Antibiotics: the danger of them ruling the roost

Antibiotics: the danger of them ruling the roost

I was somewhat startled to read a claim by our chief scientist, Sir Peter Gluckman, that antibiotic use in agriculture in New Zealand is low compared with other countries.

Sir Peter was responding to suggestions that we need to drastically reduce our use of antibiotics in the face of the growing threat of superbugs that are resistant to all antibiotics.

Sir Peter is right that we don't use as many antibiotics in agriculture as some countries, such as America, where 80 per cent of antibiotics are administered to animals, often to make them grow more quickly, rather than to treat disease.

But our use of antibiotics in agriculture can hardly be described as low, when around 65 tonnes of antibiotics are used in agriculture every year - about 60 per cent of the total amount of antibiotics used in New Zealand - and when millions of animals that are not even sick are fed antibiotics continuously for all their lives.

Eighty-five million chickens are reared in factory farms around New Zealand every year, and antibiotics are mixed into their daily feed or water - a practice that inevitably creates a reservoir of bacteria that are resistant to antibiotics, and superbugs that can spread to humans.

The practice of continuously feeding antibiotics to chickens has been going on quietly for decades, and is justified as a way of preventing disease from sweeping through chicken flocks, because on most poultry farms, 20,000-29,000 chickens are crammed together in a shed, where they peck away on their own excrement.

The problem is that feeding low doses of antibiotics continuously to millions of chickens in this way provides an ideal environment for antibiotic resistant bacteria to emerge.

And that's why scientists are warning that this practice is contributing to the rapid rise of superbugs resistant to antibiotics.

If any antibiotic resistant bacteria remains on chicken meat that is not cooked properly, or on cooking utensils, they can make people sick, or pass their resistance onto other bacteria in our intestines, and spread antibiotic resistance that way.

This is a serious concern, given that many of the antibiotics that are used in agriculture are from the same classes of antibiotics that are used in human medicine, such as streptomycin and zinc bacitran.

I had a frozen chicken from a Christchurch supermarket tested several years ago, and five different antibiotic resistant bacteria were detected on its skin.

Chicken meat is not routinely tested for antibiotic resistant bacteria, however, so there's no way for consumers to work out whether chicken is contaminated in this way or not.

Another concern is that antibiotics are poorly absorbed by chickens, so much of it ends up in chicken manure which is often spread around the environment as fertiliser, or ends up in waterways or groundwater.

IT'S not only chickens that are routinely fed antibiotics, either. Pigs and calves are often administered them for parts of their lives. And antibiotic use in the dairy industry is escalating, too, as dairy farmers struggle to keep mastitis at bay.

Dairy New Zealand promotes a programme, called the Smart SAMM plan, in which long-acting antibiotics are injected into cow's teats for around six weeks when they have stopped milking, and the teats are sealed up with a glue, to keep the antibiotic in place.

The industry says it doesn't use milk from cows when antibiotics are being used, so there's no risk of drinking antibiotic residues in milk. But the antibiotics that are injected into millions of cows end up in cow manure, and are spread around the environment, and no doubt leach into waterways as well. Who knows what damage they cause to worms and other microbial life in the soil?

As the world comes to grips with the fact that we are entering a post-antibiotic era, in which new, untreatable bacterial infections are emerging that are resistant to any antibiotic, surely it's time to question the over use of antibiotics in agriculture.

There's little point in a nationwide campaign to reduce the amount of antibiotics we humans use if at the same time we turn a blind eye to the massive use of antibiotics in agriculture.

You can imagine the uproar if it was discovered that some families were feeding children breakfast cereals laced with antibiotics as a way of preventing them from getting infections.

So it's a mystery to me why society is silent about the practice of feeding antibiotics to millions of animals that aren't even sick, as a way of preventing disease.

So instead of downplaying the amount of antibiotics that are used in agriculture, I suggest the chief scientist convenes a panel of experts to explore ways that we can reduce the use of antibiotics in agriculture, and calls for an end to the practice of giving antibiotics to animals that are not sick.


Sue Kedgley