|Fenger Clara K|
Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/1994
Publication Date: N/A
Citation: Interpretive Summary: Equine protozoal myeloencephalitis (EPM) is a fatal disease of horses confined to the Americas. Its life cycle and source of infection are unknown. The etiologic agent of EPM, Sarcocystis neurona was recently grown in cell cultures inoculated with homogenates of tissues from affected horses. A carnivore host is thought to be the main source of infection but tit has not been yet identified. At present there are no clues to the life cycle of S. neurona. Scientists at the Beltsville Agricultural Research Center and the University of Kentucky have compared ribosomal subunit gene structure of S. neurona with other species of Sarcocystis whose life cycles are known. Thus results confirm that S. neurona is indeed related to other species of Sarcocystis. This information will be useful in studying the life cycle of Sarcocystis neurona.
Technical Abstract: Sarcocystis neurona is a coccidial parasite which causes a neurologic disease of horses in North and South America. The natural host species are not known, and classification is based on ultrastructural analysis. The small ribosomal subunit (SSURNA) gene of S. neurona was amplified using polymerase chain reaction techniques, and sequenced by Sanger sequences reactions. The sequence was compared with sequences of S. muris, S. gigantea, S. tenella, S. cruzi, S. arieticanis, Toxoplasma gondii, Eimeria tenella and Cryptosporidium parvum. Alignments of available sites for all eight species, the same sites with invariant positions excluded and alignments of entire SSURNA sequence of S. neurona, S. muris, S. cruzi, T. gondii and C. parvum were performed. Alignments were analyzed using maximum parsimony and distance matrix methods to determine relative phylogeny of their organisms. These analyses confirmed placement of S. neurona in the genus Sarcocystis, and suggested a close relationship to S. muris, S. gigantea and T. gondii. Molecular phylogeny suggests that Sarcocystis spp. which utilize the dog (Canis familiaris) as the definitive host evolved from a common ancestor, whereas those species (including T. gondii) which utilize the cat (Felis domesticus) as the definitive host evolved from another common ancestor. This suggests a possible definitive host for S. neurona.