Outbreaks of Escherichia coli O157:H7 Associated with Petting Zoos - North Carolina, Florida, and Arizona, 2004 and 2005

Editorial Note

E. coli O157:H7 causes approximately 73,000 illnesses in the United States annually, leading to an estimated 2,168 hospitalizations and 61 deaths.^[1] HUS is a principal cause of acute renal failure among children in the United States and occurs in 3%-7% of E. coli O157:H7 infections.^[2] Among patients with HUS, approximately 3%-5% die as a result.^[2] Most cases of diarrhea-associated HUS are caused by STEC, of which E. coli O157:H7 has the strongest association with HUS worldwide.^[3] At least 80% of childhood HUS is attributable to infection with STEC, primarily E. coli O157:H7.^[4]

The primary animal reservoir for E. coli O157:H7 is ruminant livestock, which are asymptomatically colonized. The primary route of transmission for E. coli O157:H7 is foodborne; however, among 350 E. coli O157:H7 outbreaks reported in the United States during 1982-2002, the transmission route for 11 (3%), accounting for 319 cases, was animal contact.^[5] The three E. coli O157:H7 outbreaks described in this report, accounting for 173 cases and associated with direct and indirect animal contact at petting zoos, emphasize the need for adequate control measures to reduce zoonotic transmission.

In the North Carolina outbreak, extensive direct animal contact occurred in an area contaminated with manure. In the Florida outbreak, illness was associated with touching and feeding animals and indirect animal contact (e.g., touching sawdust or shavings or visibly soiled clothes or shoes). In the Arizona outbreak, at least one case likely resulted from exposure in the play area adjacent to the petting zoo, where contamination via drainage from the petting zoo was suspected. In certain instances, exposure to E. coli O157:H7 might have occurred before petting zoo patrons could practice hand hygiene. Also, exposure from contaminated clothes, shoes, strollers, or other fomites might have occurred before or after hand-hygiene practice.

Experience from these and previous outbreaks^[6,7] underscores the necessity of using sensitive laboratory isolation methods, such as those used in these outbreaks, for detecting E. coli O157:H7 from livestock feces and agricultural environmental samples. Had direct plating methods used for human stool been the only method used to recover E. coli O157:H7 from environmental samples, many positive specimens would have been undetected. Because of the multiple, competing microorganisms in livestock fecal material and soil, selective culture conditions, including selective broth enrichment, immunomagnetic separation, and plating on selective media, should be used.^[6]

In 2001, CDC issued guidelines to reduce the risk for transmission of enteric pathogens at venues where the public has contact with animals.^[8] In March 2005, the National Association of State Public Health Veterinarians (NASPHV) published recommendations on hand washing, venue design, animal care and management, and risk communication regarding disease transmission for staff and visitors.^[9]

Petting zoos are minimally regulated. Guidelines based on the NASPHV compendium were adopted by the North Carolina Department of Agriculture and Consumer Services (NCDACS) after the outbreak. In addition, a law^† was enacted in North Carolina in July 2005 that requires sanctioned agricultural fairs to obtain a permit from NCDACS for all animal exhibitions open to the public. The Arizona Department of Health Services adapted the NASPHV compendium recommendations into educational packets distributed to petting zoo operators statewide.

These recent petting zoo-associated E. coli O157:H7 outbreaks highlight the need to strengthen control measures for such exhibits to reduce disease transmission and prevent similar outbreaks. To reduce human exposure to manure, revised control measures should be considered, particularly those restricting young children from directly entering open-interaction areas of petting zoos.

This report is based, in part, on data contributed by the North Carolina Div of Public Health; North Carolina Dept of Agriculture and Consumer Services; Univ of North Carolina School of Public Health Center for Public Health Preparedness; North Carolina State Laboratory for Public Health; Florida Dept of Health; Florida Dept of Agriculture and Consumer Svcs; US Dept of Agriculture Agricultural Research Svc; and Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, CDC.

Morbidity and Mortality Weekly Report. 2005;54(50):1277-1280. © 2005 Centers for Disease Control and Prevention (CDC)

Cite this: Outbreaks of Escherichia coli O157:H7 Associated with Petting Zoos - North Carolina, Florida, and Arizona, 2004 and 2005 - Medscape - Dec 23, 2005.