Giardiasis

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Rates presented are per 100,000 population and are based on the U.S. 2000 Census.

Giardiasis is a flagellate protozoan infection most commonly transmitted by ingestion of cysts from fecally contaminated water. The infection can also be transmitted by person-to-person and hand-to-mouth transfer of cysts from the feces of infected individuals.

There were 515 cases of giardiasis reported in 2000, a 21% decrease over 1999 (Figure Gi1). This was also lower than average number of cases from the previous four-year period 1996-1999 (776 cases/year).  The number of reported cases was highest during the mid-summer and early autumn months (Figure Gi2). The increase during warm weather months may indicate increased exposure to contaminated surface water during outdoor activities.

There was no difference in incidence between males and females. Age-specific rates were highest among children age 1-4 (37.8) followed by children under age 1 (18.9), which may be due to the increased risk of transmission in day-care centers (Figure Gi3). Nationally, outbreaks of giardiasis have been occurring more frequently in day-care centers. Transmission in day-care centers can be avoided through good handwashing practices and exclusion of children with diarrhea. People of races other than white or black had a higher case rate (6.0) than either blacks (2.7) or whites (5.2). This may reflect the increasing trend of overseas adoption and continued immigration.

Among counties with at least 5 cases reported, the incidence rates were highest in Bartholomew (39.2), DeKalb (32.3), Decatur (24.4), Whitley (22.8) and Randolph (18.3) Counties.  No outbreaks of giardiasis were reported in Indiana in 2000.

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Footnotes

1 - Race was unknown for 209 of the reported cases.

2 - "Other" includes American Indian/Alaska Native, Asian, Native Hawaiian/Pacific Islander, and multiracial.

3 - Sex was unknown for 9 of the reported cases.

* - Rate based on less than 20 cases and should be considered unstable.

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