EPM: The Next Step(s)

EPM research is proceeding at a fast pace across the country, as you will see in our EPM Special Report this month. There are many questions to be answered, and many of those answers result in more questions. Here are some of the knowns, and the unknowns.

It is known that many horses are exposed to the parasite that causes EPM and thus develop antibodies against the parasite (50-100% of some populations), but only 0.5-1.0% of horses with antibodies actually show signs of the disease. Why? It is thought that the immune system somehow is compromised in sick animals, but what are the contributing factors and how can they be combatted?

Prior to The Ohio State breakthrough that solved the life cycle of Sarcocystis neurona (the parasite that causes EPM) in the lab, there was no way to consistently give horses the disease in an experimental setting. The current model of the life cycle needs to be refined, which will allow scientific testing and verification of treatments, preventatives, and vaccines. In other words, scientists (and horse owners) will be able to find out if something that claims to work actually does work.

No matter how many tests are done in cell culture or in specially bred mice, products still have to be tested on horses. For each treatment, for example, we need to know if a medication is absorbed by the horse, if it attacks and kills the parasite, its side effects, and the duration of treatment. This information must be passed to veterinarians and the industry so we don't create "resistant" parasites by improper treatment--which has happened! But, don't think the "knockout mice" tests aren't serving a purpose. Using specially bred mice with a specific aspect of their immune system altered could give insight as to what might be compromised in the horse immune system.

The Western blot test is extremely useful in determining if a horse does not have antibodies for S. neurona. However, if a horse tests positive, we need additional diagnostic tests to determine if he is merely exposed, or whether he has the disease (even before the onset of clinical signs).

The cat can be used in the laboratory to complete the life cycle of S. neurona, but is the cat the "natural" intermediate host, one of several intermediate hosts, or just a laboratory substitute? (Remember, live cats pose no risk for horses; it's only if the cat is infected, dies, and is eaten by an opossum that it could potentially pass the parasite to complete the life cycle.)

Can a vaccine against EPM work? Can prophylactic treatments work? Can horse owners afford these treatments?

To answer these questions and many more, EPM research requires horses. The spinal cord, brain, and tissues of experimental horses must be examined to make the best use of each horse's sacrifice to EPM research. Teamwork is essential.

Research requires money. The speed of solving this problem now is directly related to the amount of money available to conduct research. There is room immediately for at least another $1 million in research funding. Where will researchers find those dollars, and how will they be divided?

There are more specific questions that are being and will be studied, but in order to solve the problem of EPM, we need to address the last ones first.

Monies, Funding, Grants

Whatever you want to call it, researchers need dollars. They can only do the work they can afford to do, no matter how many educated, experienced, dedicated, and eager people there are to solve the problem.

Someone might have a great idea for determining what triggers a horse's immune system to slow down, thus allowing the S. neurona parasite to flourish and cause disease in a previously healthy horse. This research must involve a "double blind study," which has control horses to compare with the ones in the experiment. Horses must not have antibodies to EPM before the experiment. They must be housed in a place that prevents incidental/accidental exposure (whether through opossums, mice, birds, insects, or any other potential carrier). There must be enough horses in the experiment to make the outcome statistically significant. There must be a myriad of specialists involved--from the clinician who determines if a horse has neurologic signs, to the parasitologist who knows the life cycle, to the epidemiologist who determines if something is significant in the population, to the laboratory helpers who care for the animals.

And that doesn't include the high-tech machines, computers, and facilities needed to conduct the laboratory portion of the research!

Here is my challenge: That each one of us who has a concern about EPM send whatever your conscience deems appropriate to research. If you don't have a favorite university, I recommend the Grayson-Jockey Club Research Foundation. Each year, that group gives more money for equine research than any other foundation. They already have spent nearly $300,000 on EPM research. This is a group with veterinarians, researchers, practitioners, and academicians who have knowledge of what is important to horse owners, and the validity of requests for each dollar. The Grayson-Jockey Club Research Foundation is a 501(c)(3) not-for-profit entity, which means your contributions are tax-deductible. Their address is: Grayson-Jockey Club Research Foundation, 821 Corporate Drive, Lexington, Ky. 40503; 859/224-2850; http://home.jockeyclub.com/grayson.html.

The right people are willing to work toward solving EPM, but without funding, they sit idle.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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