May 2009

Document Type


Degree Name



Dept. of Public Health and Preventive Medicine


Oregon Health & Science University


We conducted a prospective cohort study among 477 Peruvian children to assess the frequency of, and risk factors for, infections with Giardia, Cryptosporidium and Cyclospora. We also sought to determine if Giardia infections within 60 days of enrollment into the study affected the incidence of Cyclospora or Cryptosporidium infections. One-hundred sixty (33.5%) of children had Giardia infection within the first sixty days of observation, and 381 (79.5%) had at least one infection during the five-year study. The median episode length was less than seven days, however, ten percent of infections lasted longer than one year. Results from the Cox proportional hazards analysis showed that Giardia increased the child’s risk for acquiring subsequent infections with Crypsporidium (HR 5.49, 95% CI 2.74 – 11.0) or Cyclospora, though risk differed by sanitation status for Cyclospora (with toilet HR 1.12 95% CI 0.69-1.80, without toilet HR 2.22 95% CI 1.68-2.94). Antiparasitic treatment of Giardia did not affect the risk for later infection with Cyclospora or Cryptosporidium. These findings suggest that Giardia may predispose children to subsequent infections with Cryptosporidium or Cyclospora, however, further research into specific risk factors such as specific foods, their sources, and other socioeconomic risk factors may help elucidate the relationships between these parasites.




School of Medicine



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