Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 10, 2000
Publication Date: N/A
Interpretive Summary: Equine protozoal myeloencephalitis (EPM) is the most common cause of neurologic disorders in horses in North America. The disease is caused by a parasite (Sarcocystis neurona) which has only been found in brain or spinal cord of affected animals. A similar disease is seen in raccoons and has been documented from several locations in the United States. Although this sparasitic infection has been reported in skunk, mink, cat, sea otters, Pacific harbor seals, and a pony, its life cycle of has not been fully documented. In all the reported cases, the parasites have been found only in the tissues of the nervous system. Since raccoons share our immediate environment, they are considered good monitors of zoonotic diseases and environmental contamination due to pollutants. In a survey of 84 raccoons we found 3 raccoons with the parasitic infection (3.6 % prevalence) at Corvallis, Oregon, USA. Two of the affected animals also had inflammation in the heart and 1 revealed the parasite within the affected heart muscle. Since 2 positive raccoons were found next to horse facilities (a veterinary clinic and a horse riding establishment) it may suggest that horses in this geographical location of Oregon may also be at risk of acquiring EPM. Prior to this report, the parasites had been seen only in tissues of the central nervous system. Therefore, the presence of concurrent inflammation of the heart and the presence of the parasites in the present study is of interest. These findings may either have been overlooked in the past or the organism (S. neurona) may now have become more virulent and capable of infecting non-neural tissues. If the latter is valid, then diagnostic pathologists should be aware of the possibility of finding similar myocardial involvement with S. neurona in other susceptible animals.
Technical Abstract: Sarcocystis neurona associated granulomatous encephalitis was found in 2 of 84 adult raccoons. Both raccoons also had extensive nonsuppurative myocarditis and 1 had S. neurona schizonts and merozoites in the myocardium. Only the asexual stages (schizonts and merozoites) of S. neurona are found in tissues of naturally infected animals (horse, mink, raccoons, cats, skunk, pony, seals, sea otter) and since these have not been reported outside of the central nervous system, the presence of concurrent myocarditis in raccoons with the presence of S. neurona in the current study is of interest. Pathologists should consider the possible association of S. neurona with myocardial inflammation in other S. neurona susceptible animals.