Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 1999
Publication Date: N/A
Interpretive Summary: Sarcocystis neurona is a protozoan (single-celled) parasite. It causes equine protozoal myeloencephalitis (EPM) in horses. EPM is the most common cause of neurological disorders in horses. Affected horses may develop lameness, paralysis, and some die acutely. Sarcocystis neurona is found in the brain and spinal cord of horses. The opossum (Didelphis virginiana) is considered the reservoir host for S. neurona and the resistant stage of the parasite (oocyst) is shed in opossum feces. Until recently, Sarcocystis neurona was misdiagnosed as Sarcocystis falcatula for which opossums are also the reservoir hosts. Scientists at the Beltsville Agricultural Research Center and Virginia Tech, Blacksburg, have differentiated S. neurona and S. falcatula in cell culture. The growth characteristics will help parasitologists to study the biology of these closely related parasites.
The development of Sarcocystis falcatula merozoites in bovine turbinate cell (BT) cultures is described and compared with development of Sarcocystis neurona merozoites. Merozoites of S. falcatula entered BT cell cultures and increased in size until 3 days postinoculation when the nucleus of some merozoites developed lobes. Developing schizonts present at 4 days contained a lobed nucleus or appeared multinucleate. A single mature schizont was observed 4 days p.i. Schizonts were numerous 5 and 6 days p.i. Merozoites were produced from blastophores on the schizont. Sarcocystis neurona merozoites developed to mature schizonts by 3 days p.i. in BT cells and a residual body was often present. Transmission electron microscopy revealed that S. falcatula merozoites possessed more micronemes than did S. neurona merozoites. Our study demonstrates that S. falcatula and S. neurona are not the same parasite.