Petting zoo pathogens

The 15 cm of snow that fell last night is as good of an indicator as any that agricultural fair season is over in this region. But, planning ahead is important (and often not done well with fair petting zoos), so it's never to early to make a plan for next season. Petting zoos can be fun and educational, but are also associated with infectious disease risk. There's always some inherent risk with any kind of animal contact, since all animals (and people) carry a multitude of infectious agents. However, understanding pathogen shedding patterns is useful to help determine the best control measures.

A recent study in Comparative Immunology, Microbiology and Infectious Diseases (Roug et al 2012) looked at shedding of selected pathogens by cattle, sheep, goats, pigs, poultry, rabbits and horses at a California county fair. Here are some of the highlights:

  • E. coli O157 was found in one animal. This is the main outbreak concern when it comes to petting zoos, because very low numbers of bacteria are required to cause disease and human infections can be very severe. Surprisingly, the positive animal was a pig, not a ruminant, as would be typical.
  • Salmonella was isolated from feces of 3 animals: 2 pigs and 1 chicken.
  • Campylobacter jejuni, another potential cause of diarrhea in people, was found in 3 animals: 2 cattle and 1 sheep. The 2 positive cattle were adult dairy cattle and they represented 17% of all tested cattle. That's a surprisingly high rate for adult dairy cattle, in my experience.
  • Other Campylobacter species were found in 2 cattle, 3 goats (30% of all goats tested) and 1 chicken.
  • Antibiotic-resistant E. coli were common, particularly in pigs.
  • The parasites Cryptosporidium and Giardia, and the bacterium Vibrio, were not found.

The study didn't look at other aspects of the petting zoo, such as the types of contacts that were allowed, but based on the pictures that were included with the paper, they weren't optimal. Given the results, the picture of two children in the pen with the pigs (including one child who was sitting on the ground leaning against a pig) should raise some concern.

Does this study change anything? Not really, but more information can't hurt. We know that petting zoo animals can carry pathogens, and we have to assume that every animal in a petting zoo is carrying something that could cause an infection given the "right" circumstances. That's why there's a focus on good general hygiene and infection control practices (especially hand hygiene), along with excluding animals that are at particularly high risk. As the authors say "The study findings should not be interpreted as a deterrent to visit agricultural fairs, but as a reminder that good hygiene and sanitation are critical in these settings."

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