Veterinary Record 173:249 doi:10.1136/vr.101714
  • Research
  • Short communication

Evaluation of the kinetics of antibodies against Sarcocystis neurona in serum from seropositive healthy horses without neurological deficits treated with ponazuril paste

  1. P. A. Conrad, DVM2
  1. 1Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
  2. 2Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
  3. 3W. R. Pritchard, Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
  4. 4Skyline Equine, San Mateo, CA 94403, USA
  1. E-mail for correspondence: npusterla{at}

Equine protozoal myeloencephalitis (EPM) is a debilitating protozoal disease of the CNS that is typically caused by infection with Sarcocystis neurona and less frequently with Neospora hughesi (Sellon and Dubey 2007). Although the epidemiology of S neurona has been well characterised, the diagnostic modalities, long-term implications and response to treatment are not fully understood. The diagnosis of EPM is often based on the presence of antibodies against S neurona in serum and/or cerebrospinal fluid (CSF; Furr and others 2002). The introduction of a quantitative indirect fluorescent antibody test (IFAT) for the detection of specific antibodies against S neurona has enabled equine veterinarians to better determine the likelihood of infection in a horse with neurological deficits (Duarte and others 2004). Many equine veterinarians routinely use the IgG IFAT for S neurona to aid in the diagnosis of EPM and also to help guide treatment duration and determine when successful treatment has been achieved. However, practicing veterinarians have reported that specific antiprotozoal treatment appears not to influence reduction of antibody levels against S neurona. The goal of this study was to determine the temporal trends in antibody levels against S neurona in seropositive horses following administration of ponazuril paste.

The study was performed at one large farm located in northern California. The farm had previously had confirmed cases of EPM, but there were no current cases. Prior to study commencement, 61 adult healthy, warmblood horses with no …

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