2004 Outbreak of E.Coli O157:H7 at a North Carolina State Fair Petting Zoo

 

Speaker:                     Brant Goode, BSN/RN, MPH

Epidemic Intelligence Service Officer

CDC, assigned to NC Div of Public Health

 

Level of Knowledge:  Multi-Level

 

Long Abstract:

Background: E. coli O157:H7 and other enterohemorrhagic E. coli (EHEC) infections cause hemorrhagic colitis and hemolytic uremic syndrome (HUS). An estimated 73,000 EHEC related infections and 61 deaths occur annually in the United States. Contaminated foods, beverages, water and livestock contact have caused outbreaks. In 2004, an E. coli O157:H7 outbreak occurred among North Carolina State Fair visitors.

Methods: We conducted a matched case-control study among fair visitors using randomly recruited controls who purchased tickets in advance. We defined cases as persons with culture-confirmed E. coli O157:H7 infection, HUS, or bloody diarrhea with illness onset after visiting the fair. Clinical specimens and environmental samples were tested by culture and pulsed-field gel electrophoresis (PFGE).

Results: Of 108 reported cases, we enrolled 45 confirmed or probable case-patients and 188 controls in the case-control study. Median case-patient age was 3.2 years (range: 1-61). Thirty-six case-patients (80%) reported visiting the same petting zoo (Odds Ratio [OR]:7.7, 95% Confidence Interval [CI]:3.5-17.0). Among visitors to this petting zoo, illness was associated with stepping in or touching manure (OR: 4.9, CI: 1.9-12.8), falling or sitting on the ground (OR: 3.4, CI: 1.3-8.6) or contact with sheep or goats’ front legs (OR: 2.5, CI: 1.03-5.9).  Hand hygiene upon exiting the petting zoo was not protective (OR: 1.7, CI: 0.5-5.8). Of 38 patient isolates, 33 (87%) had indistinguishable PFGE patterns. Environmental isolates from the petting zoo area were indistinguishable by PFGE from these 33 clinical isolates.

Conclusions: In this study, most illnesses were associated with animal or manure contact in a single petting zoo. Hand hygiene was not protective. Contact with animals and manure in petting zoos should be restricted to prevent EHEC infections.

Keywords:

  • Escherichia coli O157:H7
  • EHEC
  • hemolytic uremic syndrome
  • petting zoo
  • zoonosis

 

Learning Objectives:

 

  1. Describe hazards associated with animal contact in fairs and petting zoos with a focus on E. coli O157:H7
  2. Describe difficulties involved in site remediation once contamination is recognized.
  3. Describe prevention measures to prevent human exposure and site contamination.