Submitted to: International Meeting on Molecular Epidemiology and Evolutionary Genetics in Infectious Disease
Publication Type: Abstract Only
Publication Acceptance Date: June 30, 2004
Publication Date: July 19, 2004
Citation: Asmundsson, I.M., Dubey, J.P., Rosenthal, B.M. 2004. Characterization of microsatellite markers in Sarcocystis neurona. Abstract. International Meeting on Molecular Epidemiology and Evolutionary Genetics in Infectious Disease. Paper No. 383.
Interpretive Summary: New genetic tools have been developed to determine the extent and pattern of genetic variation within and among closely related parasites, excreted by opossums, belonging to the genus Sarcocystis. Analysis of such variation, when completed, should help determine the whether those parasites responsible for Equine Protozoal Myeloencephalitis comprise a single strain, an assemblage of strains, or a population of freely interbreeding individuals. The analysis will also uncover how these pathogenic parasites relate to similar organisms that do not induce neurological disease.
Genetic analyses of Toxoplasma gondii have revealed an unusual population structure comprising three distinct, but highly similar genotypes. These few, clonally reproducing strains persist despite well documented sexual reproduction in cats. The ability of these tissue-cyst forming coccidian parasites to disseminate asexually, circumventing the definitive host, surely has contributed to their geographically widespread dispersal across many host species. We are interested in determining whether such a population structure is unique or is instead typical, of closely related genera. We have therefore characterized microsatellite markers from Sarcocystis neurona, a causative agent of Equine Protozoal Myeloencephalitis, and one of several parasite taxa excreted by New World opossums. Microsatellites were isolated from a library of genomic restriction fragments enriched for repeat regions using biotinylated oligonucleotide probes containing microsatellite repeats and streptavidin beads. These markers will be used to explore whether the genetic structure of Sarcocystis neuron is partitioned among distinct non-recombinant clonal lineages, and will also clarify the evolutionary relationship among Sarcocystis spp. isolates using the opossum as their definitive hosts including, but not limited to, those of three Sarcocystis spp. (S. neurona, S. falcatula, and S. speeri) found in the New World marsupial, Didelpis virginiana. Preliminary application of these markers indicates that a sample presumed to represent S. neurona include groups of individuals consistently demarcated by distinct alleles at multiple, independent loci.