November 28, 2011
British Columbia poultry farmers and veterinarians are being warned by the Public Health Agency of Canada to stop the usage of bovine antibiotic on chickens.
The agency believes the practice is behind a significant spike in a strain of bacteria found in chicken that is resistant to an antibiotic commonly used to treat respiratory infections in human beings and cattle.
Routine testing of chicken from grocery stores detected a dramatic spike in drug-resistant Campylobacter bacteria in retail samples of B.C. chicken in 2009 and levels have remained stubbornly above normal in this province ever since.
Positive tests for the resistant strain of Campylobacter in retail chicken have ranged as high as 40% in B.C. and 28% in Saskatchewan compared with an average of less than 4% in the other provinces monitored by the Canadian Integrated Programme for Antimicrobial Resistance Surveillance.
Campylobacter is the most common food-borne pathogen in Canada. It is usually associated with substandard food handling and consumption of undercooked chicken.
The rate of human Campylobacter poisoning in B.C. has been about 30% above the national average during the past 10 years, according to the BC Centre for Disease Control.
People who contract drug-resistant Campylobacter from contaminated food can become more severely ill with diarrhoea, fever and abdominal pain than those who get typical Campylobacter, the bulletin stated. Thorough cooking kills the bacterium.
A total of 1,750 cases were reported in B.C. during 2009, but it is not known whether any of those cases were antimicrobial-resistant.
CIPARS is comparing Campylobacter from human cases in B.C. and Saskatchewan to the bacteria from retail poultry to determine whether the same pathogen is infecting people who eat poultry.
A bulletin to be released this week by CIPARS attributes the increase in drug-resistant Campylobacter in B.C. chicken to use of the antimicrobial drug fluoroquinolone. The agency says veterinary fluoroquinolones labelled for cattle are being used "off-label" to prevent salmonella in chicken in breeder flocks.
Antibiotics are sometimes used in crowded, large-scale chicken rearing to prevent fast-spreading illnesses from infecting entire flocks.
Health Canada requires fluoroquinolone-based veterinary drugs for cattle to carry a warning not to use them in any other species. Public health authorities want to curb the use of fluoroquinolone in chickens because the risk of spreading drug resistance could render those medications ineffective.
It is not unusual for veterinarians to use antibiotics labelled for one species on another species, but steps are being taken within the poultry industry to stamp out the practice. However, veterinarians are approved to prescribe veterinary and human drugs according to the recommendations of Health Canada or off-label at their discretion, according to John Brocklebank, deputy registrar of the College of Veterinarians of British Columbia.
B.C.'s poultry farming association has issued a warning written by Ministry of Agriculture veterinarian Bill Cox in a July bulletin instructing producers not to use prescription drugs on their flocks except under veterinary supervision and not to use any drug without a veterinary diagnosis.
Chicken Farmers of Canada executive director Mike Dungate said antimicrobial resistance is one of the industry's "critical" concerns. Chicken producers are required to report all medications given to their flocks to the Canadian Food Inspection Agency before they are sent for processing. That information is verified by government veterinarians, according to CFC safety programme manager Steve Leech.
The CFC and CIPARS are developing a national on-farm surveillance programme designed to record antimicrobial use and pinpoint the sources of antimicrobial-resistant pathogens. "The CFC hopes the programme will explain B.C.'s persistently higher incidence of antimicrobial-resistant Campylobacter and correlate that with on-farm practices," Leech said. The CFC maintains there is no conclusive use of veterinary drugs on farms with the drug-resistant bacteria detected in samples taken from chicken in B.C. grocery stores. But drug-resistant pathogens in food are known to pass to humans, according to the Public Health Agency of Canada.
A spike in the incidence of Salmonella Heidelberg found in chicken tested from grocery stores in Quebec in 2003 and 2004 was accompanied by a rise in human cases of the same drug-resistant salmonella in humans.
Although CIPARS doesn't have the authority to collect data about veterinary antibiotic use at the provincial level, researchers learned from industry sources that 70% of hatchery operators in Quebec were using the antibiotic ceftiofur on healthy birds to prevent E. coli infections, according to Rebecca Irwin, director of the surveillance division of the Laboratory for Foodborne and Zoonoses at the Public Health Agency of Canada.
The incidence of the drug-resistant strain subsided in both humans and chickens after Quebec hatchery farmers voluntarily stopped using the antibiotic, she said. "It was pretty good evidence that (human and animal illness) are linked with a very high correlation," she said.
A conference of veterinarians, producers and agriculture regulators held earlier this month in Toronto called on government and the poultry industry to improve surveillance of antimicrobial resistance and close loopholes that allow use of non-approved drugs.