Phylogenetic Analysis of Coccidia Based on 18S rDNA Sequence Comparison Indicates that Isospora Is Most Closely Related to Toxoplasma and Neospora

Abstract

The phylogenetic relationships and taxonomic affinities of coccidia with isosporan-type oocysts have been unclear as overlapping characters, recently discovered life cycle features, and even recently discovered taxa, continue to be incorporated into biological classifications of the group. We determined the full or partial 18S ribosomal RNA gene sequences of three mammalian Isospora spp., Isospora felis, Isospora ohioensis and Isospora suis, and a Sarcocystis sp. of a rattlesnake, and used these sequences for a phylogenetic analysis of the genus Isospora and the cyst-forming coccidia. Various alveolate 18S rDNA sequences were aligned and analyzed using maximum parsimony to obtain a phylogenetic hypothesis for the group. The three Isospora spp. were found to be most closely related to Toxoplasma gondii and Neospora caninum. This clade in turn formed the sister group to the Sarcocystis spp. included in the analysis. The results confirm that the genus Isospora does not belong to the family Eimeriidae, but should be classified together with the cyst-forming coccidia in the family Sarcocystidae. Furthermore, there appear to be two lineages within the Sarcocystidae. One lineage comprises Isospora and the Toxoplasma/Neospora clade which share the characters of having a proliferative phase of development preceding gamogony in the definitive host and an exogenous phase of sporogony. The other lineage comprises the Sarcocystis spp. which have no proliferative phase in the definitive host and an endogenous phase of sporogony.

Application of polymerase chain reaction (PCR) in parasitology

“…suis συν δέονται περισσότερο με το Toxoplasma gondii και Neospora caninum 17 . Τα αποτελέσματα αυτά δείχνουν ότι το γένος Isospora πρέπει να καταταχθεί στην οικογένεια Sarcocystidae αντί για την Eimeriidae που κατατασσόταν μέχρι τιόρα 17 .…”

A new Caryospora coccidian species (Apicomplexa: Eimeriidae) from the laughing kookaburra (Dacelo novaeguineae)

“…Isospora Barta (1997), Barta et al (2001), Carreno et al (1998Carreno et al ( , 1999, 353 Dalrymple et al (1992), Holmdahl et al (1999), Jeffries et al 354 (1997), Morgan et al (1999), Seville et al (2006), Tenter and 355 Johnson (1997). Q9 356…”

Foundations for an Integrative Parasitology: Collections, Archives, and Biodiversity Informatics

“…A growing number of applied research programs in parasitology have recognized this and are using phylogenetic information in their studies. Although the taxonomic impediment remains apparent, there has been attention to development of phylogenies for groups that include important helminth parasites of humans and livestock (e.g., for ascaridoid nematodes, Nadler and Hudspeth, 2000; trichostrongyloid nematodes, Hoberg and Lichtenfels, 1994;Gouÿ de Bellocq et al, 2001; taeniid tapeworms, Hoberg, Alkire, et al, 2001), and phylogenetic approaches have figured prominently in recent studies of the Apicomplexa (e.g., Barta, 1989;Carreno et al, 1998).…”