The Danger Lurking in Factory Farm Chicken

Enlarge Image Image Gallery Poor conditions on factory farms can cause poultry to produce increased levels of a stress hormone that promotes the growth of a dangerous pathogen, Campylobacter, that makes humans sick. PHOTO: ISTOCKPHOTO

For years, as scientists noted what appeared to be a link between increased stress in animals and increased instances of disease, supporters of humane livestock production have suggested a happy animal is a healthier animal. Now a team of researchers from the University of Bristol in the United Kingdom has discovered that high levels of a stress hormone in chickens actually increase the risk of Campylobacter infection.

Campylobacter is a foodborne bacteria that infects an estimated 2.4 million people each year and is one of the top causes of foodborne illness in the United States, according to the Centers for Disease Control and Prevention (CDC). The bacteria can live in the intestinal tract of even healthy birds, passing from bird to bird through common water sources or contact with feces. In humans, Campylobacter infection causes symptoms such as diarrhea, cramping, abdominal pain, nausea, vomiting and fever within two to five days of exposure. The CDC estimates the bacteria kill approximately 124 people nationwide per year.

The British researchers initially surveyed nearly 800 broiler flocks in the United Kingdom and determined risk factors for infection. They found that the health and welfare of the chickens was a significant factor in the proliferation of Campylobacter. “If you compromise the host chicken, its ability to control the infection is also compromised,” says Tom Humphrey, lead researcher for the team who is now a professorial fellow in food safety at the University of Liverpool and science director for the National Centre for Zoonosis Research.

When the researchers isolated the stress hormone norepinephrine and began studying its effects in the laboratory, they found a series of disturbing results. The stress hormone caused rapid growth of Campylobacter and increased its virulence and gut permeability, giving the bacteria an easy way out of the gut and into the chicken meat. “The bacteria’s ability to affect the chicken is enhanced if the bird is in a stressful situation, and the bacteria is also more likely to infect muscle tissues,” Humphrey says.