Giardiasis in NSW: Identification of Giardia duodenalis assemblages contributing to human and cattle cases, and an epidemiological assessment of sporadic human giardiasis A.J. Asher ⁎, G. Hose, M.L. Power Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia abstract article info Article history: Received 11 September 2015 Received in revised form 19 June 2016 Accepted 27 June 2016 Available online 29 June 2016 Two genetic assemblages (A and B) of the protozoan parasite species, Giardia duodenalis, infect humans, domestic animals and wildlife. In New South Wales, Australia, over 2000 sporadic human giardiasis cases are reported an- nually, but parasite sources and links between sporadic cases are unknown. This study describes G. duodenalis as- semblages contributing to human and cattle cases in NSW, and examines demographic, spatial, and temporal distributions of NSW human infections and G. duodenalis assemblages. Genotyping by PCR-restriction fragment length polymorphism of the glutamate dehydrogenase (gdh) gene identified G. duodenalis assemblage B as the most common (86%) cause of infection among human cases (n = 165). Approximately 37% of cattle DNA samples were PCR positive (18S rRNA, gdh), and G. duodenalis assemblages E (69%) or B (31%) were identified from these samples. Human assemblage A was more common among older age groups, and seasonality in the geographic dispersal of human assemblage A was observed. The results of this study indicate G. duodenalis assemblage B is highly prevalent among humans in NSW, and the potential for cross-species transmission exists between humans and cattle in this region. Spatio-temporal and demographic distributions of human assemblage A and B are highlighted, and risk factors associated with these dispersal patterns warrants further research. © 2016 Elsevier B.V. All rights reserved. Keywords: Giardia duodenalis Assemblages Humans Cattle New South Wales 1. Introduction Giardiasis is one of the most common communicable gastrointesti- nal diseases of humans and domestic animals worldwide (Ignatius et al., 2012). The aetiological agent, Giardia duodenalis (syn. Giardia intestinalis, Giardia lamblia), is a protozoan parasite of mammals and is transmitted via the faecal-oral route (Caccio and Ryan, 2008). Eight G. duodenalis genetic assemblages (A to H) infect a wide range of mamma- lian host groups, including humans, domestic animals and wildlife (Andrews et al., 1989; c.f. Caccio and Ryan, 2008; Monis et al., 2003; Lasek-Nesselquist et al., 2010). Humans are only infected by G. duodenalis assemblages A and B which are zoonotic, and most likely rep- resent two separate species of Giardia (Thompson and Monis, 2012). Livestock, companion animals and wildlife are infected by assemblages A and B, and also host specific assemblages C to H (Monis et al., 2003; Lasek-Nesselquist et al., 2010). In Australia, human giardiasis is largely a sporadic disease and over- all prevalence is estimated between 2 and 7% (Thompson and Monis, 2012). In New South Wales over 2000 human cases have been reported each year since 2009 (NSW Health Notifiable Conditions Information Management System, 2015). On-going disease surveillance shows a steady increase in the number of human giardiasis cases reported each year, with the incidence (per 100,000 population) rising from 13.0 to 27.6 over a 10 year period (NSW Department of Health, 2011; NSW Department of Health, 2013). The increasing giardiasis incidence has highlighted Giardia as an emerging public health concern. Demographic and temporal distributions of sporadic human giardia- sis among residents in NSW are similar to patterns observed in other de- veloped nations (Centres for Disease Control and Prevention, 2012). Sources of sporadic infection in NSW communities, however, are largely unknown. It is unclear if associations between high risk age groups and giardiasis transmission exist, or whether fluctuations in notification rates across NSW reflect different disease dynamics. For example, prev- alence of Giardia among wild and captive animals in Australia ranges from 3% to 29% (Cox et al., 2005; Ng et al., 2011; Nolan et al., 2013), and high rates (58%) of Giardia positivity have been previously reported from cattle in Western Australia (O'Handley et al., 2000). Zoonotic as- semblages A and B have been identified in wildlife and domestic ani- mals (Ng et al., 2011; Nolan et al., 2013; Vermeulen et al., 2015), and these could be contributing to transmission between humans and non-human hosts. The purpose of this study was to examine G. duodenalis assemblages contributing to infection among humans in NSW; and to investigate Infection, Genetics and Evolution 44 (2016) 157–161 ⁎ Corresponding author. E-mail address: amy.asher@mq.edu.au (A.J. Asher). http://dx.doi.org/10.1016/j.meegid.2016.06.051 1567-1348/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Infection, Genetics and Evolution journal homepage: www.elsevier.com/locate/meegid