Sequence and PCR-RFLP analysis of the internal transcribed spacers of the rDNA repeat unit in isolates of Cryptosporidium from different hosts

The Cryptosporidium ITS1, 5.8S and ITS2 rDNA regions from a number of Crypt osporidium isolates from different hosts and geographical areas were cloned and sequenced in order to investigate the extent of sequence heterogeneity between human and cattle-derived isolates from different geographical loca tions and also between isolates of Cryptosporidium from different hosts suc h as cats, pigs, mice and a koala. Calf-derived isolates from different con tinents were virtually identical as were human-derived isolates from the UK and Australia. Genetic differences between Cryptosporidium isolates were e xtensive and were in fact greater than the level of nucleotide divergence b etween Toxoplasma gondii and Neospora caninum rDNA sequences. Based on the sequence information derived from this study, PCR-RFLP of the ITS1 region w as undertaken in order to directly amplify and genotype Cryptosporidium iso lates from different hosts. This PCR-RFLP approach can now be used for mole cular epidemiology studies, circumventing the need for costly sequencing an d allowing a wider range of genetically different isolates to be examined.