A study by University of California-Davis School of Veterinary Medicine researchers finds the neurological disease equine protozoal myeloencephalitis (EPM) is widespread across the United States.
A single-cell protozoal parasite, Sarcocystis neurona, shed in the feces of opossums is the most commonly recognized cause of EPM. However, evidence shows that Neospora hughesi, the other EPM-causing parasite is now being identified in horses across the United States. It was first identified in California.
Researchers obtained a total of 3,123 diagnostic submissions from 49 states for the study. They determined that horses from 42 states were affected by parasites causing EPM.
Horses in 24 states tested positive for antibodies against N. hughesi and S. neurona. Horses from 17 states tested positive for antibodies against S. neurona only, while horses in one state tested positive for antibodies against N. hughesi only.
“This study returned positive results from more states than we originally thought,” said UC Davis’ Dr. Nicola Pusterla, lead researcher on the study.” As the recognized geographic spread of Neospora hughesi infections expands, we are encouraging horse owners about the benefits of the advanced tests available at UC Davis to more accurately diagnose the disease. Overall, we had not been satisfied with the standard testing available, so we have spent the past decade developing and successfully validating an improved diagnostic tool for EPM.”
The immunofluorescent antibody tests SarcoFluor and NeoFluor created by UC-Davis are designed to identify both of the known causative agents of EPM. The university says the tests provide a quantitative indication of EPM infection and provide greater sensitivity and specificity than the Western immunoblot test on serum samples while reducing the necessity to obtain cerebrospinal fluid in order to screen for antibodies against the two protozoal agents.
“Since its discovery in horses, EPM has posed a significant diagnostic and therapeutic challenge,” says Claudia Sonder, DVM, director of the Center for Equine Health at UC-Davis. “For the first time, veterinarians can associate the probability of EPM infection with positive tests results and can rule out both organisms known to cause EPM with negative tests.”
EPM is known as a master of disguise because it can be so difficult to diagnose and symptoms can range from mild to severe, according to AAEP. Clinical signs are often asymmetrical and may include incoordination, abnormal gait, muscle atrophy, paralysis of muscles of the eyes, face or mouth, and difficulty swallowing. Some horses may experience seizures and a head tilt.
Horse owners can minimize their horses’ risk by practicing good habits on the farm including keeping feed rooms and containers closed and sealed.