Molecular epidemiology of Giardia duodenalis in Australia

This study investigates Giardia duodenalis contributing to sporadic clinical cases in NSW between 2010 and 2013, and to cases among children of a high prevalence remote Indigenous community. The study also developed and evaluated two new molecular screening tools, terminal-restriction fragment length polymorphism (T-RFLP) and multilocus next generation sequencing for Giardia identification. In NSW, G. duodenalis assemblage B was highly prevalent, and patients aged 0 – 39 years were most at risk. Subtyping showed cases were highly similar (BIV). Spatial mapping demonstrated seasonal links in the geographic dispersal of assemblage A across NSW. High Giardia carriage rates (64.9%) were detected among remote Indigenous children, and over 50% of cases were not detectable by microscopy. A variety of assemblages, subassemblages/genotypes persisted in the community over a 12 month period, and these assemblages and subassemblages were not linked to child age or gender. Mixed assemblage B population infections were higher among remote community children than children in NSW. Application of T-RFLP and multilocus NGS to community studies enabled powerful detection of Giardia, and deep population analyses of individual cases. The study significantly progresses knowledge of Giardia transmission in NSW, and among remote community children, and has facilitated new approaches to Giardia research.