Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 5, 2000
Publication Date: N/A
Interpretive Summary: The genetic diversity and geographic range of Sarcosystis parasites transmitted by opossums is assessed through comparison of sequenced genes from disparate geographic isolates and from an array of American opossum species. Distinct species of opossums in North and South America are demonstrated for the first time to be transmitting genetically similar forms of S. neurona and s. falcatula, as well as other unnamed strains which may constitute other parasite species.
At least 3 species of Sarcocystis (S. neurona, S. falcatula, S. speeri) have recently been shown to use opossums of the genus Didelphis as their definitive host. In order to evaluate the evolutionary relationships among Sarcocystis sp. isolates from the Americas, and to determine whether organisms representing the same parasite lineages are transmitted north and south of the Panamanian isthmus, we inferred the phylogenetic relationships from nucleotide sequence variation in parasites isolated from 3 opossum species (D. virginiana, D. albiventris, D. marsupialis). In particular, we used variation in the 25/396 marker to compare several isolates from Brazil, Argentina, and the United States to each other and to cloned S. neurona and S. falcatula whose morphologies and host affinities have been defined in the laboratory. Sarcocystis neurona was identified from a Brazilian D. albiventris, as well as from North American D. virginiana. Parasites resembling the Cornell strain of S. falcatula are transmitted both south and north of the Panamanian isthmus by D. albiventris and D. virginiana, respectively. Distinct attributes at 2 genetic loci differentiated a Brazilian isolate of S. falcatula from all other known parasite lineages. We confirm S. neurona as the causative agent of recently reported neurologic disease in Southern sea otters. The widespread distribution of certain species of Sarcocystis may derive from their ability to parasitize migratory bird hosts in their intermediate stage.