Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 19, 2006
Publication Date: May 19, 2006
Citation: Lindsay, D.S., Mitchell, S.M., Yang, J., Dubey, J.P., Gogal, Jr, R.M., Witonsky, S.G. 2006. Penetration of equine leukocytes by merozoites of sarcocystis neurona. Veterinary Parasitology. 138:371-376.
Interpretive Summary: Sarcocystis neurona is a single-celled parasite. It causes a fatal disease in horses called Equine Protozoal Myeloencephalitis (EPM). EPM also occurs in other animals. Opossums are the definitive host for this parasite, and the main reservoir of infection. Opossums become infected by consuming the encysted stage of the parasite (sarcocyst) in infected animal tissue and they excrete millions of the resistant stage (oocysts) in their feces. Horses become infected by ingesting food and water contaminated with oocysts.
Scientists at the Beltsville Agricultural Research Center and Virginia Tech, Backsburg report host parasite relationship of S. neurona in cell culture.The results will be of interest to biologists, parasitologists, and veterinarians.
Horses are considered accidental hosts for Sarcocystis neurona and they often develop severe neurological disease when infected with this parasite. Schizont stages develop in the central nervous system (CNS) and cause the neurological lesions associated with equine protozoal myeloencephalitis. The present study was done to examine the ability of S. neurona merozoites to penetrate and develop in equine peripheral blood leukocytes. These infected host cells might serve as a possible transport mechanism into the CNS. S. neurona merozoites penetrated equine leukocytes within 5 minutes of co-culture (PC). Infected leukocytes were usually monocytes. Infected leukocytes were present up to the final day of examination at 3 days PC. Up to three merozoites were present in an infected monocyte. No development to schizont stages was observed. All stages observed were in the host cell cytoplasm. We postulate that S. neurona merozoites may cross the blood brain barrier hidden inside leukocytes. Once inside the CNS these merozoites can egress and invade additional cells and cause encephalitis.