress from activity of "free radicals" (tissue toxins) often caused by presence of pathogens.


Selenium: (at very low levels) is highly interactive with Vitamin E and when paired together makes for a strong antioxidant.


Choline: Key active ingredient that is a part of acetylcholine (neurotransmitter) that carries messages amongst neurons, allowing the brain to inter-act/communicate with normal neurological body functions. Aids in fat metabolism in the liver and provides for cleansing of filtered tissue toxins.


B Vitamins (Riboflavin -B 2, Niacinamide B 3, Panothenic Acid B-5, Pyridoxine B 6, Folic Acid, Vitamin B12): This group of Vitamins make for support of numerous body functions and metabolism. They are in the "water soluble group" which means they float freely through/in the fluids of the body, extremely important in energy metabolism and also recognized by research for their role in healthy nerve impulses and/or if in need of neurological repair associated with neuropathy.


Tumeric (Herbal): A potent antioxidant that helps fight oxidative stress and supports overall health and well-being. The active ingredient in turmeric, curcumin, has been shown by research to help combat discomfort associated with daily exercise and aging.



Eclipse' PM



For more information regarding EPM, contact your veterinarian.


1American Association of Equine Practitioners. Horse Health, EPM: Understanding this Debilitating Disease.

2 Juliet M. Getty, PH.D. Feed Your Horse Like A Horse. Page 287.