Abstract
BackgroundGiardia duodenalis is a common protozoan parasite of humans and animals. Genetic characterization of single loci indicates the existence of eight groups called assemblages, which differ in their host distribution. Molecular analyses challenged the idea that G. duodenalis is a strictly clonal diplomonad by providing evidence of recombination within and between assemblages. Particularly, inter-assemblage recombination events would complicate the interpretation of multi-locus genotyping data from field isolates: where is a host infected with multiple Giardia genotypes or with a single, recombined Giardia genotype.MethodsPopulation genetic analyses on the single and multiple-locus level on an extensive dataset of G. duodenalis isolates from humans and animals were performed.ResultsOur analyses indicate that recombination between isolates from different assemblages are apparently very rare or absent in the natural population of Giardia duodenalis. At the multi-locus level, our statistical analyses are more congruent with clonal reproduction and can equally well be explained with the presence of multiple G. duodenalis genotypes within one field isolate.ConclusionsWe conclude that recombination between G. duodenalis assemblages is either very rare or absent. Recombination between genotypes from the same assemblage and genetic exchange between the nuclei of a single cyst needs further investigation.
Highlights
Giardia duodenalis is a common protozoan parasite of humans and animals
One 551-bp glutamate dehydrogenase (GDH) sequence (GQ337967) in GenBank displayed a recombination event, where the last ~95 bp did not align with any other G.duodenalis, but were similar to H. sapiens RIO kinase 2 (AK225348) [36]
No inter-assemblage recombination was identified in the GDH sequences of the K4016 and SweCat17 isolates
Summary
Giardia duodenalis is a common protozoan parasite of humans and animals. Genetic characterization of single loci indicates the existence of eight groups called assemblages, which differ in their host distribution. Inter-assemblage recombination events would complicate the interpretation of multi-locus genotyping data from field isolates: where is a host infected with multiple Giardia genotypes or with a single, recombined Giardia genotype. G. lamblia, G. intestinalis) is the etiological agent of giardiasis, a gastrointestinal infection of humans, companion animals, livestock and wildlife. Symptoms of a G. duodenalis infection range from asymptomatic to severe diarrhea as well as chronic disease [1]. G. duodenalis has a simple life cycle comprising rapidly multiplying, non-invasive trophozoites on the mucosal surface of the intestine, and the production of environmentally resistant cysts that are shed with the host faces. G. duodenalis is considered as a species complex, whose members
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