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c23aa0c5320c9acbda08ddf7ab6dd4e0EPM is an overwhelming topic because the literature isn’t often clear and easy to find.  New information is especially important. We provide consulting as an adjunct to the veterinarian helping bring a horse back to use.

Our consulting is data driven.  Serum, and sometimes CSF testing, forms the basis for our analysis. Infection with and exposure to S. neurona organisms are detected by serum tests. Sarcocystis neurona is the organism that can sometimes, rarely, get into the brain of horses.  We developed tests identifying toxin-producing muscle cysts caused by Sarcocystis fayeri .   Fayeri causes signs that make horses look like they have EPM.  Most important, we developed serum tests that detect inflammation.  Inflammation is part of the immune response to parasitic infections in horses.  Inflammation can become dysregulated .  Unregulated inflammation can lead to life-ending disease.  It is critical to treat uncontrolled inflammation  with drugs that target the disease process and that is why testing is important.  Identify and treat for the treatable.

EPM is a disease of inflammation and infection.  By definition, EPM requires that S. neurona is in the brain of horses. All serum and CSF tests for  “EPM”  detect antibody against S. neurona.  Non-specific tests pick up other protozoa as well. These organisms do not cause EPM.  Importantly, NO TEST WILL TELL YOU THAT THERE ARE S NEURONA ORGANISMS IN THE BRAIN! Some tests give you a “percent chance” that the horse looks like “x-number” of horses that did have EPM isolated from brain tissue.  This is not the same thing as a diagnosis of EPM!  The “x”, the number of horses used to evaluate tests, is published. It can be as few as nine.  Bottom line here is that there are no EPM tests. Useful tests do exist and can take the mystery out of treating the horse with EPM.

Sarcocystis neurona  tests measure antibodies that identify this organism (or in non-specific tests, some other protozoa are identified as well). A horse that is exposed to S. neurona  produces antibodies. Controlled, blinded, challenge studies showed  that antibody levels were unrelated to the presence of  organisms in the brain.  In one study it was statistically significant that antibody increases with the duration of infection.  Importantly, the antibody levels change with infection that is influenced by the history of the horse's prior exposure or infection, that is the  immune background.  No prior exposure means the horse is naive. After a horse has the first infection, it is now "experienced". It takes up to 7 months for antibodies to decrease in an “experienced” horse.  With each exposure, the antibody level will go higher and last longer.

Seventy eight percent of normal horses in the United States have antibodies against S. neurona!  Twenty four percent of clinically normal horses have antibody against a toxin from muscle cysts due to S. fayeri-sarcocystosis! When the organism is in the environment and a horse ingests the infective stage, antibodies are produced and they hang around a long time. Antibodies can cross the blood brain barrier for both S. neurona and S. fayeri.  Finding S. neurona antibodies in the CSF doesn’t guarantee the organism is in the brain tissues. The serum/CSF ratio is a calculation used by some laboratories to adjust for high serum antibody levels.  It is also suggested that this ratio changes with the population being tested.  Call us to review the literature on this topic.

Inflammation has been a back burner issue in EPM research for 30 years.  We propose that inflammation is an important consideration to diagnose disease.  Treating inflammation is critical for management of horses with neuromuscular disease. Do you know why?

Our consulting service provides guidance for veterinarians faced with horses suffering from neurodegenerative disease.  We concentrate on the diseases  “EPM”,  equine muscular sarcocystosis (EMS), sub-clinical inflammation after EPM treatment, and polyneuritis equi.  Horses with a presumptive EPM diagnosis benefit from testing.  We guide the veterinarian to the next steps in treatment options and further testing.

Contact us for a consult today!  Not sure if a consult is necessary?  We are happy to let you know what services are appropriate to each horse. We can increase your EPM IQ!

Equine Protozoal Myeloencephalitis has many presentations.  Horses can be ataxic, lame, or stumble.  Some horses have behavior changes.  And some horses may have trouble eating (dysphagia), show abnormal airway function, or even have seizures. Vital signs are usually normal and can have muscle atrophy.  A horse with suspect EPM may or may not have active protozoal infection.  It is likely the clinical signs are due to inflammation, a part of the disease syndrome.  Some horses may look like they get repeat infections, although this can be due to chronic inflammation.

The first “test” is done by a veterinarian, it is the neurologic examination.  Signs can include gait deficits, we call the exam a GAIT ASSESSMENT SCORE, GAS, the horse has a number value between 0 to 5.  Clinical signs can include behavior issues or cranial nerve deficits without an abnormal gait.  These horses receive a GAS of 1.

The next tests analyze for antibodies in serum and/or CSF. ELISA Submission Form EPM Chart

There are several antibody tests, pathogen specific tests are the SAG 1, 5, 6 ELISA.  These proteins define a serotype of the S. neurona that infected the horse. Horses can have multiple exposures.  A positive test is suggestive that the signs are due to S. neurona. The tests can be used to test antibodies present cerebrospinal fluid (CSF). We produced a video for a standing procedure for CSF collection, an experienced veterinarian can collect the fluid in a matter of minutes.

An important part of the analysis of serum is the level of C-reactive protein.  This is a measure of the inflammation, An elevated CRP that doesn’t decrease after treatment indicates a chronic condition.

A response to treatment is often used by a field veterinarian to help diagnose EPM.  If a horse has not been treated in the last 90 days it is considered untreated.  If there are protozoa present an antiprotozoal treatment is indicated. If there is no response to treatment in 14 days the treatment is considered a failure. A partial response to treatment may mean the horse has post-treatment EPM syndrome.

There are additional tests to run if a horse fails on treatment.  A serum test for S. fayeri is appropriate, especially if there is muscle wasting or loss.  A significantly elevated CRP value (>39) may indicate polyneuritis.  The MP2/MPP test can determine if there are antibodies against myelin protein.  This is an important distinction because treatment is different than those used for horses with EPM. If there is a partial response to treatment a change in CRP is a good indicator of treatment effect.

Lyme disease is also considered when horses are exposed to ticks that carry Borrelia.  Our screening test is used to determine if Lyme should be considered in horses entering the field trial. If the screen test is 40, positive, confirmatory testing or treatment is indicated.

A horse with a diagnosis of chronic EPM, also known as relapsing/remitting EPM, should be tested for MP2/MPP and CRP.  The CRP value is an indicator of sub-clinical disease and can be used in evaluating the end of treatment in autoimmune polyneuritis.

Here is a link to our testing options.  Pathogenes Testing Options