(Editor’s note: This is Part Two of a recent four-part series by Lynne Terry on how Salmonella in poultry is handled in Denmark and the U.S. The series is being republished by permission from The Oregonian. Part One is here, and Parts Three and Four will be posted over the next two days.)
A sharp spike in chicken-related Salmonella illnesses in Denmark about 25 years ago spurred a food safety revolution that produced what American experts say would not be feasible in the United States: Chicken meat essentially free of Salmonella.
The Danish program required the cooperation of industry, government and researchers, with the country’s top retailer stepping in with an ultimatum, refusing to buy raw chicken meat tainted with Salmonella, which sickens about 200,000 people a year in the U.S.
Processors resisted that ultimatum, saying it would be impossible to meet. But in the end they relented – and succeeded.
Denmark’s road toward Salmonella-free chicken was a long one that had its twists, U-turns and bumps. After illnesses spiked, industry stepped up testing. Flocks were destroyed.
But the results were uneven. In 1996, Denmark adopted a National Salmonella Control Program that established goals, requirements and resources.
Until then, industry had foot the bill. Now a national fund was set up to compensate farmers for slaughtered flocks and losses. The government contributed nearly $30 million and the industry chipped in with about $5 million.
The program was based on a zero-tolerance strategy, requiring that contaminated flocks be destroyed and that tainted eggs and chicken meat be heated to destroy pathogens before entering the food supply.
But that requirement proved to be too stringent. Flocks were so heavily infected that killing them would have led to a shortage of eggs. In 1997, the regulations were relaxed with the focus turned toward eliminating Salmonella from breeder flocks in a top-down approach.
The Danes figured they had to eliminate Salmonella in the first generations of breeders to eliminate Salmonella in meat and eggs consumed by the public.
“If the mother and father are free of Salmonella, the egg is also free of Salmonella,” said Jacob Roland Pedersen, lead veterinarian for Danpo, Denmark’s largest processor.
On the other hand, if the mother is contaminated, she will pass the bacteria on, and, pretty soon, every flock is infected.
“It just spreads like a waterfall,” said Henrik Wegener, provost of Denmark’s Technical University.
To dry up that waterfall, Danish companies told suppliers of breeding stock they would only buy Salmonella-free birds. If birds were positive, the flock was rejected.
At the same time, scientists switched to more sensitive testing. Instead of looking for the bacterium, which is harder to find, they tested for antibodies, which are easier to detect.
“The great thing is that you can actually test the egg yolk for antibodies,” Wegener said.
The new testing was less time-consuming, less expensive and more effective. When Salmonella was present, labs were more likely to find it.
The top-down approach was accompanied by a bottom-up crackdown, too, with the adoption of biosecurity or sanitation measures.
Over time, chicken houses were redesigned to keep Salmonella-carrying pests and rodents at bay. Vegetation was cleared away from buildings and wide gravel paths were installed, encircling structures like a moat.
Houses were designed with three-stage entry halls to prevent farmers from tracking in bacteria. Floors were made from concrete – not clay, which is typical in the U.S. – for easy sanitizing. When flocks were sent to slaughter, after about 36 days, farmers destroyed bedding and washed and disinfected equipment, dedicated clothes and the inside of the chicken house.
Feed was also heated to kill bacteria, and farmers were required to lock up a dedicated feed hose in a sanitary space. They hooked up the hose to the feed truck and attached the other end to the silo to prevent cross-contamination of the feed during delivery.
“This is not rocket science,” said Roland Pedersen. “It’s very, very simple stuff, but it works.”
No vaccines or antibiotics
The Danes decided after talks among industry, government and researchers to ban the use of vaccines, commonly used in hens in the U.S.
The reason, according to Pedersen, is that vaccines reduce bacteria but do not destroy them altogether.
“If you vaccinate, you might not be able to detect if the birds are positive,” he said. “This is not something we can live with.”
Denmark opted to ban antibiotics, which can lead to antibiotic-resistant strains when they are overused, and they prohibited chlorine or other chemical washes during processing, a common practice here.
The Danes refuse to eat chicken treated with chemicals, said Birgitte Helwigh, senior scientist at the National Food Institute.
“I would never buy that,” Helwigh said. “Why should I? It’s not necessary.”© Food Safety News