Longitudinal study of Giardia lamblia infection in a day care center population.

An enzyme-linked immunosorbent assay was used to detect Giardia lamblia in stool specimens collected during a 15-month longitudinal study of diarrhea in 82 children 1 to 24 months old attending a day care center (DCC) in Houston. A total of 2727 stool specimens were collected on a weekly basis from the DCC children and were evaluated for rotavirus and Giardia. For DCC children who developed diarrhea stool specimens were also cultured for bacterial enteropathogens. During the 15-month study period, 48 episodes of Giardia infection were detected in 27 of 82 (33%) DCC children, compared with 57 episodes of rotavirus detected in 37 (45%) of these same DCC children. The duration of Giardia excretion was 2.0 +/- 1.5 weeks (mean +/- SD). Only 6 (7%) of the 82 DCC children, or 6 of the 27 (22%) with infection, developed symptoms attributable to Giardia. Ten of the 27 (37%) DCC children infected with Giardia had 2 or more episodes of infection. Giardia was identified in the DCC in all months except June. Two Giardia outbreaks occurred in 1 of the 6 DCC rooms under study. One outbreak was associated with overcrowding. Neither outbreak was associated with the introduction of a new Giardia-positive child into the involved room. In this study Giardia infection occurred commonly in the DCC throughout the year, was rarely associated with illness and was not associated with introduction of asymptomatic carriers into the DCC rooms.