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Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338

News Release

September 17, 2002

Animal uses of antibiotics affect human health, profs say

Antibiotics for farm animals should be more restricted because they could be affecting human health, according to a committee reporting to Health Canada that included two University of Guelph professors.

Farmers currently have over-the-counter or feed mill access to many antibiotics, which “is contributing to a global pool of resistance,” said committee chair Scott McEwen, a Guelph population medicine professor. “Most food-borne infections that people get are of animal origin, and evidence indicates that most resistance that occurs in these bacteria is from animals.”

The Advisory Committee on Animal Uses on Antimicrobials and Impact on Resistance and Human Health made 38 recommendations for Health Canada to improve the ways it reviews, regulates and monitors antimicrobial use in animals. Antimicrobials is the term that includes antibiotic — a naturally occurring substance that organisms produce to fight off other organisms — and synthetic drugs.

Bacterial resistance to antibiotics can reach people through the food chain or the environment from animals fed antibiotics. Resistance genes can also be passed from animal-source bacteria to bacteria of people. Often a combination of the two processes occurs.

“A central and contentious issue is how much resistance resulting from antimicrobial use in animals finds its way into people, either in the form of resistant bacteria or more indirectly in the form of their resistance genes,” said McEwen. “We know that some bacteria readily exchange genetic information, so if one organism carries genes for resistance, then it may pass them on to another completely different organism to its advantage. The advantage is, of course, that they get to survive antimicrobial drugs, and this is the essence of selection."

All bacteria have the capacity to develop resistance to antibiotics, but some, such as certain types of Salmonella, seem particularly likely to do so. The report cited a Canadian study that found 67 per cent of people infected with Salmonella — which is often transmitted through contaminated food, water or contact with animals — were resistant to one or more antibiotics.

“Antimicrobial drugs are a sacred trust that we’ve not taken seriously enough and have overused,” said committee member and Guelph pathobiology professor John Prescott. “This overuse may have educated bacteria over the last 50 years to become even more expert molecular biologists than they already are.”

McEwen said that many of the panel’s recommendations will have a positive impact on human health while allowing farmers and veterinarians access to the antimicrobials they need to keep animals healthy. If there is more prudent use of antimicrobials in food animals, there should be a reduction in antibiotic resistance, he said. The report recommendations include:

• Making antimicrobials for treatment and control of disease available by prescription only.
• Limiting non-approved use.
• Stopping the importation, sale and use of antimicrobials not evaluated and registered by Health Canada.
• Rapidly phasing out antimicrobials for growth promotion or feed efficiency if they are important in human medicine, are no longer effective in animals or impair the effectiveness of human drugs.
• Designing and implementing an ongoing, permanent national surveillance system for antimicrobial resistance arising from food-animal production.
• Including resistance risks as part of the regulatory review process for new and existing antimicrobials.

The 19 members of the committee from academia, animal welfare organizations, consumer interest groups, the feed industry, the food-animal industry, human medicine, the pharmaceutical industry, public health and veterinary medicine first met in December 1999 and had 10 meetings before releasing the 150-page report.

“It was a challenge to see the way through a mound of complex and sometimes contentious information to produce a document to which we could all put our names,” said Prescott. “This is a well-argued and well-reasoned report that should positively impact Canadians and Canadian agriculture.”

There are three main uses for farm antibiotics or antimicrobials. They are used to treat bacterial infections, to prevent a clinical outbreak of bacterial disease at particular vulnerable stages of the animals’ lives and to promote growth. The growth promoters are the most controversial antimicrobials because they are used primarily for economic reasons rather than to treat sick animals.

In Europe, growth-promoting antimicrobials have been banned. “The committee debated whether it should recommend a ban of all growth promoters, but in the end decided that not all growth promoters select for significant resistence problems, so we reasoned that Health Canada should examine the use of each one carefully,” said McEwen.

There currently aren’t many effective alternatives to farm antibiotics. “Most antimicrobials are relatively cost-effective or farmers wouldn’t use them,” said McEwen. “Veterinarians can help farmers reduce the need for antimicrobial treatment by improving management, making better use of vaccines and improving biosecurity, but we need effective alternatives that are economical and that are also demonstrated to be safe.”

Health Canada has already implemented some of the committee’s recommendations. “They’ve already started surveillance, which is a critical issue,” said McEwen. Although he is optimistic that these changes will lead to a reduction in antibiotic resistance to bacteria, he stressed that they won’t eliminate it. “This is a global problem.”

Added Prescott: “Everyone using antimicrobial drugs — physicians, farmers, veterinarians — has to find ways to use them properly. This report is an important part of the general effort to use antimicrobial drugs more wisely.”

The full report is published on the Health Canada Web site at

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