Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 1999
Publication Date: N/A
Interpretive Summary: Parasites of the genera Sarcocystis and Frenkelia are related single-celled parasites of humans and animals. Certain species of Sarcocystis can cause anemia, abortion, and death in livestock. The separation of the genera Frenkelia and Sarcocystis is controversial. Scientists at the Beltsville Agricultural Research Center and University of Technology in Sydney, Australia compared full-length large subunit ribosomal RNA gene sequences from several species of Sarcocystis and Frenkelia and concluded that they were very closely related and proposed synonymising the genus Frenkelia with Sarcocystis. These results will be of interest to parasitologists.
The different genera currently classified into the family Sarcocystidae include parasites which are of significant medical, veterinary, and economic importance. The genus Sarcocystis is the largest within the family Sarcocystidae and consists of species which infect a broad range of animals including mammals, birds, and reptiles. Frenkelia, another genus within this family, consists of parasites that use rodents as intermediate hosts and birds of prey as definitive hosts. Both genera follow an almost identical pattern of life cycle, and their life cycle stages are very similar morphologically. However, the relationship between the two genera remains unresolved because previous analyses of phenotypic characters and of small subunit ribosomal RNA gene sequences have questioned the validity of the genus Frenkelia or the monophyly of the genus Sarcocystis if Frenkelia was recognised as a valid genus. We therefore subjected the large esubunit ribosomal RNA gene sequences of representative taxa in these gener to phylogenetic analyses to ascertain a definitive relationship between the two genera. The full length large subunit ribosomal RNA gene sequences obtained were aligned using Clustal and DCSE secondary structure alignments. The DCSE alignment was then split into two data sets, one including helical regions, and one including non-helical regions, in order to determine the more informative sites. Subsequently, all four alignment data sets were subjected to different tree-building algorithms. All of the analyses produced trees supporting the paraphyly of the genus Sarcocystis if Frenkelia was recognised as a valid genus and, thus, call for a revision of the current definition of these genera. However, an alternative, more parsimonious and more appropriate solution to the