Last week, the World Health Organization released new guidelines that recommend livestock producers halt routine antibiotic use in order to combat the urgent public-health problem of antibiotic-resistant bacteria. Specifically, WHO calls for an overall reduction in livestock producers’ use of all classes of antibiotics important for human health. This includes an end to antibiotics for growth promotion, and for disease prevention when there is no diagnosis of disease susceptible to antibiotics elsewhere in the herd or flock. When animals are sick, WHO recommends they be tested to determine which antibiotics their illness responds to, and then treated with the option that WHO has classified as least important for human health.
These guidelines don’t have any enforcement authority behind them, but they could prompt countries to adopt or strengthen policies aimed at reducing the use of antibiotics in food-producing animals. STAT’s Helen Branswell writes:
But Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics and Policy, said the recommendations will help health ministries around the world make the case for banning growth promotion to agricultural ministries, which generally wield more power.
“I think the Ag ministry, left to itself, would certainly do nothing. Even pushed by the health ministry may do nothing. But pushed by the health ministry with a WHO recommendation — if nothing else, it stiffens the spine of health ministries in asking for this,” Laxminarayan told STAT.
CIDRAP’s Chris Dall notes that the news conference to release the guidelines included information about the successes some other countries have had in restricting the use of antibiotics in food animals: Denmark, for instance, has seen use of animal antibiotics drop 49% since 1994, while enjoying a 15% increase in meat production.
In the U.S., growing concern about human infections with bacteria resistant to an ever-longer list of antibiotics led to FDA guidance aimed at halting the use of antimicrobials for growth promotion in food animals. Meanwhile, consumer demand for meat raised without the routine use of antibiotics strengthened. Big Chicken author Maryn McKenna explained to Fresh Air’s Terry Gross that it was in response to consumer demand that major US chicken producer Perdue Farms began a process of phasing about antibiotics in 2007 and is essentially antibiotic-free now. And, McKenna reported, major chicken producer Tyson followed suit, and fast-food and fast-casual chains (Chick-fil-A, Subway, McDonald’s) now serve chicken raised without antibiotics. The transition will take longer for beef and pork, but US chicken producers have shown that it’s possible to transition away from routine antibiotic use and still meet this country’s large appetite.
Problematic response from USDA
Consumers and forward-thinking food producers in this country might be heading towards better antibiotic stewardship, but the Trump administration is not on board. USDA quickly issued a news release responding to the WHO guidelines:
Dr. Chavonda Jacobs-Young, USDA Acting Chief Scientist, today issued the following statement:
“The WHO guidelines are not in alignment with U.S. policy and are not supported by sound science. The recommendations erroneously conflate disease prevention with growth promotion in animals.”
“The WHO previously requested that the standards for on-farm antibiotic use in animals be updated through a transparent, consensus, science-based process of CODEX. However, before the first meeting of the CODEX was held, the WHO released these guidelines, which according to language in the guidelines are based on ‘low-quality evidence,’ and in some cases, ‘very low-quality evidence.'”
Claiming that the WHO guidelines are “not based on sound science” suggests a misreading of the WHO publication in question and a failure to appropriately weigh the strength of evidence against the public-health threats.
The full WHO guidelines document explains that the Guideline Development Group used the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to assess the quality of the studies. The authors explain, “The GRADE approach defines the quality of the evidence as the extent to which there is confidence that an estimate of effect or association reported in the available evidence is correct.” Under this system, randomized controlled trials are initially considered high-quality evidence and observational studies low-quality evidence, and then the group considers other factors that can raise or lower the study’s ranking.
A “low-quality” GRADE ranking doesn’t mean a study is shoddy and should be disregarded; it means that confidence in its precision is low. A single study with a low GRADE ranking probably shouldn’t form the basis for major policy changes, but a lot of studies with that ranking whose findings all point in the same direction count as useful evidence. What recommendations a group then makes based on that evidence depend in large part on the severity of the threat and the potential harms of the proposed solution. The WHO guideline report addresses this specifically. Here’s what the authors write about their first recommendation (“We recommend an overall reduction in use of all classes of medically important antimicrobials in food-producing animals”), a strong recommendation with low-quality evidence:
The GDG determined that this recommendation should be strong, despite the low quality evidence, because the beneficial human health benefits (lowered prevalence of antimicrobial resistance in bacteria isolated from humans) strongly outweigh any potentially harmful or undesirable outcomes.
The evidence from the systematic reviews and narrative literature reviews reveals that restricting use of antimicrobials in food-producing animals reduces the prevalence of antimicrobial resistance in bacteria isolated from food-producing animals that are, and can be, transmitted to humans. Extensive research into mechanisms of antimicrobial resistance, including the important role of horizontal gene transfer of antimicrobial resistance determinants, supports the conclusion that using antimicrobials in food-producing animals selects for antimicrobial resistance in bacteria isolated from food-producing animals, which then spread among food-producing animals, into their environment, and to humans. Furthermore, the systematic reviews concluded that broad restrictions covering all antimicrobial classes appear to be more effective in reducing antimicrobial resistance compared to narrow restrictions of one antimicrobial class or drug, even though there are examples of marked reductions in antimicrobial resistance following restriction of a single antimicrobial.
There is enough evidence to act on this serious threat to global public health. USDA might have reasons for not wanting to adopt all of WHO’s recommended policies immediately, but they are wrong to claim the science is unsound.