Equine Protozoal Myeloencephalitis (EPM)

1. What is EPM?
2. How do horses get EPM?
3. What are the chances of a pregnant EPM-positive horse producing an EPM-positive foal?
4. How is EPM diagnosed?
5. Where and how can I have my horse tested?

What is EPM?

Equine protozoal myeloencephalitis (EPM) is a parasitic disease that affects horses. This neurological disease is caused by a protozoan parasite called Sarcocystis neurona. EPM is potentially fatal and is found throughout the Western hemisphere and can affect horses of any age, breed or sex. Symptoms are variable and may include muscle atrophy, asymmetry of the face, and lameness.

How do horses get EPM?

Sarcocystis spp. require two kinds of hosts in order to complete their life cycle. The first is the definitive host which is usually a species such as raccoons, skunks and opossums. Sporocysts of the organism are passed in the feces of these animals and are introduced into the water and food of prey animals. Birds and insects may help to spread the sporocysts in the environment. Normally, the parasite will undergo several cycles of development resulting in the formation of sarcocysts in the second (intermediate) host in order to continue the life cycle. When horses ingest contaminated grass or water, however, they are a dead end for the parasite. The parasite will not develop into the sarcocyst stage and will continuously cycle through an intermediate stage. These stages of the parasite are predominantly found in the cerebral spinal fluid (CSF) of the horse.

What are the chances of a pregnant EPM-positive horse producing an EPM-positive foal?

At present there is no conclusive evidence indicating that a pregnant EPM-infected mare will pass on the parasite to the fetus through the placenta - vertical transmission. This form of transmission is common for related organisms and S. neurona is currently still being investigated for vertical transmission.

How is EPM diagnosed?

The best way to determine whether a horse is EPM positive is a DNA test. The identification of DNA specific for the S. neurona organism is the basis for the DNA test used to diagnose EPM. Traditional testing involves the detection of antibodies to S. neurona in the horse's blood. Although this test is very effective and specific, it may give false positive results for horses that may have previously been infected and have already been treated and cleared of the parasite. The DNA test specifically detects whether the organism is present at the time of testing. This has the added advantage of allowing the veterinarian to monitor the treatment progress as well.

The preferred sample for testing is CSF since the organism is predominantly found there. Whole blood samples may also be submitted in a lavender top EDTA Vacutainer tube, however, accuracy of results may vary since the parasite may not be present in sufficient numbers to produce a positive result.

Where and how can I have my horse tested?

VITA-TECH Canada Inc. proudly offers the EPM DNA test at a highly competitive rate. Simply submit a completed requisition form and preferably a CSF sample in a sterile sealed container, or alternatively a whole blood sample (1-5 ml) in an lavender top EDTA Vacutainer tube labeled with the horse's name, the name of the owner or the responsible agent. Requisition forms are available upon request at no extra cost. The sample may be shipped directly to us using any two-day or next-day courier or mail service in a padded and leak-proof package. U.S. clients are asked to attach an importation permit to the package which we also provide at no extra charge.

We are proud to offer this quality service and look forward to your patronage. Our friendly, helpful staff is available to answer any questions you may have from early morning to late evening, six days a week. For inquires regarding EPM and other DNA tests or any of our other services, please do not hesitate to contact us.