Authors

Discussion

It is unclear why developed countries are still at risk of giardiasis despite their high health standards. In this study, we describe the epidemiology of giardiasis and identify modifiable risk factors associated with giardiasis in south western Sydney, Australia. A retrospective 1:3 unmatched case-control study of confirmed giardiasis cases notified to the South Western Local Health District Public Health Unit between January 2011 and August 2016 was used to investigate giardiasis. Three groups of controls, neighbourhood, friend and pertussis controls selected from the same health district were included to increase response rate and reduce selection bias. Demographic, clinical and potential risk factor data was collected from both cases and controls through contact with mail and telephone.  This study revealed that giardiasis is significantly associated with swimming in pools, contact with domestic animals, wildlife or livestock and with those who visited their country of birth (or their parent’s country of birth). Males, younger children and working adults were the most at-risk groups and the vast majority of these giardiasis cases were acquired locally rather than imported from overseas countries. Unexpectedly, residents living in urban settings were associated with an increased giardiasis risk. This study emphasised the need to identify risk factors for giardiasis and the importance of surveillance and control strategies.