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Results of molecular determination of a dog isolate of Neospora caninum in the Czech Republic are presented. Colorless bisporocystic oocysts measuring 10-13 micro m x 10-11 micro m were recovered from feces and used for DNA isolation. A diagnostic PCR procedure using previously described molecular methods was performed to determine the species. The N. caninum species-specific primers based on the Nc 5 region produced a positive result, while primers specific for Hammondia heydorni rDNA internal transcribed spacer 1 (ITS1) was negative. Sequencing and phylogenetic comparison of ITS1 rDNA and the D2 domain of the large subunit rDNA (D2 LSU) determined our isolate to be N. caninum. Phylogenetic analysis of closely related genera Toxoplasma, Neospora and Hammondia based on ITS1 and D2 LSU robustly distinguished three clades: (i). Toxoplasma gondii + Hammondia hammondi, (ii). N. caninum + Neospora hughesi, and (iii). H. heydorni. Based on phylogenetic relationships we propose three acceptable suggestions to solve the problem of taxonomy of these genera.

Adult severe combined immunodeficient (SCID) mice were inoculated with oocysts of 13 different Caryospora (Protozoa, Apicomplexa) species isolated from the faeces of 10 reptilian and three raptorial bird hosts in attempt to test heteroxenous life cycle pattern. Only three reptilian isolates originated from viperid snakes, namely from Calloselasma rhodostoma, Atheris nitschei and Vipera ursinii induced lethal dermal caryosporosis in SCID mice. Neither clinical signs nor developmental stages were observed in mice infected with further nine caryosporan isolates originated from other reptilian and raptorial bird hosts. Results of this study confirmed that SCID mice represent a useful tool for evaluation of heteroxenous life cycle pattern of caryosporan coccidia and that only the Caryospora species from viperid and crotalid snakes produce dermal caryosporosis in mice