RESUMEN
In the summer of 1995, cryptosporidiosis was diagnosed in a child in hospital. This child had taken part in a summer activity project involving 161 children and nine adults. Reports of a similar illness among a number of other participants prompted an outbreak investigation. A cohort study was conducted in two phases. Thirteen children (aged 6 to 15 years) out of 161 respondents to the first questionnaire met the case definition for illness and cryptosporidium was detected in stools from seven of the 13. Illness was significantly associated with child participants who had visited an open farm (p < .000005). Nine of the cases sought medical attention, and two were admitted to hospital. The second phase of the cohort study was conducted among 52 of the 55 people who had visited the open farm. Illness was significantly associated with playing in sand to which animals had access, at the edge of a stream beside a picnic area (p < .005). Contact with various animals was not associated with illness. This outbreak emphasises the risk for children of visiting open farms. Managers of open farms need to be aware of the potential for transmission of infectious diseases to visiting children. Strict implementation of hygiene measures is essential to minimise risk.
