A recent study by researchers at the University of California, Davis School of Veterinary Medicine revealed that equine protozoal myeloencephalitis (EPM), caused by two different parasites, is widespread throughout the United States. The single-celled protozoal parasite Sarcocystis neurona which is shed in the feces of opossums is the most commonly recognized cause of this neurological disease in horses. However, this study found evidence that Neospora hughesi, the other EPM-causing parasite, first identified in California, is now being identified in horses across the United States. After obtaining a total of 3,123 diagnostic submissions from 49 states, UC Davis determined that horses from 42 states were affected by parasites causing EPM. Horses in 24 states tested positive for antibodies against Neospora hughesi and Sarcocystis neurona. Horses from 17 states tested positive for antibodies against Sarcocystis neurona only, while horses in one state tested positive for antibodies against Neospora hughesi only. As these results show a widespread distribution of the parasites causing EPM, horse owners and practitioners should test EPM-suspect horses for antibodies against both parasites.
"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 SarcoFluorTM and NeoFluorTM tests created by UC Davis are immunofluorescent antibody tests for both of the known causative agents of EPM (Sarcocystis neurona and Neospora hughesi). These tests provide a quantitative indication of EPM infection and provide greater sensitivity and specificity than the Western immunoblot test on serum samples. UC Davis' tests also reduce the necessity to obtain cerebrospinal fluid in order to screen for antibodies against the two protozoal agents.
"UC Davis has a rich history and culture of combining rigorous peer-reviewed research with cutting edge medicine," said Dr. Patricia Conrad, professor and head of the laboratory at UC Davis that developed the tests. "The resources and EPM team of clinicians and scientists available at UC Davis have allowed us to validate these more effective tests. We are committed to improving the reliability of EPM testing, and are pleased to offer this service to our clients at a reasonable cost."
More than a decade ago, researchers at UC Davis were determined to create better testing for EPM. To that end, the School of Veterinary Medicine started an investigative effort to develop a better diagnostic tool, and has been offering the tests to clients with tremendous success for several years.
"Since its discovery in horses, EPM has posed a significant diagnostic and therapeutic challenge," said Dr. Claudia Sonder, director of the Center for Equine Health at UC Davis. "These new diagnostic tools are a product of the team science that changes clinical outcomes for horses treated at UC Davis. For the first time, veterinarians can associate probability of EPM infection with positive tests results, and can rule out both organisms known to cause EPM with negative tests. This advancement in diagnostic capability is much welcomed by all faced with this complicated disease."
The SarcoFluorTM and NeoFluorTM tests are available through the laboratory services at the UC Davis Veterinary Medical Teaching Hospital.
Image Courtesy of: UC Davis Veterinary Medical Teaching Hospital
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