title: Giardia spp. Are Commonly Found in Mixed Assemblages in Surface Water, as Revealed by Molecular and Whole-Genome Characterization.
abstract: Giardia is the most common parasitic cause of gastrointestinal infections worldwide, with transmission through surface water playing an important role in various parts of the world. Giardia duodenalis (synonyms: G. intestinalis and G. lamblia), a multispecies complex, has two zoonotic subtypes, assemblages A and B. When British Columbia (BC), a western Canadian province, experienced several waterborne giardiasis outbreaks due to unfiltered surface drinking water in the late 1980s, collection of isolates from surface water, as well as from humans and beavers (Castor canadensis), throughout the province was carried out. To better understand Giardia in surface water, 71 isolates, including 29 from raw surface water samples, 29 from human giardiasis cases, and 13 from beavers in watersheds from this historical library were characterized by PCR. Study isolates also included isolates from waterborne giardiasis outbreaks. Both assemblages A and B were identified in surface water, human, and beavers samples, including a mixture of both assemblages A and B in waterborne outbreaks. PCR results were confirmed by whole-genome sequencing (WGS) for one waterborne outbreak and supported the clustering of human, water, and beaver isolates within both assemblages. We concluded that contamination of surface water by Giardia is complex, that the majority of our surface water isolates were assemblage B, and that both assemblages A and B may cause waterborne outbreaks. The higher-resolution data provided by WGS warrants further study to better understand the spread of Giardia.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada British Columbia Public Health Microbiology and Reference Laboratory, Provincial Health Services Authority, Vancouver, BC, Canada natalie.prystajecky@bccdc.ca.
authors.forename: Natalie
authors.initials: N
authors.lastname: Prystajecky
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Clement K-M
authors.initials: CK
authors.lastname: Tsui
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada British Columbia Public Health Microbiology and Reference Laboratory, Provincial Health Services Authority, Vancouver, BC, Canada.
authors.forename: William W L
authors.initials: WW
authors.lastname: Hsiao
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Miguel I
authors.initials: MI
authors.lastname: Uyaguari-Diaz
authors.affiliation: British Columbia Public Health Microbiology and Reference Laboratory, Provincial Health Services Authority, Vancouver, BC, Canada.
authors.forename: Jordan
authors.initials: J
authors.lastname: Ho
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada British Columbia Public Health Microbiology and Reference Laboratory, Provincial Health Services Authority, Vancouver, BC, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tang
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada British Columbia Public Health Microbiology and Reference Laboratory, Provincial Health Services Authority, Vancouver, BC, Canada.
authors.forename: Judith
authors.initials: J
authors.lastname: Isaac-Renton
mesh_terms: D001955:British Columbia; D005618:Fresh Water / Q000469:parasitology*; D018503:Genome, Protozoan; D005838:Genotype; D016829:Giardia lamblia / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D005873:Giardiasis / Q000469:parasitology; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction