Equine Protozoal Myeloencephalitis– A Comparison of Western Blot Results for Serum and Cerebral Spinal Fluid With Postmortem Findings in Normal and Neurologic Horses

The western blot (WB) for S. neurona performed on serum and spinal fluid (CSF) is widely used for antemortem diagnosis of neurologic disease and for screening normal horses. Because CSF collection is difficult, the WB is often performed on the more readily available serum sample only. However, seroprevalence to S. neurona is high in normal horses and studies to evaluate the blood test have not been reported. There are difficulties with interpretation of positive CSF WB results. The test detects minute amounts of antibody to S. neurona so that slight contamination of the CSF with blood can result in false positive readings in seropositive horses. In addition, breach of blood-brain barrier and cross reactivity with other protozoa may give false positive results. 3 The purpose of this work was to reassess the value of the WB for both serum and CSF and to evaluate the usefulness of the WB in normal horses.