Large sequence variation at two microsatellite loci among zoonotic (genotype C) isolates of Cryptosporidium parvum

The genetic polymorphism among 57 Cryptosporidium parvum isolates belonging to genotype 'C' was studied by PCR amplification and the sequencing of two microsatellite loci (ML1 and ML2). A comparative analysis of DNA sequences showed the presence of three (ML1-238, ML1-226, and ML1-220) and seven (ML 2-231, ML2-229, ML2-227, ML2-213. ML2-193, ML2-191, and ML2-187) different alleles at these two loci. Alleles differed by expansions/contractions of t he microsatellite repeats that generated length polymorphisms. Some alleles were found to be associated with infections of all examined hosts (calf, k id, lamb, and human), whereas others were either associated with a single h ost, or were geographically restricted. When considering the information fr om both loci, some preferential associations between alleles are apparent. These data confirm the utility of microsatellite markers for the molecular identification of C. parvum, which is of particular relevance in the invest igation of the source of infection of outbreaks and single cases, its well as for genetic studies. (C) 2001 Australian Society for Parasitology Inc. P ublished by Elsevier Science Ltd. All rights reserved.