Agriculture is making an admirable effort towards fighting superbugs but academics see risk elsewhere
Levels of agricultural antibiotic usage have dropped significantly in the past year as the primary industries wrestle with the risk of developing superbugs.
However, academics warn that farmyard use isn’t a big risk in New Zealand and the proverbial genie of antibiotic resistance can’t be put back in the bottle.
According to figures released by the Ministry for Primary Industry’s Food Safety division, New Zealand cut its sale of antibiotics for plants and animals by 23 percent in just one year.
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Antimicrobial resistance is one of the World Health Organisation’s top 10 threats to humanity, with agriculture using an estimated 70 percent of the world’s antimicrobials.
The Ministry of Health, New Zealand Food Safety and representatives from across the human health, animal health and agriculture sectors formed the Antimicrobial Resistance Action Plan in 2017.
The plan aims to manage the risk of creating antibiotic-resistant superbugs by treating antimicrobials as a valuable shared resource so they can continue to treat humans, plant and animals with less of bacterial immunity developing.
Antibiotic sales have been trending downwards since at least 2017, when New Zealand sold a total of 71,361kg of antibiotics for animal and plant usage.
That figure dropped by almost a quarter between 2021 and 2022, when 53,422kg and 41,033kg were sold respectively.
More than half of all antibiotics sold were for use in dairy cattle, followed by 16 percent for pigs, 9 percent for horses and 4 percent for beef cattle, meat poultry, sheep and companion and non-production animals.
New Zealand Food Safety deputy director-general Vincent Arbuckle said the 23 percent drop was good news. “With antimicrobial resistance increasing around the world, and few new antibiotics being developed, careful use of the antibiotics we have will help to keep them effective."
The New Zealand Veterinary Association wants to end routine use of antibiotics to maintain animal health by 2030, and Dennis Scott, from the association’s antimicrobial resistance group, said the country was on track to hit that goal.
“We're never going to have zero antibiotics, because we're still going to have disease, so it's going to be impossible to have zero antibiotic use, but there’s a goal to reduce. Yes, yes, we can. And yes, we are.”
Even though New Zealand’s agricultural antibiotic usage was trending upwards when the association made that commitment, Scott said New Zealand had a very low base level of antibiotic usage for the start, so managing to achieve a reduction of 23 percent in one year was massive.
He said moving away from whole herd treatment with antibiotics to diagnosing and treating individual animals, as well as teat sealing technology for dairy cows had driven the progress.
Critically important
Though major gains have been made overall, the sales of the five critically important antibiotics have shifted less.
Sales of these critical antibiotics, which include penicillin, dropped from 6848kg in 2021 to 6285kg in 2022, an eight percent drop.
The drop from 2017 is more pronounced, with New Zealand logging antibiotic sales of 8952kg.
Scott said these were used more sparingly and only when needed, so major reductions in their use was more difficult and could compromise animal welfare.
Auckland University associate professor of infectious disease Mark Thomas heaped praise on the Veterinary Association and others involved in bringing down the level of antibiotic use in agriculture considering the globally low level of use in New Zealand.
“They are to be congratulated, but humans and antibiotic prescribing for people is not such a great story.”
Thomas said New Zealand was a high user of antibiotics for humans compared with other countries, and though it may be coming down a bit, it wasn’t seeing anything like agriculture’s reductions.
“We still have a very high antibiotic use in humans, and most of the antibiotic resistance in germs that cause disease in humans in New Zealand, are the result of antibiotic use in humans.
“Lots of doctors and other people say, ‘Oh, look [at agriculture], that's where the problem is’. No, it's not. That's rubbish,” Thomas said.
Can’t be undone
Canterbury University professor of genetics and molecular biology Jack Heinemann said the reduction was good news, but there was no level of antibiotic resistance that was desirable, and what had been done already couldn’t be undone.
“There's no evidence at all that using fewer antibiotics will drop back our levels of resistance,” Heinemann said. “It's like a ratchet –once it locks in, it doesn't back off.
“Using less isn't a bad thing, but it isn't the solution either. We have to look at the environment holistically, to understand how to restore susceptibility, not just have a tolerable amount of resistance.”
He said this would just create a “hypercycle of innovation and neutralisation”.
Heinemann said antibiotics had to be thought of as a non-renewable resource, and simply developing and using new antibiotics was just robbing future generations of the value of the drug.
He said this would just create a “hypercycle of innovation and neutralisation” leaving humanity with few options to achieve the same ends.
“We have poor healthcare outcomes [from resistant bacteria already) and they're more expensive. We have less agricultural productivity and it's more expensive. That's only going to get worse.
“That's even if you did subscribe to the philosophy of discovering new drugs. There's no evidence at all that we can discover drugs that are as wonderful as the drugs we've already discovered.”
