Submitted to: Journal of Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/1999
Publication Date: N/A
Citation: Interpretive Summary: Equine protozoal myeloencephalitis (EPM) is a neurologic protozoan (single- celled) parasite disease of horses. A parasite most often associated with EPM is Sarcocystis neurona. Horses become infected when they ingest feed and water contaminated with sporocysts (resistant stage) of the parasite excreted in feces of the opossum (Didelphis virginiana). The antemortem diagnostic test for EPM is based on the detection of antibodies to S. neurona in cerebrospinal fluid of the affected horse using antigen derived from in vitro cultured merozoites. Scientists at the Beltsville Agricultural Research Center and the Montana State University and Oregon State University have standardized conditions for optimal growth of S. neurona. These studies will be useful to biologists, diagnosticians and parasitologists.
Technical Abstract: The development and merozoite production of Sarcocystis falcatula and 2 isolates (SN6 and SN2) of S. neurona were studied in various cultured cell lines. All 3 parasites underwent multiple cycles of schizogony in VERO cells, bovine monocytes (M617 cells), and bovine pulmonary artery endothelial cells (CPA). Sarcocystis neurona strains SN6 and SN2 formed schizonts in rat myoblasts (L6) but not in quail myoblasts (QM7); S. falcatula formed schizonts in QM7 cells but not in L6 cells. Merozoites did not develop to sarcocysts in the myoblast cell lines. During a 47 day culture period in VERO cells, SN6 produced substantially more merozoites than did SN2 of S. falcatula. M617 cells were found to produce substantially more merozoites of SN6 than did VERO or CPA cells. During a 17 day culture period of SN6, M617 cells produced mean totals of 4.7 x 108 merozoites; VERO cells produced 1.9 x 108 merozoites; and CPA cells produced 5.9 x 107 merozoites. At 4-12 days after inoculation of cultured cells with SN6, M617 cells cultured in the presence of 10% FBS produced a mean merozoite total of 5.1 x 108 compared to 3.6 x 108 for culture medium containing 1% FBS.