Fresh concerns over use of antibiotics in farming

Horse meat is no joke. But at least it is not killing us. More than 25,000 people across Europe die each year because of bacterial infections that are impossible to treat.

As doctors prescribe ever more antibiotics to cure our ills, the bacteria which cause these infections respond by mutating, resisting and multiplying. Antibiotic resistance is a real killer.

We know that the same classes of antibiotics used to treat humans are given – sometimes liberally – to animals. Last month, a report from the Food and Drink Administration in the US revealed that the meat industry accounts for nearly four-fifths of all antibiotics used.

As with humans, antibiotics can be vital to animal health. The painful udder infection in cows, known as mastitis, is caused by bacteria such as Escherichia coli and Staphylococcus aureus. Antibiotics aren’t only prescribed when the cow is showing clinical signs. During her “dry” period, it is routine on most Irish dairy farms to give the cow preventative antibiotics.

Is this always necessary? The mantra of Animal Health Ireland is that prevention is better than cure, and there are other ways than antibiotics to stop bacterial infection.

Disinfecting the cow’s teats after milking can prevent new mastitis infections by 50 per cent, according to Teagasc researcher Dr Finola McCoy. “Farmers need to take an extra few minutes to really clean the teats,” she says, “but time can be pressured as herds get bigger.”

Infecting chickens

Irish farmers are increasingly using preventative techniques. Sales of vaccines have trebled in the last decade. Dr Donal Lynch, a vet who primarily works with cattle, believes that farmers have moved away from a reliance on antibiotics.

“Vaccination has increased,” he says. “We use less antibiotics now because of herd health programmes and better farm management”.

Feeding newborn calves the first milk from their mother is a simple preventative measure that occurs on most Irish farms. This “colostrum” is packed full of anti- bodies that protect the calf against disease.

The danger for humans is not just the overuse of antibiotics with the consequent mutation of bacteria and their resistance to available medication. It is also the threat posed by the crossover from animal to human of infections and the bacteria required to treat them.

Bacteria are not always fussy about where to settle down and multiply; the gut of a human, a pig or a cow will do nicely. And from there they can bounce in their trillions, back and forth from humans to animals, building up resistance along the way.

This isn’t a new story. In the 1970s, broiler chickens began to suffer from lameness due to a bone infection caused by a strain of the bacterium Staphylococcus aureus.

Researchers from the University of Edinburgh discovered that the bacterium, known as ST5, had jumped across the species barrier from humans in Poland, and from there it flew around the world infecting broiler chicken flocks and acquiring a resistance to a range of antibiotics.

A little closer to home is the story of MRSA ST398 (methicillin-resistant Staphylococcus aureus CC398). Scientists first spotted this strain nine years ago in the Netherlands. A sickly child was taken to hospital by her parents, who were pig farmers. When scientists tested the pigs, they found the same strain of Staph. aureus as was identified in the child. “Pig MRSA” was born.

Last year, US scientists discovered that when this strain first jumped from humans to pigs, it acquired resistance “as a result of farm antibiotic exposure”. In the Netherlands, ST398 accounts for just under 40 per cent of human MRSA cases. It can cause fatal infections in humans, including damage to the heart and blood infections.

To the alarm of the UK dairy industry, last year scientists discovered MRSA ST398 in milk. In October, it was discovered that a retired part-time cattle farmer in the west of Ireland had been infected with the same MRSA ST398.

Beef output

Ireland’s Health Protection Surveillance Centre reported that “it is impossible to completely rule out a link between the patient and animal sources” and that if further cases of this strain of MRSA are identified in humans, then screening for admission to hospital will include those who have had contact with livestock.

MRSA ST398 is resistant to an antibiotic called tetracycline. According to an Irish Medicine Board report in 2010, tetracyclines accounted for 36 per cent of all antibiotics sold in Ireland for veterinary use that year.

Is the discovery of MRSA ST398 in British milk a warning for Irish dairy farmers? Irish dairy and beef farms are expanding. The Department of Agriculture’s Food Harvest targets specify an increase in milk output by 50 per cent and beef output by 40 per cent by 2020. Positive stuff, but this will come with its own pressures.

“If we start intensifying our food production, we need to do this in a sustainable way,” says Prof Séamus Fanning, food safety expert in UCD. “We must withdraw our dependence on antibiotics in farming and keep the drugs for other things.”

Dr Mark Holmes, who led the UK team which discovered MRSA ST398 in milk, says the downward price pressures put on farmers by major retailers can increase antibiotic usage.

“If farmers were not screwed into the ground by the supermarkets and allowed to get a fair price for their milk,” he said in 2012, “they would be able to use fewer antibiotics.”

The use of antibiotics on farms is of concern across Europe. Antibiotics as growth promoters – still allowed in the US – has been banned in Europe since 2006. In 2011, the European Commission published a five-year plan to reduce resistance. Half of the proposed actions address the use of antibiotics in agriculture.

Some believe that with the emerging horse meat scandal, the opportunity for Europe in general – and Ireland in particular – to establish a global reputation for high-quality standards in food production, is significant .

“Our best defence is the water that surrounds us,” says Fanning. “If we’re going to preserve our status as a food island, then we need to up our game. We have a unique opportunity to have proper surveillance across all aspects of our food chain, and we should take it.”

In 2011, a new type of MRSA was discovered in two patients in Irish hospitals. This new strain belongs to a genetic lineage that was previously associated only with cows and other animals, but not humans.

That same year, UK scientists identified MRSA in cows with a near-identical profile to that of the Irish human MRSA. It’s clear that new strains of MRSA that can colonise humans are emerging from animal reservoirs in Ireland and Europe.

Public health challenge

So what do we know about the use of antibiotics on Irish farms? “That’s a good question,” says Fanning. “I wish I had an answer for you.”

The worrying fact is that we don’t know much. The Department of Agriculture, Food and the Marine does not collect data on antibiotic usage on Irish farms. Available data from the global market research specialist, GFK Kynetec, shows that antibiotic sales for large animals in Ireland is increasing.

The World Health Organisation wants to ring-fence three classes of antibiotics they rate as “critically important to human medicine’” – cephalosporins, fluoroquinolones and macrolides. Their concern is that worldwide, the use of these antibiotics on farms has increased eightfold in the last decade. In 2010, these classes of antibiotics represented 12 per cent of the total antibiotic use on Irish farms, according to the Irish Medicines Board, a 50 per cent increase on 2009 levels.

According to Dr Marc Sprenger, director of the European Centre for Disease Prevention and Control, antibiotic resistance is “one of the most serious public health challenges we face”. Because we share antibiotics and dangerous bacteria with farm animals, is it time for the Irish authorities to follow the lead of countries such as like Denmark, where this information has been collected for years?

“Increased surveillance of antibiotic use is critical,” says Fanning. “We need to make sure that data from human consumption of antibiotics is available alongside data from antibiotic use on farms in Ireland. These drugs are the most important that we have for protecting us from infections.”

And if we don’t do this? “Then we will will have no drugs available for future generations.”

* Ella McSweeney is a radio and TV broadcaster, and presenter on RTÉ’s Ear to the Ground