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United States Department of Agriculture

Agricultural Research Service

Title: Outbreak of Escherichia coli 0157:H7 Associated with Attencdance at a Large Livestock Exhibition - Denver, Colorado, January-February 2009

item Comstock, Nicole
item Maguire, Hugh
item Bronken, Abby
item Mcdonald, Carol
item Hite-bynum, Donna
item Cichon, Mary Kate
item Durso, Lisa

Submitted to: Proceedings of the International Conference on Emerging Infectious Diseases
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2010
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Colorado Department of Public Health and Environment, several Denver metropolitan area public health departments, and the United States Department of Agriculture Agricultural Research Service investigated an outbreak of Escherichia coli O157:H7 (E. coli O157:H7) that occurred in January-February 2009 in the Denver area. Thirty cases were identified, including 29 laboratory-confirmed cases with matching pulsed-field gel electrophoresis (PFGE) patterns from stool specimen isolates and one probable case. The outbreak investigation consisted of case finding and interviews, two separate case-control studies, an environmental investigation, and laboratory testing. The results of this investigation indicate that exposure to animals at a large livestock exhibition was the likely cause of the outbreak; specifically, contact with animals in the children's education area. Recommendations were provided to the exhibition organizers to attempt to prevent this type of outbreak from occurring in the future.

Technical Abstract: Outbreak of Escherichia coli O157:H7 associated with attendance at a large livestock exhibition – Denver, Colorado, January-February 2009 Nicole Comstock1, Hugh Maguire1, Abby Bronken2, Carol McDonald3, Donna Hite-Bynum4, Mary Kate Cichon1, Lisa Durso5 1 Colorado Department of Public Health and Environment 2 Denver Environmental Health 3 Denver Public Health 4 Tri-County Health Department 5 United States Department of Agriculture, Agricultural Research Service Background Escherichia coli O157:H7 (ECO157) is an important cause of gastrointestinal illness and outbreaks have been associated with animal settings such as livestock exhibitions and petting zoos. In January and February 2009, the Denver area experienced an increase in the number of reported ECO157 cases, many of which reported attending a large livestock exhibition prior to symptom onset. Methods To determine the source of infection, we conducted two case-control studies (Study I and II), an environmental investigation, and laboratory testing. Study I examined if attending the exhibition was associated with illness. Attempts were made to enroll two age- and neighborhood-matched controls per case. Study II examined specific exhibition exposures and behaviors to determine risk factors associated with illness. Two age-matched exhibition attendee controls were enrolled per case. An environmental investigation at the exhibition site was conducted to collect environmental samples, which were analyzed at state and federal laboratories. Results In total, 29 laboratory-confirmed ECO157 cases with matching pulsed-field gel electrophoresis (PFGE) patterns and one probable case were identified in Denver area residents. The median age of cases was five years, and 77% of cases were female. One case who attended the exhibition attended a child care center while ill and was the likely source of a secondary outbreak at the center. Study I found that attendance at the exhibition was associated with illness (OR=undefined, p=<0.0001). Study II found that visiting the exhibition’s children’s area was associated with illness (OR=undefined, p=0.04). Touching a cow, goat, or pig displayed in this area was significantly associated with illness. Environmental samples collected from the children’s area were positive for ECO157 and matched the outbreak PFGE patterns. Conclusion The likely cause of this outbreak was contact with animals displayed in the exhibition’s children’s area. This area was not a designated petting zoo, but direct contact with animals such as cows, goats, and pigs was encouraged. Disease prevention measures, such as readily accessible handwashing stations, were not provided in this area. To reduce the risk for disease transmission associated with animals in public settings, appropriate prevention measures should be taken regardless of whether the setting is a defined petting zoo or other type of animal contact area.

Last Modified: 10/16/2017
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