AAEP Veterinarians Discuss Diagnostic Options for EPM

During the "Diagnostic Options for EPM" (equine protozoal myeloencephalitis) table topic session at the 2013 American Association of Equine Practitioners (AAEP) convention, held Dec. 7-11 in Nashville, Tenn., 35 veterinarians discussed several areas of EPM, including:

  • The different commercially available diagnostic platforms (Western blot, SAG-ELISAs, IFAT);
  • The biology of apicomplexan protozoal parasites (e.g., EPM’s causative organisms Sarcocystis neurona and Neospora hughesi);
  • The pros and cons of testing blood serum alone versus serum and cerebrospinal fluid (CSF) together;
  • The use of repeated antibody testing to determine response to antiprotozoal treatment; 
  • The applications and pharmacokinetics of commercially available antiprotozoal drugs (e.g., Marquis, Protazil, ReBalance);
  • The use of immunomodulators for EPM treatment;
  • The use of antiprotozoal drugs for preventing EPM in high-risk horses; and
  • The use of advanced imaging modalities (such as MRI and computed tomography) to diagnose EPM.

The practitioners shared evidence-based information regarding the protozoal pathogens’ biology, the validation of serological tests, and pharmacokinetic (the factors affecting the disposition of the drug in the body, which in turn affects the onset, duration, and magnitude of effect) data. They also presented preliminary data on loading doses of antiprotozoal drugs and pharmacokinetic studies of subtherapeutic doses of antiprotozoal drugs for preventing EPM (data previously presented at either an AAEP convention or the American College of Veterinary Internal Medicine Forum).

The attendants were very engaged and shared personal experiences in the different fields. The group seemed to agree that available diagnostic platforms offer similar accuracy and that available antiprotozoal drugs appear to be equally safe and effective. They discouraged repeated testing of peripheral blood antibody titers to S. neurona or N. hughesi following completion of antiprotozoal treatment due to the lack of data and the subjective impression that titers did not necessarily correlate with clinical improvement. Instead, the veterinarians recommended using clinical improvement to make decisions regarding length of treatment.

The group raised several yet unanswerable questions mainly in regard to antibody kinetics to S. neurona and N. hughesi and to the benefit of using antiprotozoal drugs to prevent EPM. Due to the empirical nature of several protocols and the lack of evidence-based information in various fields discussed, the group recognized the need to support future research in the epidemiological, preventive, and diagnostic fields.

This session was moderated by Stephen Reed, DVM, Dipl. ACVIM, an internal medicine specialist at Rood & Riddle Equine Hospital, in Lexington, Ky., and Nicola Pusterla, DVM, PhD, Dipl. ACVIM, a professor of equine internal medicine at the University of California, Davis, School of Veterinary Medicine.

About the Author

Nicola Pusterla, DVM, PhD, Dipl. ACVIM

Nicola Pusterla, DVM, PhD, Dipl. ACVIM, is currently an associate professor of equine internal medicine at the University of California, Davis, School of Veterinary Medicine, as well as chief of large animal medicine and section head of equine medicine and dentistry. Pusterla’s research focuses on selected aspects of equine infectious diseases with an emphasis on epidemiology, clinical disease understanding, diagnostics, prevention, and treatment.

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