Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2006
Publication Date: 1/1/2007
Citation: Keen, J.E., Durso, L.M., Meehan, T.P. 2007. Isolation of Salmonella enterica and shiga-toxigenic Escherichia coli O157 from feces of animals in public contact areas of United States zoological parks. Applied and Environmental Microbiology. 73(1):362-365.
Interpretive Summary: Zoonotic enteric human disease outbreaks in the U.S. associated with exhibits that permit human-animal contact (e.g., agricultural fairs, petting zoos, or open farms) have increased in the past decade. These outbreaks are usually attributable to Salmonella and especially to Shiga-toxigenic E. coli (STEC) O157 bacterial infections. At least 17 animal exhibit-associated STEC O157 and four Salmonella outbreaks have occurred in the U.S. since 1990. Human-animal contact exhibits are heterogeneous, varying greatly in their hygiene and sanitation practices, the degree of supervision and animal contact permitted, and in facility design. The Association of Zoos and Aquariums (AZA) is a non-profit organization of 211 (in 2005) North American zoos, aquariums, and wildlife centers which attract ~142 million visitors annually. About half of AZA-accredited institutions have human-animal contact areas (e.g., children's zoos). Our goal was to estimate AZA-institutional and individual animal fecal prevalence for both Salmonella and STEC O157. Recent surveys demonstrate that production and fair livestock frequently shed both STEC O157 and Salmonella in their feces in summer. We hypothesized that the more standardized conditions and generally higher hygiene levels achieved in AZA exhibits would result in lower pathogen fecal prevalence compared to animals in production or fair settings. AZA institutions with human-animal contact venues were recruited to participate voluntarily and confidentially. Fecal specimens were collected in summer of 2003 and 2004 from a census of contact exhibit animals and cultured for Salmonella and STEC O157. Thirty-six AZA zoos provided feces from 997 animals, including 526 goats, 192 sheep, 59 horses, 49 cattle, 45 pigs, 33 deer and 93 additional animals. STEC O157 was isolated at one zoo from one bovid. Salmonella was isolated at four zoos from three goats, one horse, one bovine, and one giraffe. Salmonella or STEC O157 was isolated from at least one animal at five of 36 zoos (13.9%). Individual animal fecal prevalence of STEC O157 (1/997 = 0.1%) and Salmonella (6/997 = 0.6%) was very low in AZA zoos both in absolute terms and relative to the high summer prevalence (often >25%) for these same two pathogens in farm production or agricultural fair settings. AZA human-animal contact exhibits appear to present a low zoonotic enteric bacteria risk to human visitors at this time compared to other settings where human-animal contact may occur. Understanding the basis for this low prevalence could benefit pre-harvest food safety efforts aimed at lowering enteric zoonotic bacteria occurrence in farm livestock destined to become food.
Technical Abstract: Fecal prevalence of subclinical Salmonella and Shiga-toxigenic Escherichia coli O157 among animals in human-animal contact exhibits at United States Association of Zoos and Aquariums-accredited institutions was estimated to assess public health risk. Prevalence was less than 0.6% for both zoonotic pathogens among 997 animals sampled at 36 exhibits.