Dr. Joseph Bertone is a member of the Idaho Equine Hospital. He is board certified in Large Animal Medicine and has published and presented information in the areas of shock, physiology and neurology. He is a renowned speaker in the area of equine internal medicine.

Dr. Bertone presented an overview of equine neurology and the diseases associated with the neurologic system. Equine Protozoal Myeloencephalitis (EPM) a devastating neurologic disease caused by a protozoan organism (Sarcocystis neurona) was discussed in depth. EPM affects all breeds of horses, but is more commonly reported in Standardbreds and Thoroughbreds. There is no age restriction; however, the disease appears to affect younger horses (average age is 4 years), typically when competing or racing. The disease often presents as an asymmetrical gait deficit, which may be confused with lameness. Dr. Bertone discussed the neurologic examination and special tests that can be conducted to differentiate EPM from other types of neurologic disease and lameness. EPM is treatable, but often times not curable as the residual damage in the central nervous system is often irreversible. Standard treatment is long-term administration of a combination of a sulfonamide antimicrobial drug and pyrimethamine. Although this combination is not approved for treatment of EPM, extensive research is underway to determine the effectiveness of this combination and several other pharmacologic agents such as diclazuril (Clinacox), toltrazuril (Baycox) and nitazoxanide.

Dr. Bertone also discussed the procedure for collection of cerebrospinal fluid (CSF), necessary to diagnose EPM. Collection of CSF requires a 8-inch needle, proper restraint and sedation and correct anatomic placement of the needle. CSF fluid is subjected to a test named the Western Immunoblot test to determine if antibodies to the protozoan are present. Detection of antibodies in the CSF is somewhat problematic in that blood contamination, either from the introduction of the needle during the procedure, or from trauma to the spinal cord or brain, may result in a false positive test result. It has been shown that up to 45 percent of the normal horse population has been exposed to the organism and carries antibodies in the blood. Only those that have antibodies in the blood and in the CSF are considered to have active disease. Two tests, the albumin quotient and the IgG index have been developed to help rule out the blood contamination as the cause for a positive test result. It is now known that a very small amount of blood contamination may result in a positive test. Research is underway in this area to refine the Western Immunoblot test. Dr. Bertone also presented videotapes of neurologic horses and discussed the neurologic examination as the horse was being examined.

Credits: US Food and Drug Administration