Two Common Acute Phase Proteins Not So Helpful for EPM Diagnosis

Two research teams investigated whether APPs could serve as EPM markers and came to similar conclusions.
Please login

No account yet? Register

Pulling Blood
EPM is difficult to confirm with bloodtests because many horses have been exposed to Sarcocystis neurona, one of EPM’s causative parasites and, so, have blood serum antibodies against the pathogen. | Photo: Erica Larson, News Editor

The neurologic disease equine protozoal myeloencephalitis (EPM) is notoriously difficult to confirm with bloodtests. This is because many horses have been exposed to Sarcocystis neurona, one of EPM’s causative parasites and, so, have blood serum antibodies against the pathogen. Also, there’s no such thing as a “textbook” EPM case, as far as clinical signs go, and a variety of conditions besides S. neurona infection can cause neurologic illness, complicating the diagnostic picture.

These limitations mean veterinarians are always looking for adjunct tests to add to their diagnostic arsenal. Recently, in two separate studies, Amy Johnson, DVM, Dipl. ACVIM, of the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center, in Kennett Square, and Steve Reed, DVM, Dipl. ACVIM, of Rood & Riddle Equine Hospital in Lexington, Kentucky, investigated whether acute phase proteins (APPs) could serve as EPM markers. They presented the results of their work at the Second EPM Workshop, held Oct. 25-27, 2017, in Tahoe City, California.

“One of the big problems with EPM diagnosis is the discrepancy between the high seroprevalence and the very low incidence of clinical disease,” said Johnson. In fact, most horses with evidence of exposure never get sick. Then, for the horses that do, the gold standard for diagnostic confirmation is a combination of true neurologic signs of disease, exclusion of other potential causative diseases, and evidence of intrathecal antibody production—that is, antibodies against S. neurona produced within the nervous system.

“Acute-phase proteins are produced by the liver and are known to rise very rapidly in response to infection and inflammation,” she said, and could potentially be used in concert with blood tests—which alone produce a lot of false positives. The New Bolton research team, led by Neil Mittelman, DVM, an internal medicine resident, looked at the two most commonly studied APPs: C-reactive protein (CRP) and serum amyloid A (SAA)

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:

Which is your favorite Olympic equestrian event?
111 votes · 111 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!