Outbreak ofEscherichia coliO157:H7 Related to Animal Contact at a Petting Zoo

Abstract

OBJECTIVE: To determine the cause of an outbreak ofEscherichia coli0157:H7 related to animal exposures so that further transmission could be prevented.DESIGN: Description of laboratory investigations and a case control study.SETTING: Agricultural pavilion at an annual fair in Ontario.POPULATION: People with laboratory evidence ofE coli0157:H7 (seven people) and others with diarrhea (155 people) who called the health unit following a media release were interviewed. Animals that were accessed most frequently by the public in the agriculture pavilion were tested forE coli0157:H7. In the case control study, a case was defined as someone with laboratory-confirmedE coli0157:H7, or someone who developed severe or bloody diarrhea two to eight days after attending the agricultural pavilion at the fair (61 people). A convenience sample of people who attended the agricultural pavilion but did not develop diarrhea was selected as the control group (89 people).INTERVENTIONS: Human and animalE coli0157:H7 specimens were subtyped. Cases and controls were interviewed using a standardized questionnaire.RESULTS: Subtyping of the seven human isolates ofE coli0157:H7 revealed five that were of an extremely uncommon phage type. Three samples from goats and one from sheep at the petting zoo in the agricultural pavilion were of this same phage type. The case control study also implicated goats (odds ratio [OR] 3.65; 95% CI 1.63 to 8.52) and sheep (OR 2.94; 95% CI 1.33 to 6.57) from the petting zoo.CONCLUSIONS: Results of this investigation suggest strongly that the goats and sheep from the petting zoo were the source of this outbreak ofE coli0157:H7.