Study of intra-species diversity in Giardia intestinalig Assessment of a genotype distribution in isolated islands of Indonesia

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We aimed to determine the status of intra-species genetic diversity of Giardia intestinalis and the factors that contribute to the maintenance of population diversity in this species. Giardia samples collected from various mammals (dog, pig, mouse and human) i n different geographical sites(Indonesia, Nepal and Japan) were analyzed using multilocus markers (18S small subunit ribosomal RNA, glutamate dehydrogenase and triosephosphate isomerase genes). In the human samples, various sub-genotypes within assemblage A and/or B were clearly classified ; however, no site-specific distribution of genotypes was observed. We also confirmed that assemblages C and D, which have been recognized as dog-specific genotypes, were present in a few human samples in a rural area of Indonesia. A comparison of the determined sequences of human and animal isolates collected at the same site specifically confirmed the presence of each sub-assemblage cluster within assemblage B.Taken together with previous indications of assemblage-level host specificities in G. intestinalis, these results demonstrate that host specificities could be partly responsible for the assemblage levels of genetic polymorphism in this pathogen, however the diversity within each assemblage especially assemblage B seemed not in the case. Although the present geographical distributions and isolations of the pathogen were not thought to be a driving force of its genetic diversity since the distribution did not indicate any locality, we showed here the possibility that niche separations in a site might be related to the diversity formation. Niche separation may enable Giardia to accumulate the unique mutations in the genome and maintain novel diversity within the clonal population.