Bacteria associated with the food supply have long caused human illnesses and deaths. Just a year ago, the U.S. Centers for Disease Control (CDC) issued a warning about the consumption of romaine lettuce from California. People in many states were becoming ill with after eating romaine contaminated with a strain of bacteria Escherichia coli (E. coli); some of those infected required hospitalization. Within the last month, the CDC has linked a new outbreak of E. coli infections caused by the same strain of foodborne E. coli identified last year. Exactly how the leafy greens became a carrier of this illness-causing E. coli was not discovered in 2019, although the use of irrigation water contaminated with animal waste containing the bacteria was identified as a likely possibility. The CDC’s 2020 investigation continues.
Understanding the events that cause outbreaks of bacterial infections in humans and, specifically, the role that animal production plays in the causal chain, has become a critical global challenge. Bacteria are rapidly evolving to resist the medical and veterinary treatments—antibiotics and antimicrobials—that have been developed to control them. Slowing the emergence of such resistance is essential to maintaining human health.
Q1: Don’t antibiotics treat bacterial infections effectively?
A1: Yes, antibiotics (and antibacterials and antimicrobials) are remarkably effectively in treating bacterial infections today. While bacteria are everywhere, only a small proportion of bacteria pose a threat to public health, so diagnosis of the particular disease-causing strains and administration of the right antibiotic are critical. It is important to remember, though, that knowledge of how to combat those strains of bacteria that threaten human health is, in historical terms, relatively recent. The discovery and mass production of antibiotics in the mid-twentieth century revolutionized treatments for several serious diseases. The availability of penicillin permitted effective treatment of pneumonia during the Second World War. Antibiotics, antibacterials, and antimicrobials are now commonly used to speed recovery from a host of bacteria-caused diseases in humans. Antibiotics are also given prophylactically, for example, to prevent possible post-surgical bacterial infections.
In light of such significant human health benefits, the use of mass-produced antibiotics and antimicrobials has grown exponentially in the last 60 years. At times, they have been used inappropriately, for example, to treat sore throats caused by viruses rather than restricting their use to strep throats caused by bacteria. And bacteria have shown remarkable abilities to evolve in ways that enables them to survive and become resistant to the antibiotics administered.
Q2: What do livestock producers have to do with antibiotics?
A2: Livestock producers around the world have recognized the utility of antibiotics and antimicrobials in maintaining the health of their herds, especially of pigs and poultry. A significant share of the antimicrobials administered to food animals are also important in human medicine. In high-income countries, veterinarians often prescribe antibiotics and antimicrobials for food animals therapeutically, that is, when the animals are showing symptoms of illness. But many antimicrobials are used prophylactically, distributed as additives in animal feeds or added by producers to animals’ drinking water. From the 1950s–1970s, such sub-therapeutic use grew rapidly. It was widely believed that prophylactic use of low-dose antibiotics not only prevented infections but also promoted weight gain and generated a real economic benefit. However, scientific evidence now shows that such uses accelerate the development of disease-resistant bacteria that now threaten humans as well as animals. Public health officials in many high-income countries have now banned the practice of prophylactic use of antibiotics in livestock as the risks of antibiotic resistance have been recognized.
In many low- and middle-income countries, however, where veterinary advice is often not available and antibiotics are easily procured over the counter, many smallholder livestock producers purchase what antimicrobials they can find and afford and treat as many animals as they can. The diagnosis and selection of appropriate treatment regime may not be accurate. As commercial feed markets are developed in low- and middle-income countries, the unregulated inclusion of antibiotics in feed could expand prophylactic use of these drugs. However, information on these antibiotic use practices is scarce, and widespread use for food animals is expected to grow. The potential impact on the incidence of bacterial infections on both the animals and the humans who care for them, eat animal source foods, and live in the vicinity of animal production is unknown.
Q3: How important is the link between the common use of antibiotics for both human and animal health?
A3: History confirms that the continued, widespread use of antibiotics or antimicrobials to manage human and animal health will put at risk the capacity to treat new outbreaks of foodborne bacterial infections. Bacterial resistance to penicillin apparently emerged within a decade of its expanded use. Methicillin- and penicillin-resistant Staphylococcus aureus (MRSA) were identified in the early 1960s, signaling the expanding scope of antibiotic resistance. Today, antibiotic or antimicrobial resistance (AMR) poses an increasing threat to public health as the development of new, effective antibiotics and antimicrobials has lagged even as evidence of the risks from current use practices is rising. The fear is that, as AMR grows, the effectiveness of available antibiotics needed to treat serious bacteria-caused illnesses will be diminished, putting millions of human lives and segments of the global food supply important for human nutrition at risk.
Q4: Who is taking action against rising AMR?
A4: Public health authorities and leaders in the food and agricultural sector share responsibilities for addressing the challenges of AMR. Modification of livestock production practices to reduce antibiotic use has become a high priority for many high-income countries, with European countries taking the lead. However, knowledge of the magnitude of AMR among human populations and the potential for modifying the animal husbandry practices that drive AMR in low- and middle-income countries is still limited.
Without adequate data on current use practices and systems of surveillance that communicate timely, relevant information to healthcare providers, food producers, and consumers, it is difficult to raise awareness of and action to reduce the threat of AMR, especially in low- and middle-income countries. Farmers in these countries often lack information about antibiotics and AMR. This information gap is compounded by limited access to vet services that could increase the quality of diagnosis and choice of treatments. And access to the financial resources that would allow livestock producers to manage their animals’ health and production environment appropriately is constrained.
Government entities responsible for human and animal health in all countries often face major challenges in collecting and sharing data that would enable them to do effective surveillance of AMR and to design appropriate interventions. AMR is a multisectoral issue that requires close and unprecedented collaboration among scientists and policymakers.
Q5: Are current efforts to address AMR in line with the potential risks?
A5: Use of antibiotics is often monitored simply with sales figures, a data approach that is less than helpful in devising effective reforms. The more detailed analysis by Van Boeckel et al. of global trends in antimicrobial use in food animals provides a more granular view of the landscape. While the high-income countries that use the greatest volume of antimicrobials for animal production are taking steps to reduce such use, the growth of animal source protein demand in middle-income countries—the result of rising incomes and changing dietary preferences—has led to a steep rise in antimicrobial use. This will result, inevitably, in the emergence of antimicrobial-resistant bacteria that can be transmitted to humans through food, water, personal contact with animals, and environmental contamination. AMR is fast becoming a global health challenge that has highly diverse origins and outcomes in national food systems.
Though there are many specific national programs (in the United States, the NARMS initiative is one such program) to conduct surveillance on the emergence of resistant bacteria, the “One Health” approach aims to guide coordinated action at all levels, from global to local. One Health has been developed in recognition of the fact that humans’ health is closely connected to the health of animals and our shared environment and thus requires a multisectoral, transdisciplinary collaboration across national borders. The emergence and spread of the novel coronavirus in 2019 and 2020 underscored the necessity for such an approach. The threat of zoonotic diseases passing from animals or insects to humans is high. Three out of every four new and emerging human diseases are expected to be zoonotic in origin. Periodic outbreaks of swine flu, avian influenza, Ebola, and Lyme disease provide vivid reminders of this threat. The Covid-19 pandemic has made the framework of One Health more relevant to the world today.
Q6: What more needs to be done to protect human and animal health?
A6: Practitioners of the One Health approach struggle to gain traction as public health and livelihood concerns remain in separate policy silos. Local agricultural policymakers are wary of introducing regulations and surveillance regimes that will cause significant economic harm to producers and reduce the availability of nutrition-important animal source foods. Public health scientists are challenged to engage sooner rather than later in monitoring food production and processing practices for potential contributions to AMR. Financial as well as institutional resources required to do preventive analysis and intervention are limited and mobilized only when dangerous outbreaks of bacterial infections have already occurred. Other public health, food, and agricultural agendas are also pressing and compete strongly for public attention and resources.
Recent consultations at the Center for Strategic and International Studies recommended that sharing data across sectors—human health, animal health, the pharmaceutical industry, food systems, and agriculture—is an essential first step. Several high-income countries, like Denmark, have generated evidence to design interventions that reduce the overuse and misuse of antibiotics in animal production while, at the same time, ensuring that their producers’ livelihoods and animals’ health are not negatively affected. However, implementation of National Action Plans for reducing AMR that many low- and middle-income countries have developed with international support remains a challenge. Insufficient political commitment, limited technical capabilities, and the funding resources necessary to put diagnostic and surveillance systems in place all contribute to slow progress in reducing antimicrobial use. At the local level, engagement of community leaders as well as animal producers (involving both men and women) is critical to increasing awareness and laying the groundwork for more AMR-sensitive food and agriculture practices.
Discussions in the United Nations have promoted the reduction of AMR using the One Health approach (i.e., multisectoral, transdisciplinary, and coordinated). The complexity of the food and health systems, though, makes this a challenge for resource-strapped low- and middle-income countries and for the many smallholder livestock producers, veterinarians, pharmaceutical marketing agents, and public regulatory agencies who need to be engaged.
The ongoing Covid-19 pandemic, however, is demonstrating how a broader commitment to tackling AMR might build on the levels of scientific collaboration and public awareness that have been generated by the spread of the novel coronavirus and the search for effective therapeutics as well as preventative vaccines. Focused discussion on how this experience might guide development of new opportunities to address AMR (and zoonotic diseases more generally) should be part of the upcoming United Nations 2021 Summit on Food Systems as it shapes up in the coming months. The recent launch of the International Center for Antibiotic Resistance Solutions (ICARS) with the support of the Danish government as well as the establishment of the AMR Hub at the CGIAR’s International Livestock Research Institute should help to inform this discussion and active follow-up.