Detection and genotyping of Cryptosporidium from brown rats (Rattus norvegicus) captured in an urban area of Japan.

We investigated the prevalence and genotypes of Cryptosporidium parasite in 50 brown rats (Rattus norvegicus) inhabiting an urban area of Japan. Fecal samples collected from the animals were examined by an immuno-fluorescence assay (IFA). Genomic DNA was extracted directly from fecal sample of each animal and nested PCR was performed to amplify part of the 18S ribosomal RNA (18SrRNA) of the Cryptosporidium species. The detection rate was 8% by IFA and 38% by nested PCR. The sequence and phylogenetic analyses of 13 PCR products showed that the Cryptosporidium from brown rats were clustered into four distinct genotypes. Interestingly, one of the four genotypes was significantly distinct from the C. parvum and C. hominis genotypes. Our results suggest the existence of a new genotype of Cryptosporidium in brown rats.