Published: April 17, 2014
Canadian chicken farmers are putting an end to controversial egg injections, which provided the world with a “textbook” example of the perils of mass medication.
By injecting eggs at hatcheries with ceftiofur, a medically important antibiotic, the farmers triggered the rise of resistant microbes that showed up in both chickens and in Canadians creating a “major” public health concern.
The case – documented by federal and provincial sleuths who track microbes at farms, slaughterhouses and retail meat counters – is held up as powerful evidence of resistant superbugs moving from farm to fork.
“It is going to be in medical textbooks for as long as there are textbooks around,” says John Prescott, a professor with the Ontario Veterinary College at the University of Guelph.
On May 15 injecting eggs with ceftiofur will be banned as part of a new antibiotics policy adopted by the Chicken Farmers of Canada, representing the 2,700 poultry farmers across the country.
“The industry has gone ahead and done this voluntarily, but it is not a voluntary program,” says Steve Leech, the association’s national programs manager. He says the ban is mandatory with penalties and fines for violators.
While the ban is better late than never, Prescott says government should have stopped the injections years ago.
Microbe trackers working with the Public Health Agency of Canada first reported in 2003 that they were picking up higher rates of ceftiofur resistance in Quebec. In 2004, they reported resistance was just as high in Ontario “in both humans and chicken.”
A strain of bacteria called Salmonella Heidelberg, that can cause food poisoning, had armed itself with the biochemical machinery needed to resist ceftiofur. Ceftiofur belongs to a class of antibiotics known as cephalosporins, which are often used on hard-to-cure infections in people.
The scientists soon linked the rise of the resistant Salmonella to chicken hatcheries that were injecting ceftiofur into eggs prophylactically to try prevent infections in chicks.
Quebec hatcheries voluntarily banned use of ceftiofur in early 2005. And over the next two years the rates of resistance dropped dramatically, in both chickens and Quebecers, trends that were closely followed by researchers at the Canadian Integrated Program for Antimicrobial Resistance, or CIPARS.
More than 60 per cent of the Salmonella Heidelberg contaminating chicken was resistant before the ban, but dropped to just 7 per cent in the two years after it went into affect. In humans, 36 per cent of the Salmonella Heidelberg was resistant before the ban, a figure that dropped to 8 per cent.
Then chicken hatcheries in Quebec resumed using ceftiofur and S. Heidelberg resistance began to rise in both chicken and people, prompting the scientists to call for “reductions in ceftiofur use” in a 2007 report.
The organism is “prevalent, invasive and often multi-drug resistant,” they said. And the resistance it carries “can threaten the effectiveness of important human therapies for salmonellosis among other conditions.” Salmonellosis, which causes diarrhea, fever, and abdominal cramps in thousands of Canadians a year, is often caused bacteria picked up by handling raw chicken.
Then in 2010 the team, led by the late Lucie Dutil of the Public Health Agency of Canada, reported in the journal of Emerging Infectious Diseases that the Canadian surveillance showed a “strong correlation” between resistant Salmonella Heidelberg in chicken in retail outlets and the incidence of ceftiofur resistant bacteria causing infections “in humans across Canada.”
The Canadian research is some of the most compelling evidence that antibiotic us in livestock can fuel the spread of resistant organisms in people. It’s been used to support bans on agricultural uses of cephalosporins in Europe, and was held up at hearings in Washington that led to U.S. restrictions on the agricultural use of ceftiofur in 2012.
“It’s really a wonderful study,” says Frank Aarestrup, at the Danish Technical University in Copenhagen, who works with the World Health Organization on antimicrobial resistance.
Like Prescott, he is baffled the findings didn’t trigger more action in Canada.
“It’s really strange,” says Aarestrup. “A lot of the best studies and best scientists are in Canada and nothing is happening on the political side.”
The way Canadian hatcheries were allowed to keep using ceftiofur highlights the “inability” of Canadian health officials to stop inappropriate use of antibiotics, says Prescott.
“There was clear evidence of an adverse effect on public health,” he says, but dealing with the issue fell between the “gaps” in federal and provincial regulations.
“The warning is only a warning, with no regulatory power behind it,”
Ceftiofur was never approved by Health Canada for use in chickens or eggs but hatcheries used it “extra-label,” which falls under provincial jurisdiction.
In response to the CIPARS findings, Health Canada did require that ceftiofur packaging warn of the dangers of “extra-label” use. “The warning is only a warning, with no regulatory power behind it,” says Prescott, who says the government should have stepped in to stop the use of ceftiofur. “It’s what they would do in Denmark, it’s what they would do in Britain.”
“You should be able to do more than make a phone call and say: ‘Cool it guys’,” he said referring way the government opted to work with farmers on voluntarily measures.
Due to lack of monitoring of antibiotics use in Canada, it is not known long hatcheries have been injecting ceftiofur into eggs or how much of the drug was used across the country.
Leech says chicken hatcheries have been reducing ceftiofur use in response the CIPARS findings, and in anticipation of the ban that goes into effect in May.
He says the ban is part of new policy adopted by the chicken farmers to end the “preventative use” of medically important antibiotics, such as cephalosporins and fluoroquinolones, at hatcheries and farms.
Rebecca Irwin, head of CIPARS, says her team is seeing a decrease in resistance in Salmonella Heidelberg nationally. And she says the surveillance network will “be able to track to see how effective that ban is going to be in reducing the potential human burden.”
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