EQUINE PROTOZOAL MYELOENCEPHALITIS IN A THREE-YEAR-OLD MANGALARGA MACHADOR FOAL: CASE REPORT

Abstract

Equine Protozoal Myeloencephalitis (EPM) is a neurological disease of high clinical and sanitary relevance, caused by the protozoan Sarcocystis neurona and, less frequently, by Neospora hughesi. It is recognized as one of the leading causes of neurological dysfunction in horses in the Americas. The epidemiological cycle involves opossums (Didelphis spp.) as definitive hosts, which shed sporocysts into the environment and contaminate water and feed consumed by horses, which act as aberrant intermediate hosts. Clinical signs vary depending on where lesions occur in the central nervous system. Common signs include asymmetric ataxia, weakness, incoordination, cranial nerve paresis, facial flaccidity, and dysphagia, with either gradual progression or, in some cases, acute onset. Diagnosis remains challenging and is based on a thorough neurological examination, exclusion of differential diagnoses, and detection of specific antibodies in serum and cerebrospinal fluid using tests such as ELISA and indirect immunofluorescence. Treatment involves antiprotozoal drugs such as diclazuril, ponazuril, or the sulfadiazine–pyrimethamine combination, often combined with anti-inflammatory drugs, dimethyl sulfoxide, and antioxidant supplementation. This study reported a case of EPM in a Mangalarga Marchador filly, diagnosed based on compatible neurological signs and serological confirmation of S. neurona. Early therapy with diclazuril, antioxidants, and dimethyl sulfoxide led to complete clinical recovery, with no residual neurological deficits. This case highlights the importance of early diagnosis, appropriate therapeutic management, and preventive measures, including controlling opossums and protecting feed and water sources.