Current EPM Rates Show Better Diagnostic, Treatment Options

Data suggest that veterinarians are treating EPM in the field and referring fewer cases.

No account yet? Register


Current EPM Rates Show Better Diagnostic, Treatment Options
Ninety-seven percent of surveyed practitioners performed a neurologic exam in the EPM cases. | Photo: Stephanie L. Church/The Horse
Back in 2010, equine researchers combed through 17 years of records from 15 veterinary teaching hospitals to determine if equine protozoal encephalomyelitis (EPM) case numbers were rising, dropping, or staying steady over time. They also conducted a survey of equine practitioners to get their perspective on incidence of this debilitating neurologic disorder.

At the time, EPM caseloads were steady and practitioners perceived they were dropping or staying the same in their practices. Seven years, more specific diagnostics, and an additional EPM treatment product later, what’s the picture? The research team wanted to find out.

Frank Andrews, DVM, MS, Dipl. ACVIM (LAIM), LVMA Equine Committee Professor of Internal Medicine and Director of the Equine Health Studies Program at Louisiana State University School of Veterinary Medicine, in Baton Rouge, and colleagues at the University of Tennessee College of Veterinary Medicine and the Virginia Maryland Regional College of Veterinary Medicine picked the study methods back up, looking at data from 1990-2015, and surveying veterinarians in the early part of 2016. Andrews presented the team’s research results at the Second EPM Society Workshop, held Oct. 25-27, 2017 in Tahoe City, California.

“What we wanted to do in this particular study was to calculate the proportional morbidity rate (PMR), which is an indicator of incidence in a population of horses for EPM … that were presented to the veterinary medical teaching hospital over a period of time,” he said. Incidence is the number of new cases of a specific diagnosis in a specific population during a specific period, divided by the total number of all diagnosed cases in that same population. So, in this study, it would be the number of EPM cases among all the veterinary teaching hospitals 1990-2015 divided by the total caseload (excluding field service cases and well-animal checks).

Eighteen and nine veterinary colleges reported their EPM numbers to the Veterinary Medical Data Base (VMDB) from 1990-2006 and 2007 to 2016, respectively, and total caseload counts over that time. Andrews reported those teaching hospitals made 2,111 diagnoses of EPM from 263,862 accessions. So, the overall PMR was 0.8% in 25 years, he said, and probably underestimated based on population

Create a free account with to view this content. is home to thousands of free articles about horse health care. In order to access some of our exclusive free content, you must be signed into

Start your free account today!

Already have an account?
and continue reading.


Written by:

Stephanie L. Church, Editorial Director, grew up riding and caring for her family’s horses in Central Virginia and received a B.A. in journalism and equestrian studies from Averett University. She joined The Horse in 1999 and has led the editorial team since 2010. A 4-H and Pony Club graduate, she enjoys dressage, eventing, and trail riding with her former graded-stakes-winning Thoroughbred gelding, It Happened Again (“Happy”). Stephanie and Happy are based in Lexington, Kentucky.

Related Articles

Stay on top of the most recent Horse Health news with

FREE weekly newsletters from

Sponsored Content

Weekly Poll

sponsored by:

When do you begin to prepare/stock up on products/purchase products for these skin issues?
85 votes · 85 answers

Readers’ Most Popular

Sign In

Don’t have an account? Register for a FREE account here.

Need to update your account?

You need to be logged in to fill out this form

Create a free account with!