Giardia outbreaks can occur in communities where water supplies become contaminated with raw sewage. It can be contracted by drinking water from lakes or streams where water-dwelling animals such as beavers and muskrats, or where domestic animals such as sheep, have caused contamination. All travelers are at some risk of acquiring infection, but hikers drinking untreated surface water have the highest risk. The incidence of known cases is approximately 2 out of 10,000 people. It has been on the increase in the last few years.
Some infections resolve on their own.
Anti-infective agents such as metronidazole or quinacrine may be used. Furazolidone is generally used to treat children. Drug resistance may be a factor in treatment failures, requiring a change in antibiotic therapy. In pregnancy , treatment should be deferred until after delivery because none of the drugs used to treat the infection are approved for use in pregnancy. Spontaneous resolution is common, but persistent infections have been reported.