Inference of molecular phylogeny of Sarcocystis felis [sarcocystidae] from cats based on nuclear-encoded ribosomal gene sequences

ABSTRACT

The phylogenetic position of four clinical isolates of Sarcocystis felis was assessed using ssurRNA and ITS 1 gene sequences in the context of a wide array of other Sarcocystis sp. Phylogenetic reconstructions using neighbour-joining and maximum parsimony methods generated identical tree topologies with strong support values at each node. High ssurRNA sequence similarity [>/= 99%] and the resulting phylogeny demonstrated that S. felis and S. neurona are significantly closely related to each other. The two Sarcocystis formed a monophyletic group distinct from the other Sarcocystis sp., irrespective of the alignment algorithms or tree-building method used. The absolute [100%] identity of ssurRNA sequences of sarcocysts and sporocysts obtained from one cat raised the question regarding the cat's role as a potential intermediate host besides its known role as a definitive host of S. felis. On the other hand, S. felis sarcocyst DNA sequence was found to be quite dissimilar over the ITS 1 region when compared to S. neurona. These findings indicated that using sequences from 'two different genetic loci provided a stronger comparative basis than would have been possible using either one