THE PHYLOGENY OF NEOSPORA-CANINUM

Morphological studies by electron microscopy on the protozoan Neospora caninum have shown that this organism possesses a subcellular structu re typical of parasites classified in the family Sarcocystidae, subcla ss Coccidiasina of the phylum Apicomplexa. Using a strategy based on D NA sequence analysis of products derived by asymmetric PCR to determin e the nucleotide sequences, we have tested the validity of this classi fication by comparing the small subunit ribosomal RNA (18S rRNA) gene sequences of N. caninum with those of other parasitic protozoa classif ied in the phylum Apicomplexa. The results of this analysis confirm th e placing of N. caninum in the family Sarcocystidae and place it as a sister group to Toxoplasma gondii in the phylum Apicomplexa.