Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 10, 2000
Publication Date: N/A
Interpretive Summary: Sarcocystis neurona is a single celled parasite of companion animals and wild animals. It causes a fatal disease in horses called equine protozoal myeloencephalitis (EPM). The full life cycle of S. neurona is not known. In horses the parasite is confined to the brain and spinal cord. A scientist at the Beltsville Agricultural Research Center reports the route of migration and developmental stages of S. neurona in mice fed sporocysts (resistant stage) from opossum intestines. These results should help in tracing the parasite in tissues of infected horses. The results would be of interest to pathologists, parasitologists and equine practioners.
Migration and development of Sarcocystis neurona was studied in 46 gamma interferon knockout mice fed graded doses of S. neurona sporocysts from the intestine of a naturally infected opossum. Mice were examined at necropsy 1 to 32 days after feeding sporocysts (DAFS). All tissue sections were reacted with anti-S. neurona-specific polyclonal rabbit serum in an immunohistochemical (IHC) test. Between 1 and 3 DAFS, organisms were seen mainly in intestines. Between 4 and 11 DAFS, organisms were seen in several visceral tissues. Beginning with 13 DAFS, schizonts and merozoites were present in sections of brains of all infected mice. All regions of the brain were parasitized but the hind brain was most severely affected. Sarcocystis neurona was found in the spinal cord of all 10 mice examined 22-30 DAFS. Organisms were seen rarely in sections of heart and eye and were occasionally present in lungs. More organisms were seen in IHC- stained sections than in sections stained with hematoxylin and eosin. Treatment of tissues with glutaraldehyde, Karnovsky fixative, and EDTA did not affect staining of organisms by IHC.