Sarcocystis neurona,Neosporaspp. andToxoplasma gondiiinfections in horses and equine protozoal myeloencephalitis (EPM): five decades of personal experience, perspectives and update

Abstract Sarcocystis neurona,Neosporaspp. andToxoplasma gondiiare related protozoans; they were considered the same parasite until 1970s. Two of these parasites,S. neuronaandNeosporaspp. are associated with a neurological syndrome in horses, called equine protozoal myeloencephalitis (EPM). The diagnosis and treatment of EPM are difficult. Most cases of EPM are related toS. neuronawhile only a few are due toNeosporaspp. infections. There are two species ofNeospora,Neospora caninumthat has a wide host range andNeospora hughesithat has been found only in horses. Currently,T. gondiiis not considered as a cause of EPM in horses, although it causes neurological illness in many other hosts, including humans. The present review provides an update on history, life cycle, diagnosis and treatment of these three infections in horses.