The Cryptosporidium ITS1, 5·8S and ITS2 rDNA regions
from a number of Cryptosporidium 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 locations
and also between isolates of Cryptosporidium from
different hosts such as cats, pigs, mice and a koala. Calf-derived isolates
from different continents were virtually identical
as were human-derived isolates from the UK and Australia. Genetic differences
between Cryptosporidium isolates were
extensive and were in fact greater than the level of nucleotide divergence
between Toxoplasma gondii and Neospora caninum
rDNA sequences. Based on the sequence information derived from this study,
PCR–RFLP of the ITS1 region was
undertaken in order to directly amplify and genotype Cryptosporidium
isolates from different hosts. This PCR–RFLP
approach can now be used for molecular epidemiology studies, circumventing
the need for costly sequencing and allowing
a wider range of genetically different isolates to be examined.