By Melanie Jacob
Journal Editor
[email protected]
With the government proclaiming last week as Animal Health Week, it provides a good opportunity to shine a spotlight on how animal healthcare affects human health.
A recent rising concern amongst Canadians has been how the amount of antimicrobial use on livestock is affecting antimicrobial resistance (AMR) in humans. Antimicrobials, including antibiotics, are used to prevent common and subclinical diseases in livestock. Part of the problem with this is that some of these antimicrobials include growth promotants, which means they're being used for more than just preventative measures.
While there are currently federal regulations in place that address antibiotic and antimicrobial use on livestock farms in Canada, there is no auditing of that use with regards to the quantities used. Moreover, unlike new drugs, older antimicrobials such as tetracycline and penicillin don't require veterinary prescriptions.
To put it simply, the drugs themselves may not have adverse affects on human health, but the overuse of these drugs might be causing AMR in humans.
"The thing that's really questionable at this point is the amount of antimicrobial use in animals that's contributing to resistance in people," said Dr. Betty Althouse, Chief Veterinary Officer for the Ministry of Agriculture for Saskatchewan. "It's really an unknown."
Earlier this year, the Canadian Veterinary Journal published an article documenting recommendations by an ad hoc committee for regulations and tracking of producer drug use on livestock in Canada.
The recommendations by this committee highlighted what level of achievement Canada is at regarding "good stewardship practices." Some key suggestions were "creating a national system to monitor use in food animals," "terminate growth promoters if drugs used in humans," and "stop the importation, sale, and use of antimicrobials not evaluated and registered by Health Canada."
Specific to that latter suggestion is the issue of producers bringing in drugs from across the United States border under the "own use" clause. This clause enables producers to bring over drugs that aren't registered for personal use so long as Health Canada approves them. Nonetheless, the drugs aren't tracked or regulated.
"Health Canada is looking to make changes in regulations and implement a permitting system where producers will have to apply for an import permit that will allow tracking," said Althouse. "They can then figure out what's being brought in and how much."
That's not to say that this clause acts as a loophole. Just because producers are able to bring in and use U.S. drugs in quantities that aren't being recorded doesn't mean they have a get-out clause for unsafe drugs. Being approved by Health Canada means they're still safe for humans, but could potentially be contributing to AMR in humans as a result of the quantities used. The same situation goes for antimicrobials within Canada that are registered.
"The drugs are registered with Health Canada to make sure any drug is safe and legal for what it's being used for," said Althouse. "Part of the process will establish withdrawal times (for the various specified dosages) and ensures no residue is left or it's at a level that's proven safe."
In other words, current regulations around livestock antimicrobials only so far as ensuring they're safe for humans by regulating how they're used on animals. They state how long animals have to remain clean before going to slaughter so as to ensure no leftover "residue" remains in quantities harmful to humans. They don't, however, regulate or track how much or how often any drug is used on livestock throughout its lifespan.
Fortunately, aside from the permitting system the government is looking to develop, Canadian and U.S. drug companies have agreed to phase out growth promotant claims for low-level antibiotic claims in livestock feed.
"People will no longer be able to use antibiotics in feed just for growth promotant," said Althouse. "Canada has also streamlined the process a little so drugs can be accepted with the same documents."
Despite these concerns, there is still no scientific evidence directly linking antimicrobial use to AMR in humans. None of the antimicrobial use actually directly links to AMR any more than regular overuse of human drugs do.
