Submitted to: Journal of Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2002
Publication Date: 9/1/2002
Citation: Stanek, J.F., Dubey, J.P., Oglesbee, M.J., Reed, S.M., Lindsay, D.S., Capitini, L.A., Njoku, C.J., Vittitow, K.L., Saville, W.J. 2002. Life cycle of sarcocystis neurona in its natural intermediate host, raccoon (procyon lotor). Journal of Parasitology 88:1151-1158. Interpretive Summary: Sarcocystis neurona is a single-celled parasite of animals. It causes a fatal nemologic disease of horses called equine protozoal myeloencephalitis (EPM). EPM-like disease has also been reported in cats, mink, sea otters, seals, skunks and raccoons. The life cycle of this parasite is not fully known. Scientists at the Beltsville Agricultural Research Center and the Ohio State University report for the first time its complete life cycle in the laboratory-raised raccoons. These findings would be of interest to biologists, parasitologists and veterinarians.
Technical Abstract: Sarcocystis neurona causes encephalomyelitis in many species of mammals and is the most important cause of neurologic disorders in the horse. Its complete life cycle is unknown, particularly its development and localization in the intermediate host. Recently, raccoon was recognized as a natural intermediate host of S. neurona. In the present study, migration and development of S. neurona was studied in 10 raccoons (Procyon lotor) fed S. neurona sporocysts from experimentally-infected opossums; 4 raccoons served as controls. Raccoons were examined at necropsy 1, 3, 5, 7, 10, 14, 15, 22, 37 and 77 days after feeding sporocysts (DAFS). Tissue sections of most organs were studied histologically and reacted with anti-S. neurona-specific polyclonal rabbit serum in an immunohistochemical test. Parasitemia was demonstrated in peripheral blood of raccoons 3 and 5 DAFS. Individual zoites were seen in histologic sections of intestines of raccoons euthanized 1, 3, and 5 DAFS. Schizonts and merozoites were seen in many tissues 7 to 22 DAFS, particularly in the brain. Sarcocysts were seen in raccoons killed 22 DAFS. Sarcocysts at 22 DAFS were immature and seen only in skeletal muscle. Mature sarcocysts were seen in all skeletal samples, particularly in the tongue of the raccoon at 77 DAFS; these sarcocysts were infective to laboratory-raised opossums. This is the first report of complete development of S. neurona schizonts and sarcocysts in a natural intermediate host.