Equine protozoal myeloencephalitis (EPM) is a frustrating disease. It’s been referred to as one of the most overdiagnosed, underdiagnosed and misdiagnosed equine diseases – an apt description. In some areas, every horse (particularly every racehorse) that has any real or perceived abnormality (such as not running fast enough) gets treated, usually without any attempt to make a true diagnosis. Most of these animals don’t have EPM, but some might, along with horses displaying a range of sometimes vague neurological signs. When an effort is made to really establish a diagnosis, unfortunately it’s not straightforward, which leads to more confusion about the disease and how to manage it.

The Animal Health Diagnostic Center at Cornell University have released a document on EPM testing and diagnosis. This document discusses when and why to test, along with important information about the available, recommended tests. It’s a nice, comprehensive overview of the subject and worth a look for equine veterinarians as well as horse owners wondering whether their horse may have this enigmatic disease.