Reckless farm meds feed superbugs
The world was once a place where a bad cut to your hand meant infection and the possibility of death, and surgical procedures that are now routine were life-threatening.
Poverty and poor healthcare infrastructure means this is still a reality in many parts of the world.
But even the future of wealthy countries could look a lot like the past. Medical experts and economists are warning that the rise of antimicrobial resistance (AMR), particularly to antibiotic drugs, could see as many as 10-million people die each year by 2050 and wipe out a cumulative $100-trillion in economic output.
These were the findings of a review on AMR, chaired by economist Jim O’Neill, famous for coining the term Bric with reference to the emerging economies of Brazil, Russia, India and China.
One of the key issues highlighted by the review was the unnecessary use of antibiotics in agriculture, which is unmonitored in many countries. The drugs used to treat animals and also to promote their growth are often important for human health.
In the United States, about 70% of antibiotics classed as medically important to humans are sold for use in animals, according to the review.
The inappropriate use of antibiotics is dangerous for both human and animal health because it is one of the factors driving AMR. It also has serious implications for food security and farmers’ economic wellbeing.
The estimates of global antibiotic consumption in agriculture vary considerably because of poor surveillance and data collection in many countries.
Figures range from 63 000 tonnes each year to more than 240 000 tonnes. But the review notes it is clear that use is widespread, on a scale “at least equivalent to humans”, and will rise.
The review cited estimates that the use of antibiotics in agriculture will rise by 67% between 2010 and 2030, and, in the Brics countries (including South Africa), it will increase by 99%.
The use of antibiotics to promote growth is a particular concern, with the report recommending the introduction of targets that will allow countries to decide how they can best reduce unnecessary use in farming.
In South Africa, there is little data available on the extent of antibiotic use in the production of pork, beef and poultry. Medical and veterinary experts believe that South Africa’s use reflects global trends.
According to Professor Moritz van Vuuren, a veterinary microbiologist in the faculty of veterinary sciences at the University of Pretoria, antibiotics are used for treating disease, preventing its spread and for growth promotion, with about 80% of antibiotics sold mixed into animal feed and water. About 20% are administered topically or by injection.
Of the 80% antibiotics mixed into feed and water, it is not clear how much is used for growth promotion.
“That kind of surveillance needs to be done in the future,” said Van Vuuren, “but you can take it for granted that a sizeable proportion is used for growth promotion.”
Antibiotics should only be used to treat sick animals and, where appropriate, to prevent the spread of disease, he said. But the prophylactic use of antibiotics – giving healthy animals drugs to prevent them getting sick – must be avoided.
Globally, there is a move away from the use of drugs to promote growth, a trend South Africa is likely to follow.
The difficulty of monitoring the extent of antibiotic use in agricultural comes down to cost; surveillance programmes are expensive and require a partnership between the government and other role players, he said.
The laws that govern how antibiotics are dispensed to farmers also play a role in how they are used. Two Acts govern veterinary medicines – the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act of 1947 and the Medicines Control Act of 1965.
Under the stock remedies Act, farmers can buy some antibiotics over the counter to use as they see fit and without the guidance of a veterinarian. The intention of the Act was to enable farmers in rural areas, with little or no veterinary services, to get access to medicines.
Over time, the list of over-the-counter antibiotics has expanded and includes a major group of antibiotics that can be used to promote growth, Van Vuuren said.
There is much debate in the sector about changing this, but South Africa is a developing country and many farmers still don’t have veterinary services, he said.
There is a tension between access and excess, which is pertinent for a country that has roughly 35 000 commercial farmers, between two and three million small-scale farmers, and eight- to 10-million subsistence farmers, Van Vuuren said.
The Medicines Control Act covers scheduled antibiotics, and only veterinarians can prescribe and dispense them.
Some more modern antibiotics are not registered for use in animals, Van Vuuren said.
Antibiotic use selects out resistant bacteria in animals, just as it does in humans, said Professor Marc Mendelson, co-chairperson of the South African Antibiotic Stewardship Programme.
“The more antibiotics are used, the more resistant strains are selected out and therefore can be transferred to humans during the journey from production to plate,” he said. Antibiotic residues end up in meat, and antibiotic residues and antibiotic-resistant bacteria enter the environment.
But the rise of AMR cannot be attributed to the use of antibiotics in agriculture alone.
The misuse of these drugs in human medicine is also a major contributor to resistance. It requires a global awareness campaign about antibiotic misuse and overuse in human and animal health, and in all other walks of life that introduce resistant bacteria into the environment, Mendelson said.
One of the few surveillance programmes of AMR in South Africa is provided by V-Tech, a veterinary pharmaceutical firm. The programme began in 2006 and covers poultry farms, cattle feedlots and piggeries countrywide, according to V-Tech’s chief executive and veterinarian, Johan Oosthuyse.
Earlier this year, the programme identified increasing cases of Colistin-resistant bacteria in poultry farms.
The early generation antibiotic, once not recommended for use in humans, has become a drug of “last resort”, because organisms have adapted to newer classes of antibiotics, leading to the rise of so-called superbugs.
Mendelson explained that a new mechanism to transfer a Colistin-resistant gene known as MCR-1 has been identified in bacteria, first in feed animals in China and later in other countries, including South Africa.
There is also a concern that this gene can now be transferred between different types of bacteria that cause more serious diseases in animals, and, according to Oostehuyse, potentially humans.
The cost and implication of reducing reliance on antibiotics in agriculture needs further exploration. The O’Neill review acknowledged the significant gaps in data for both surveillance of antibiotic use in agriculture and the economic costs.
It did note that a 2015 study by the US department of agriculture showed that producers that use antibiotics for production rather than treatment would suffer a decline of less than 1% in the value of what they produced.
The ability of the local agricultural sector to reduce its reliance on antibiotics can be done with better biosecurity or actions that safeguard the health of farm animals, Van Vuuren said. These include vaccinations, optimal nutrition for animals and access control on farms.
But the total elimination of antibiotics in agriculture is unrealistic, Oosthuyse said. South Africa has a “high animal disease challenge”, which is aggravated by informal farming.
The department of agriculture, forestry and fisheries did not respond to requests for comment.
Poultry industry wants responsible use of antibiotics
Chicken is a much-loved source of protein for South Africans. Antibiotics are commonly used both for preventing and treating disease and to improve growth, according to Dr Charlotte Nkuna, senior executive at the South African Poultry Association.
Growth promoters are simply a class of antimicrobials, not used in human medicine, to help manage the gut health of poultry. Better growth results because birds with healthier guts are able to use their food more effectively.
The organisation discourages the routine use of antimicrobials for prophylactic purposes unless a diagnosed disease is being managed, she said.
Farmers should monitor the effectiveness of the drugs used and avoid using the last-resort antimicrobials, unless the use of other drugs will prolong the disease.
Although Colistin was not used in poultry for many years, its use has increased after it was found to be more effective in treating some conditions.
Resistance is not unique to Colistin, Nkuna added, but the drug is used for the treatment of human conditions, which makes it a more serious issue.
The emphasis should not be on the reduction of antibiotic use in agriculture but on “responsible use”, she said.
Vaccines were alternatives for some diseases and there are alternatives for promoting gut health such as organic acids. Neutriciticals – herbal or natural products – are also being researched to assist in managing respiratory and gut health, Nkuna said. – Lynley Donnelly