Equine Protozoal

Myeloencephalitis Study9

9Bello TR, Allen TM. An Intensive Approach in the Treatment of Clinical Equine
Protozoal Myeloencephalitis. Journal of Equine Veterinary Science. 2008; 28(8):


Twenty-eight horses affected with neurologic signs due to equine protozoal myeloencephalitis (EPM) were treated with a triple therapy of ponazuril, transfer factor, and MicroLactin®. Ponazuril provided antiparasitic therapy, transfer factor stimulated cell-mediated immunity, and MicroLactin inhibited inflammatory reactions. After treatment, 82% (23/28) of the horses were able to return to work.

Many experts consider EPM as “a serious parasitic disease with neurologic consequences” instead of a “serious neurologic disease caused by a parasite.” The study’s authors wanted to address the host-parasite immunologic reactions associated with the disease by including ponazuril, transfer factor, and MicroLactin in the treatment protocol. Ponazuril is an antiparasitic. Transfer factor contains dialyzable leukocyte extracts that can transfer and stimulate cell-mediated immunity, which is important in controlling intracellular parasites. MicroLactin protects against destructive inflammatory reactions.

Objective: Utilize a triple therapy of ponazuril, transfer factor, and MicroLactin to combat the parasitic, immunologic, and inflammatory components of equine protozoal myeloencephalitis (EPM) in order rehabilitate equine athletes.

Materials & Methods

Twenty-eight horses with clinical signs of EPM—such as gait abnormalities (stumbling), behavior changes, weakness, and asymmetrical muscle loss—exhibited positive serum immunoblot tests to confirm exposure to Sarcocystis neurona. A presumptive diagnosis of EPM was made based on clinical signs, a positive serum immuoblot test, and physical examinations; a confirmatory cerebral spinal fluid analysis was not performed. Nine breeds were represented in the study with ages ranging from 3-20 years. There were 15 geldings and 13 mares.

Transfer factor (750 mg twice daily for 7 days, then once daily for 30 days) was fed for a total of 37 days, while both MicroLactin® (7,000 mg twice daily) and ponazuril (5 mg/kg once daily) were given for 28 days. Five horses were treated with ponazuril and transfer factor, and the remaining 23 were treated with a triple therapy of ponazuril, transfer factor, and MicroLactin. Fifteen horses required an extended course of medication.

Results & Discussion

After treatment, 82% (23/28) of the horses were able to return to work. Eighteen of these returned to their previous activity or were sold as athletes, while five of these horses remained in physical rehabilitation but were able to do controlled exercise under saddle.

Five acutely affected horses were not helped by the therapy. Two of these horses were deemed unsafe and were euthanized within 60 days. The final three made improvements but remained unsafe to ride and were euthanized within 6-24 months of therapy. A treatment crisis occurred in one horse that received only transfer factor and ponazuril.


Treatment of EPM with ponazuril alone has an expected improvement rate of 60%, with only 10-20% of horses making a complete recovery.10 With the addition of transfer factor to promote cell-mediated immunity and MicroLactin to inhibit exuberant inflammation, 82% of horses improved, with 64% making a full recovery. The study’s authors “considered transfer factor, MicroLactin, and ponazuril to be equal partners attacking the clinical challenge from different, but specific, directions.” Although this study was not placebo-controlled, it suggests an improved treatment response for EPM with the described triple therapy.

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