title: Population-based analyses of Giardia duodenalis is consistent with the clonal assemblage structure.
abstract: BACKGROUND
  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.
  
  
  METHODS
  Population genetic analyses on the single and multiple-locus level on an extensive dataset of G. duodenalis isolates from humans and animals were performed.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Takumi
authors.forename: Arno
authors.initials: A
authors.lastname: Swart
authors.forename: Theo
authors.initials: T
authors.lastname: Mank
authors.forename: Erica
authors.initials: E
authors.lastname: Lasek-Nesselquist
authors.forename: Marianne
authors.initials: M
authors.lastname: Lebbad
authors.forename: Simone M
authors.initials: SM
authors.lastname: Cacciò
authors.forename: Hein
authors.initials: H
authors.lastname: Sprong
mesh_terms: D014644:Genetic Variation; D005838:Genotype; D016829:Giardia lamblia / Q000145:classification* / Q000235:genetics*; D015810:Linkage Disequilibrium; D010802:Phylogeny; D011995:Recombination, Genetic