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Equine Protozoal Myeloencephalitis (EPM)


Equine protozoal myeloencephalitis (EPM) is a progressive, degenerative neurological disease of the central nervous system and is one of the most commonly diagnosed neurological disorders of horses in the United States. It is usually caused by the organism Sarcocystis neurona, and can be difficult to diagnose definitively as many horses have been exposed and carry a titer, but remain normal. In recent times, Lyme disease with neurologic symptoms has been confused with EPM. Many natural compounds can enhance the immune system which helps in the treatment




The EPM protozoa parasite does not occur in horse manure; so the disorder is not spread between equines. Owners can make a difference by learning effective prevention measures and how to identify EPM symptoms right away. If EPM is diagnosed and treated early, many horses with the disorder respond well to treatment, with a good percentage recovering fully.  



If EPM is suspected, careful veterinary examination, including blood or spinal fluid tests must be done to rule out diseases like West Nile Virus or viral encephalitis. Laboratory testing for EPM is not definitive, though some of the new tests are more accurate than in the past. Once a diagnosis of EPM is established, treatment of the horse should start immediately.  A delay in treatment allows the disease to progress, potentially causing additional permanent damage to the central nervous system.  


Treatment can involve drugs known to kill or retard the reproduction of the responsible protozoa S. neurona.  None of the drugs kill 100% of the protozoa. But the drugs reduce the protozoa population to a level where the horse's immune system kills the rest.  It is important to help the equine rebuild its immune system while treatment is ongoing. Relapses are frequent without strong immune system support. Reduction of stress and a healthy diet are also important. Significant help is also needed through supplementation in supporting the immune system in order to combat this disease.



Treatments can be expensive. Although complications are rare, treatments may affect stallion fertility and may pose certain health risks to unborn foals. While treatment success rates are high, not all equines respond positively to therapy and approximately 10-20% of horses may experience a relapse. Equines that have recovered may still suffer from some permanent damage.


While a horse is being treated, taking intermittent blood samples may be recommended to monitor potential side effects such as anemia, low platelet count and low white blood cell count. Some drugs used to treat EPM are antifolate drugs (drugs which impair the proper folic acid metabolism often producing a folic acid deficiency). Therefore, periodic examination for anemia is recommended during treatment. 

Equines undergoing treatment should also be closely observed for signs of decline, particularly from the negative side effects of the administered drugs, such as acute diarrhea. 



Integrative Medicine


The following nutraceuticals or natural/herbal formulas can also provide effective treatment and support for equines living with EPM.


In addition to the drugs administered, there are many alternative therapies to help horses recover from EPM. These include acupuncture, Chinese herbs, chiropractic treatment, massage and vitamin therapy and traditional herbs.


Natural products like herbs can help an EPM horse to recover from the stress it often undergoes during the first three months of conventional treatment, such as heavy drug therapies like sulfa drugs. Herbs can be used during this time for "whole body support" while strengthening the equine’s immune system. Examples of the herbs include:


» Astragalus;

» Siberian Ginseng;

» Feverfew;

» Nettle;

» Yarrow;

» Cleavers;

» Dandelion leaf;

» Calendula; and

» Boneset.


Pau D'arco tree bark has also been found to have anti-protozoan properties as well as being able to boost the immune system. Other herbs such as Milk Thistle and Dandelion help liver function and prevent some of the toxic side effects of the drugs. If the EPM horse is anemic, Chinese blood-building herbs can be used in conjunction with the drugs.


Equine Protozoal Myeloencephalitis: EPM
(Reference: Veterinarians’ Desk Reference)

(Live Link)


Background: EPM occurs in most parts of the country and ranges from mild to severe. Conventional treatments are expensive, long-term and debilitate the immune system. Recurrences or relapses are common.

Symptoms: Debility, ataxia and uncoordination; symptoms vary from very mild and non-specific musculoskeletal soreness to severe ataxia.

Diagnostics: Early diagnosis is of utmost importance.

Special Notes: The causative organism becomes problematic within the body when the immune system is depleted due to stress, inadequate nutrition or excesses or deficiencies in the diet. Relapses are frequent without immune system support. Reduction of stress and a healthy diet are also important.

Principles for Supplementation: Need significant help in supporting the immune system in order to combat this disease.








2 scoops bid

Source of naturally occurring bioactive proteins–IGG and peptides, modulates gut barrier function and inflammatory cytokine production, and improves immunity.


12-24 capsules sid

Includes the best-researched nutrients for neurological support, providing antioxidant protection for sensitive neuronal tissue.


1 scoop bid

Component of acetylcholine.

Enhance Life14

4 tsp bid

Helps the overall metabolism of older horses, improves weight and energy level.


8-12 capsules sid

Strengthens immune system.


2-5 mL, bid or tid

Corrects intestinal pH; supports intestinal healing during antibiotic use.


4-10 capsules sid

Balanced forms of Vitamin E. No added soy oil (a pro-oxidant). Antioxidant. Vitamin E deficiency can occur with commonly used drugs.

ABC’s EPM Supplement w/o folic acid1

1 scoop sid

Contains Vitamin E, Choline, antioxidants for nervous system support.


6-10 mL sid
Adapt to stress.

Adaptogenic herbs, support the immune system, adrenals, reduces stress, helps horses

Qing Hao San3

2 scoops bid

Tonifies Qi, kills parasites, strengthens nervous system.


To help you quickly find the right Integrative Medicine formulas and manufacturers to help treat your dogs, cats and horses, please refer to the Veterinarians’ Desk Reference
(Click Here)




Prevention is critical in controlling EPM development.  Here are some immediate steps equine owners can take in helping to control or eliminate EPM:


» Limiting opossum access to the barn or stable and pasture is the best preventative measure. Opossums are good climbers and may enter the barn over a stall door. 


» Pick up all cat and dog food every night and store it in a raccoon/opossum proof container.  


» Sweep up spilled grain immediately and empty the trash can often. 


»  Keeping food items locked up or out of the barn will make it less tempting for opossums to enter.


» Trapping and relocating opossums as well as installing appropriate fencing can also help prevent against your equines being exposed to EPM.




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