Antimicrobial use in livestock under the microscope

Expert says ‘there definitely is a chain’ connecting farms to the rise in antimicrobial resistance

Antimicrobial resistance is like a forest fire — because only you can take steps to prevent it.

Think about resistance every time you use antimicrobials, producers were told during Alberta Pork’s latest telephone town hall.

Leigh Rosengren

Leigh Rosengren
photo: Supplied

“Any single time one of us uses an antimicrobial, we are tipping the scales toward resistance, said Dr. Leigh Rosengren, a veterinarian and consultant with Rosengren Epidemiological Consulting.

“Does that mean that we should never use them? Absolutely not. What we need to do is stop and think of the cost — both the tangible economic cost of the drug and the larger societal cost of resistance to the immediate benefit of your herd in the use.”

By 2050, 10 million people around the world could die each year from antimicrobial-resistant infections. And 18,000 people in Canada are hospitalized each year with an antimicrobial-resistant infection.

“When we use a product in our pigs, we kill off the susceptible bacteria and resistant bacteria are the population that’s left,” Rosengren said on the conference call. “They go on to reproduce and over time, if that exposure continues, the resistant population can emerge within the pigs.”

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Bacteria can acquire genetic material as resistant elements move around in the gut of the pig, she said. Certain bacteria, particularly E. coli or salmonella, pick up those resistant elements and acquire that resistance.

“Every time an antibiotic is used, it increases the chance for resistance, because we’re always putting that pressure on those bacteria to evolve or maintain the resistant genes that they have,” said Rosengren.

The link to farms

Many people acquire antimicrobial-resistant infections in hospital, but there is an increasing number of such infections acquired in communities. And slaughter plants could be a route for such cases. When an animal is slaughtered, some of the millions of bacteria in its gut can contaminate the carcass and people can then acquire a foodborne infection — commonly called food poisoning — if the meat is handled or prepared improperly. If the foodborne infection is resistant, then antibiotics may not work.

“There definitely is a chain connecting agricultural antimicrobial use to the burden of disease in people,” said Rosengren. “It’s difficult to say how often this happens, but there is a chain there. And for that reason, there is a very intense scrutiny on what we are doing in agriculture in terms of antimicrobial use.”

Part of that scrutiny involves the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). It collects and tests bacteria from farms, abattoirs, and retailers for resistance.

“Bacteria found in pork at an abattoir can have up to 70 per cent bacteria resistant to tetracycline. That’s a high number,” said Rosengren.

While tetracycline is an old drug no longer commonly used in human medicine, it’s still concerning that such a high level of resistance has been established. CIPARS has also been tracking resistance to drugs that are of high importance to human medicine.

“In that situation, the pork industry has a good-news story,” said Rosengren. “Less than five per cent of those E. coli are resistant to antimicrobials that are of high importance to human medicine.

“But the take-home message is that it is being watched. We’re in a good situation as an industry now, but we need to continue to work hard to make sure that resistance doesn’t emerge and establish.”

Change is coming

Producers in this country can still use some antimicrobials without a veterinary prescription. But Health Canada and the Veterinary Drugs Directorate are reviewing this and considering whether veterinary oversight should be increased.

“That’s something producers should be aware of,” said Rosengren. “That will probably be changing over the next few years. It’s possible that your veterinarian will be more and more involved in those decisions on your farm.”

By December 2016, antibiotics used in human medicine will no longer be permitted for growth promotion purposes in agriculture, and the label claims for growth promotion will be removed.

“In some instances, you will need to have a sit-down discussion with your veterinarian or your nutritionist to discuss if there are other things you can be doing with your feed to get your performance,” she said. “In other situations, it will be a discussion with your veterinarian to discuss whether those products were in there for other reasons, to control or prevent disease.”

Because most drugs in Canada have label claims for several indications, it’s not anticipated that any products will be removed from the market.

“What will change is how we’re using them, and the veterinary involvement in these decisions,” she said.

Antibiotics of high importance in human medicine, such as Exceed and Baytril, should never be used in an extra label manner. Any producer using those products should be talking to their vet. They should also be discussing their antimicrobial use protocol, she said.

“Most veterinarians are very proactive in taking on samples to test for susceptibility so that they can be picking the most appropriate drug for the situation,” she said.

Producers might also want to participate in CIPARS.

“I think we’re going to see more action towards collecting antimicrobial use data, so we can better understand the relationship and the choices that we make on our farms to the resistance we see.”

About the author

Reporter

Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."

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