New WHO guidelines: Don’t use antibiotics for growth promotion in animals

As global health leaders warn that antibiotic resistance is leading to the end of modern medicine, the World Health Organization (WHO) issued guidelines to prohibit or restrict using antibiotics to feed animals reared for their meat.  Urgent coordinated actions are needed to avoid the end of modern medicine. 

While an effective antibiotic kills most of the targeted germs, a few may survive and develop resistance which can spread to other bacteria that cause the same infection or different infections.  The rate of resistance and its spread can increase if antibiotics are wrongly or over used, and they then become increasingly ineffective to treat bacterial infections.

A key tipping point was reached recently when it was found that some bacteria had evolved to be resistant to colistin, the antibiotic of last resort which is used on a patient when all other antibiotics are found ineffective.

In 2016, researchers in China found colistin-resistant E. coli bacteria in 20 per cent of animals, 15 per cent of raw meat and 1 per cent of hospital patients that were sampled.  The colistin resistance gene (mcr-1) could easily be transferred among different bacteria.

If this resistance continues to spread, colistin will become less and less effective and we will eventually lose the “antibiotic of last resort.”

The colistin story also carries another lesson.  It is widely thought that resistance is due to over-use of antibiotics by consumers or the spread of infections caused by resistant bacteria to patients in hospitals.

However resistance is also spread through the agriculture sector and the food chain, as shown in the study on colistin in China.

In many countries, much of the antibiotics used (80 per cent in the case of the United States) are fed in farms to animals as growth promoters, to make them grow fatter and faster, as well as to prevent or treat diseases.

Resistant bacteria build up in the animals and are present in raw meat.  Some of these bacteria are passed on to humans when they eat the meat.

The environment is another source of the spread of resistance.  Residues and wastes containing resistant bacteria flow from farms and hospitals and contaminate soils, drainage systems, rivers and seas.  Some of these bacteria find their way to humans.

The European Union banned the use of antibiotics as growth promoters in animal feed in January 2006 while the US started action to phase them out in December 2013.

In most developing countries, little action has so far been taken. Hopefully that will start to change.  In November 2017, the World Health Organization issued its first ever guidelines on the use of antibiotics in food-producing animals.

“Scientific evidence demonstrates that overuse of antibiotics in animals can contribute to the emergence of antibiotic resistance,” said WHO’s Food Safety Director, Dr Kazuaki Miyagishima.

A WHO-sponsored study published in The Lancet Planetary Health in November 2017 found that interventions that restrict antibiotic use in food-producing animals reduced antibiotic-resistant bacteria in these animals by up to 39%, according to a WHO press release.

The research paper (authored by William Ghali and 10 other scientists), reviewed thousands of studies, and selected 179 relevant ones, to find if there is an association between interventions that restrict antibiotic use and reduction in the prevalence of antibiotic-resistant bacteria in animals and in humans.

The key findings are that:

• “Overall, reducing antibiotic use decreased prevalence of antibiotic-resistant bacteria in animals by about 15% and multidrug-resistant bacteria by 24-32%.”
• The evidence of effect on human beings was more limited but showed similar results, “with a 24% absolute reduction in the prevalence of antibiotic-resistant bacteria in humans with interventions that reduce antibiotic use in animals.”

This study influenced the development of the WHO’s new  guidelines, which are aimed at influencing policy makers in the agriculture and health sectors.   According to a WHO press release, the guidelines include:

• An overall reduction in the use of all classes of medically important antibiotics in food-producing animals.
• Complete restriction of these antibiotics for growth promotion and for disease prevention without diagnosis.
• Healthy animals should only receive antibiotics to prevent disease if it has been diagnosed in other animals in the same flock or herd or fish population.
• Antibiotics used in animals should be from the WHO list as “least important” to human health and not from “highest priority critically important.”

In 2015, Health Ministers attending the World Health Assembly adopted a Global Plan of Action on anti-microbial resistance, and they agreed that each country should prepare national action plans by 2017.

Since there are many sources of antibiotic resistance, the national effort must include not only the health authorities but also those responsible for agriculture and the environment.

The agriculture authorities should phase out inappropriate use of antibiotics for animals, especially for growth promotion, while the environment authorities should prevent resistant bacteria and genes from contaminating soils, drainage systems, rivers and seas.

By Martin Khor