Yesterday, the World Health Organization (WHO) released a set of guidelines on antibiotic use in livestock. It suggested outright bans on the use of medically-important antibiotics to reduce resistance worldwide. However, WHO acknowledged that its recommendations are based on “low-quality evidence.”
The four recommendations are:
- Reduce the overall use of medically-important antimicrobials in livestock;
- Ban medically-important antimicrobials in livestock for growth promotion purposes;
- Ban medically-important antimicrobials in livestock for disease prevention purposes; and
- Use medically-important antimicrobials to treat diagnosed illness in livestock only as a last resort.
The guidelines document called the first three “strong recommendations.” However, it said they were based on “low-quality evidence.” The fourth recommendation was called conditional, and said to be based on “very low-quality evidence.”
The guidance justified the recommendations by arguing that the potential benefits to human health “strongly outweigh any potentially harmful or undesirable outcomes.”
WHO, in its announcement of the guidelines, said, “Alternative options to using antibiotics for disease prevention in animals include improving hygiene, better use of vaccination, and changes in animal housing and husbandry practices.”
Rationale and resistance
The WHO guidelines assume the use of medically-important antibiotics in livestock leads to increased resistance that can harm human health.
“Antimicrobial use in food-producing animals can lead to selection and dissemination of antimicrobial-resistant bacteria in food-producing animals, which can then be transmitted to humans via food and other transmission routes,” read the guideline’s executive summary.
However, as the guidelines note repeatedly, the mechanism behind this is not certain.
The guidelines cite international bans on livestock antimicrobial use to theoretically reduce antibiotic resistance. Among these are references to Denmark’s voluntary ban. The American Veterinary Medical Association (AVMA) suggests the Denmark case does not support antibiotic bans in livestock, however.
“When Denmark banned antibiotic use for growth promotion in pork and poultry, animal deaths and disease rose, requiring more therapeutic antibiotic use to treat the resultant diseases. In addition, the Danish ban has not resulted in decreased antimicrobial-resistant human infections in Denmark and has not improved human health.”
The WHO guidelines also cite the Netherlands’ “severe limitations” on the use of antibiotics in livestock, claiming that “no adverse animal health consequences were identified.” However, the AVMA suggests this might have been counterproductive.
“Neither the Netherlands’ nor Denmark’s antimicrobial ban has resulted in decreased antimicrobial resistance in humans. In addition, a study performed in the Netherlands concluded that the therapeutic use of antimicrobials in food animals has nearly doubled in the past decade—one of the likely factors in that increase is the ban on the use of antimicrobials for growth promotion.”
Unsound science claims
The USDA and the North American Meat Institute (NAMI) were quick to counter the guidelines.
“Advocating a blanket ban on using antibiotics to prevent disease is short-sighted and represents a ‘one size fits all’ approach to animal health and welfare,” wrote NAMI in its response to the WHO guidelines.
“Banning using antibiotics to prevent diseases could allow those diseases to take hold in herds and ultimately result in using more antibiotics to treat a disease that could have been prevented.”
Dr. Chavonda Jacobs-Young, USDA Acting Chief Scientist, issued a response only a few hours after the guidelines were released.
“The WHO guidelines are not in alignment with U.S. policy and are not supported by sound science,” he said.
“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.’”
Scope
The WHO guidelines are intended for a global audience, not just the U.S.
“These guidelines apply universally, regardless of region, income, and setting. However, the [guideline development group] acknowledged that implementation of these guidelines in low- and middle-income countries may require specific considerations,” noted the guidelines document. It suggested animal health and hygiene management aid was needed to reduce such countries’ need for antimicrobials.
The U.S. has increased regulations on the use of medically-important antibiotics in livestock, most recently in the form of the veterinary feed directive (VFD). After it was fully implemented in December 2016, the VFD made off-label or production-related uses of medically-important antibiotics illegal. Additionally, producers must obtain a veterinarian prescription to use them to prevent or treat a specifically identified disease.
“While the WHO guidelines acknowledge the role of veterinarians, they would also impose unnecessary and unrealistic constraints on their professional judgement,” noted Jacobs-Young.
The WHO recommendation against any use of medically-important antibiotics in livestock does defer to veterinary judgement “to prevent harm to animal health and welfare,” but it stresses the decision should only be made if that is the only option.
“Veterinarians should not have their hands tied by a blanket ban,” added the NAMI reaction to the guidelines. “Rather, they should be permitted to exercise sound medical judgment in determining what is best for the health of the animal and the health of the herd.”
Elsewhere in the guidelines, WHO recommends that antimicrobials currently not used in livestock should never be introduced to them, saying, “All such uses have the potential to select for antimicrobial resistance, which can be subsequently transferred to humans.”
U.S. data raise questions about the strength of the connection between antibiotic use in livestock and the risk of antibiotic resistant bacteria harming human health suggested in the WHO guidelines.
In its 2013 report—“Antibiotic Resistance Threats in the United States”—the Centers for Disease Control examined many potential areas for resistance to develop. While it did note that antibiotic use in livestock can contribute, it identified healthcare settings such as hospitals and nursing homes as the source of the deadliest antibiotic resistant bacteria. — Kerry Halladay, WLJ editor
