Joseph Eid / AFP - Getty Images file

Brightly dyed chicks sold as Easter gifts are part of the problem that sparked an eight-year outbreak of salmonella Montevideo infections that sickened 316 people in 43 states, mostly young children, according to CDC researchers.

It took eight years and multiple tests, trace-backs and interviews with sick owners of fuzzy chicks, but federal health officials say they’ve finally clamped down on an outbreak of salmonella infections traced to live, mail-order poultry.

Between 2004 and 2011, at least 316 people in 43 states were sickened by a strain of salmonella Montevideo that had stumped staff at the Centers for Disease Control and Prevention. An estimated 5,000 additional cases likely went unreported, officials say.

Only through careful analysis of the genetic fingerprint of the bug and cooperation with human and animal health officials and poultry experts did the CDC crew link the cases to “Hatchery C,” a supplier of 4 million birds a year identified only as being in the western U.S.

“It was definitely an interesting outbreak,” said Casey Barton Behravesh, one of a team of CDC researchers who reported on their investigation in the latest issue of the New England Journal of Medicine.

Because the hatchery was cooperative and because the threat of this particular infection appears to be over -- with only one case of the outbreak strain reported so far this year -- CDC officials declined to name the source of live young poultry popular as Easter presents or with urban backyard chicken farmers.

“The problem seems to be under control,” said Behravesh, a veterinarian who is part of the CDC's National Center for Emerging and Zoonotic Infectious Diseases.

But she warned that the larger issue of salmonella sickness sparked by mail-order shipments of chicks, ducklings and other young fowl remains a pressing problem.

“Most people can tell you that chicken meat can have salmonella in it,” she said, “but they can’t tell you that live chickens have salmonella.”

Since 1990, however, there have been 35 outbreaks of salmonella tied to contact with shipments of live, young poultry. CDC officials are investigating two separate outbreaks now, strains of salmonella Altona and salmonella Johannesburg, which together have sickened nearly 100 people in 24 states.

It was the salmonella Montevideo outbreak, though, that sent CDC officials scrambling to find out the source of infections whose victims were mostly children under the age of 5.

80 percent of infections from 'Hatchery C'
In the end, about 80 percent of the illnesses were traced back to Hatchery C, which can ship as many as 250,000 birds a week in the spring, the peak season, according to the report. Even after the hatchery took steps to curtail salmonella transmission, the infections dropped, but did not stop.

Young poultry can become infected with salmonella through contact with birds from different sources, through contact with infected hens or through contaminated feed. Mail-order birds may be stressed by the shipping process, which can make them shed the bacteria.

That demonstrates the difficulty of eliminating salmonella transmission in live poultry, which can swap the bacteria and carry and shed it unnoticed, even though the birds appear healthy, Behravesh said.

Even when state agriculture officials have forced hatcheries to get rid of their birds, clean up the sites and start over, salmonella outbreaks have erupted again.

“Shutting down the hatcheries is not necessarily the answer here,” Behravesh said.

There are some 20 hatcheries in the U.S. that ship an estimated 50 million live poultry by mail-order every year, generating between $50 million and $70 million a year, said CDC officials, citing unpublished data.

In 2011, the U.S. Postal Service shipped some 237,778 boxes or 1.7 million pounds of live poultry, spokeswoman Sue Brennan told msnbc.com.

Many of those birds go to agricultural feed stores, where they may be sold as Easter pets. Others are shipped directly to urban farmers, including many who have adopted the recent trend of raising backyard flocks of chickens.

In this outbreak, the number of illnesses peaked in May of 2006, forcing interventions at Hatchery C, the paper reported.

Those included beefing up biosecurity and rodent control, decontaminating feed, replacing and updating old equipment, changing airflow, improving testing and giving vaccines to adult birds.

Such steps may be recommended, but not required, by the National Poultry Improvement Plan, a program of the U.S. Department of Agriculture. All compliance is voluntary, Behravesh noted.

Still, even after that effort, the salmonella infections didn’t cease completely, Behravesh said.

The CDC researchers called for more targeted efforts to raise awareness about the danger of salmonella infections from live poultry. Only about 21 percent of patients interviewed said they knew that poultry could transmit salmonella and only 7 percent said they were warned about the risk at the time of purchase.

Part of the problem is that people regard the young poultry as pets, often buying chicks dyed neon colors as holiday favors.

“You can make them pink, blue, green or orange,” she said. “They’re very attractive to children.”

Instead, parents and caregivers should realize the poultry is intended as food, not for play, and make sure to practice proper hygiene. Make sure kids wash their hands with soap and running water after every contact with poultry. Take steps to avoid cross-contamination of food and surfaces, such as counters and tables. 

“Do not put the duckling in the bathtub, don’t keep them in the kitchen,” Behravesh advised. 

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