Population-based analyses of Giardia duodenalis is consistent with the clonal assemblage structure
1 National Institute of Public Health and Environment (RIVM), Laboratory for Zoonosis and Environmental Microbiology (CIb-LZO), P.O. Box 1, 3720, BA, Bilthoven, The Netherlands
2 Department of Parasitology, Laboratory of Public Health, Haarlem, The Netherlands
3 Josephine Bay Paul Center for Comparative Evolution and Molecular Biology, Woods Hole, MA, USA
4 Department of Diagnostics and Vaccinology, Swedish Institute for Communicable Disease Control, Solna, Sweden
5 Department of Infectious, Parasitic, and Immunomediated Diseases, Istituto Superiore di Sanita, Rome, Italy
Parasites & Vectors 2012, 5:168 doi:10.1186/1756-3305-5-168Published: 10 August 2012
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. 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.
Population genetic analyses on the single and multiple-locus level on an extensive dataset of G. duodenalis isolates from humans and animals were performed.
Our 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.
We 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.