In the chicken industry, the S word you need to worry about: salmonella.

Our latest investigation finds that in the U.S., there’s no mandate to control the bacteria on the farms or in the hatcheries where chickens meant for eating are raised. Federal regulation occurs only at a bird’s final stage of life – the slaughterhouse.

Scroll down for an up-close look at one farm’s process to see at which points salmonella can be introduced and spread.

NOTE: Gunthrop Farms chickens haven’t been linked to any human illnesses from salmonella, but keeping the bacteria in check is an ongoing battle across the country.

Chicks arrive at Gunthorp Farms in northern Indiana when they’re just a day old – but they already may have salmonella. Here in the brooder barn, the birds get a vaccine against the bacteria. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
When they’re a few weeks old, the chickens go to live and eat on the pasture. It looks picturesque, but out in the open is another place where they can get salmonella from wild birds, rodents or each other. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
Inside the Gunthorps’ very small processing plant, chickens await slaughter. Before the birds enter this facility, all steps the Gunthorps have taken to control salmonella are voluntary. But in the plant, federal regulation finally kicks in. This means that certain sanitary standards need to be upheld. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
In the kill room, chickens are shackled together before they’re killed. Salmonella, which lives in the chickens’ gut, can get spread onto the birds’ feet, feathers or skin from their feces. In the U.S., about 25 percent of chicken pieces sold in grocery stores are contaminated. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
Blood drains from a bird that’s been stunned and had its throat cut. As the carcasses go through processing, salmonella may spread from bird to bird.Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
Dead chickens go into the scalder and then the plucker to have their feathers removed. As you can see, the birds are mixed together, making it easy for salmonella to spread. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
When the chickens are gutted, there’s a real danger of contaminating the meat and skin with fecal matter, spreading salmonella. The necks are cut off because the Gunthorps have found that leaving the neck attached increases the risk of contamination. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal
The processed birds end up in a antimicrobial wash, a solution used to kill lingering bacteria left on the chicken – inside and out. Federal testing occurs after this step. To meet the standard, 7.5 percent or less of the poultry examined can test positive for salmonella. Credit: Darren Hauck for Reveal Credit: Darren Hauck for Reveal

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Katharine Mieszkowski

Katharine Mieszkowski is a senior reporter and producer for Reveal. She's also been a senior writer for Salon and Fast Company. Her work has appeared in The New York Times, Rolling Stone, Mother Jones, Slate and on NPR's "All Things Considered."

Her coverage has won national awards, including the Alfred I. duPont-Columbia University Award two years in a row, an Online News Association Award, a Webby Award and a Society of Environmental Journalists Award. Mieszkowski has a bachelor's degree from Yale University. She is based in Reveal's Emeryville, California, office.

Julia B. Chan worked at The Center for Investigative Reporting until June, 2017. Julia B. Chan is a producer and the digital editor for Reveal's national public radio program. She’s the voice of Reveal online and manages the production and curation of digital story assets that are sent to more than 200 stations across the country. Previously, Chan helped The Center for Investigative Reporting launch YouTube’s first investigative news channel, The I Files, and led engagement strategies – online and off – for multimedia projects. She oversaw communications, worked to better connect CIR’s work with a bigger audience and developed creative content and collaborations to garner conversation and impact.

Before joining CIR, Chan worked as a Web editor and reporter at the San Francisco Examiner. She managed the newspaper’s digital strategy and orchestrated its first foray into social media and online engagement. A rare San Francisco native, she studied broadcasting at San Francisco State University, focusing on audio production and recording. Chan is based in Reveal's Emeryville, California, office.