Urban chickens continue to be in the news, with debate about instituting (or enforcing) bylaws banning or restricting the raising of chickens in backyards running next to articles on how to raise your own backyard flock.
People have various concerns, including:
- Attracting wildlife, including predators such as coyotes
- Infectious diseases
- Animal welfare
But, what is the real risk?
The simple answer is: we don’t know.
We know what the concerns are, but how do those correspond to tangible risks to people? That’s the hard part to answer.
A recent paper in the journal Zoonoses and Public Health (Pohjola et al 2016) doesn’t answer the question, but provides some more information.
In the study, the researchers looked at 51 backyard chicken “farms” in Finland in 2012-2013. Ninety-four percent (94%) of these “farms” had less than 50 birds, so probably similar to the urban chicken situation in North America. Cloacal (rectal) samples were collected from 457 chickens from these farms and tested for Salmonella, Listeria, Yersinia and Campylobacter, bacteria that can cause gastrointestinal disease in people (and animals). They also collected environmental samples from the properties and tested them for the same bugs.
Here are the highlights of their findings:
- Campylobacter was found on 45% of farms.
- Listeria was found on 33% of farms.
- Salmonella and Yersinia were isolated on only 1 farm each. Salmonella was only cultured in the environment, not chickens, on the positive farm. However, Salmonella was detected by PCR (which looks for the bacterium’s DNA instead of trying to grow the bugs) in two chickens.
- Overall, 13% of chickens were positive for Campylobacter.
The (reasonable) conclusion was the backyard flocks represent a potential source of pathogens, particularly Campylobacter.
Does that mean they cause disease?
I’ll get to that next in Part II.