Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2001
Publication Date: N/A
Interpretive Summary: Sarcosystis neurona is a single-celled parasite of animals. It causes a fatal illness, called equine protozoal myeloencephalitis (EPM), in horses. It is one of the most serious diseases of horses in the United States. There is no suitable large animal model to study EPM. Scientists at the Beltsville Agricultural Research Center and the U.S. Army Institute in Frederick, Maryland, describe pathogenesis and lesions of EPM in an immunodeficient mouse. These results would be useful to parasitologists, biologists, and pathologists.
Pathologic changes were studied in 27 interferon-gamma knockout mice 34 to 54 days after being fed graded doses of Sarcocystis neurona sporocysts derived from a naturally-infected opossum. By light microscopy, the target tissue for S. neurona infection was the CNS. Characteristic histopathologic changes present in all mice consisted of an inflammatory infiltrate consisting of mostly polymorphonuclear leukocytes and macrophages, fewer eosinophils and rare multinucleated giant cells. There were intralesional protozoa and scattered subacute perivascular cuffs. Where the infiltrates were extensive, there was frequently malacia. Pathologic changes were much more frequent and severe in the caudal portion of the brain, especially in the cerebellum, than in the middle and cranial portions. Changes were present in all spinal cords examined (10/10). Lesions were equally distributed in white and gray matter of the brain and spinal cord and their meningeal linings. The use of rabbit anti-S. neurona serum helped us to detect the organisms.