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Epidemiology:
2000 Annual Conference of the ISEE

ENVIRONMENTAL RISK FACTORS FOR PRESENCE OF CRYPTOSPORIDIUM PARVUM ANTIBODIES IN HUMAN SERUM

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ENVIRONMENTAL RISK FACTORS FOR PRESENCE OF CRYPTOSPORIDIUM PARVUM ANTIBODIES IN HUMAN SERUM ELIZABETH HILBORN, FROST FLOYD, MULLER T, CALDERON REBECCA. US EPA. EMail: hilborn.e@epa.gov

Background - Cryptosporidium parvum is a parasite that infects a variety of vertebrate hosts. Sources of infection include contaminated raw produce and drinking water. Outbreaks of foodborne and waterborne infection are infrequently reported, yet serological evidence suggests that infection may commonly occur. Methods - We analyzed serum and data gathered from a convenience sample of National Health and Nutrition Examination Survey III participants to identify risk factors for the presence of anti-cryptosporidial antibodies. Seropositivity was defined as: those samples determined to contain IgG antibodies to 15/17 kDa proteins by the enzyme-linked immunoelectro-transfer blot assay with an intensity of response greater than 10% of a positive control. Data were characterized by univariate analysis. Bivariate statistical analysis and logistic regression modeling were used to determine the association between gender, age, race, city of residence, salad and water consumption, serum carotenoids (biomarkers of exposure to produce), pet ownership, antacid and bottled water usage, home water source, and seropositivity. Results - Of 1356 participants, 558 (41%) were seropositive. Persons resided in seven cities and ranged in age from 1–90 years (median: 38 years); 50% were female, 50% white race, 25% African-American race, and 22% Hispanic ethnicity. Seropositivity varied by city (range: 29% - 57%). Older participants were significantly more likely to be seropositive (trend p< 0.0001). The full regression model included gender, age, race, city, and serum alpha-carotene, all significantly associated with seropositivity; inclusion of an increased water consumption variable in the model improved the fit, but was not statistically significant (p=0.09). No other variables listed above were significantly associated with seropositivity. Conclusion - These data suggest that significant differences in seropositivity exist among populations of different cities, and that prevalence of seropositivity increases with age. Increased serum alpha-carotene is significantly associated with seropositivity. Although serum alpha-carotene levels have been correlated with consumption of produce, the biomarker is not specific to the raw produce items which may be potential vehicles for oocysts. Although exposure to municipal water (by city) and serum alpha-carotene appear to be independent risk factors for seropositivity, unmeasured differences in food consumption, behavior, or cultural practices among persons living in various geographic areas may contribute to these findings. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

© 2000 Lippincott Williams & Wilkins, Inc.

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