GiardiaandCryptosporidiumantibody prevalence and correlates of exposure among Alaska residents, 2007–2008

Giardia duodenalisandCryptosporidiumspp. are common intestinal protozoa that can cause diarrhoeal disease. Although cases of infection withGiardiaandCryptosporidiumhave been reported in Alaska, the seroprevalence and correlates of exposure to these parasites have not been characterised. We conducted a seroprevalence survey among 887 residents of Alaska, including sport hunters, wildlife biologists, subsistence bird hunters and their families and non-exposed persons. We tested serum using a multiplex bead assay to evaluate antibodies to theGiardia duodenalisvariant-specific surface protein conserved structural regions and to theCryptosporidium parvum17- and 27-kDa antigens. Approximately one third of participants in each group had evidence of exposure toCryptosporidium. Prevalence ofGiardiaantibody was highest among subsistence hunters and their families (30%), among whom positivity was associated with lack of community access to in-home running water (adjusted prevalence ratio [aPR] 1.15, 95% confidence interval (CI) 1.02–1.28) or collecting rain, ice, or snow to use as drinking water (aPR 1.09, 95% CI 1.01–1.18). Improving in-home water access for entire communities could decrease the risk of exposure toGiardia.