Exploring the Societal Burden of Animal

Agricultural Antibiotic UseKeeve Nachman, PhD, MHS

Johns Hopkins Center for a Livable Future

Department of Environmental Health Sciences

Johns Hopkins Bloomberg School of Public Health

Background – why are we concerned?• Antibiotics are routinely used in animal agriculture• Therapeutic uses (treatment, control)• Non-therapeutic uses (prevention, growth promotion)

• Same drugs or drug classes as those used in humans• Bacteria in the animal production setting can become resistant• Those bacteria leave the farm and can cause infections in people• Resistant infections are difficult to treat (and expensive!)• Resistance is worsening, and we are running out of treatment options• Our existing approaches to solving the problem aren’t likely to work, and

we have no plans to evaluate them in a meaningful way

Antibiotics administered at

low doses

Susceptible bacteria

eliminated

Resistant bacteria survive

and multiply

Thesis statement• What we know about antibiotic use in animal agriculture suggests it

may be responsible for a significant fraction of resistant infections in humans

Corollary statement:• We lack the data to quantify the externalized societal costs stemming

from misuse of antibiotics in animal agriculture

AMR societal burden estimates• No credible clinical or ag-specific estimates exist!• US • Morbidity and mortality burden estimated by CDC

• 2M infections and 23,000 deaths (20% are assumed to be food-borne)• Underestimate

• Economic burden estimates• Lack of universal/standard accepted methodology for estimation• $20B USD for direct healthcare costs, plus societal/productivity costs of $35B USD• Data are inadequate to differentiate clinical and agricultural contributions

• Global burden• Review on AMR (2016) – 10M deaths and $100 trillion USD

• Very inclusive estimate (includes malaria, TB, HIV, and other bacterial)

Key differences in human vs. animal ABX use

Human VeterinaryDose ranges Therapeutic only Primarily subtherapeutic

Duration Specified, brief Majority of animal lifespan

Oversight Physician-prescribed OTC and veterinarian-prescribed*

Drug selection Often targeted Preventive uses not targeted

Animal use contributes more “selection pressure” – increasing likelihood of killing weaker bacteria and promoting existing (and new) resistant bugs!

What we’d need to know to assign burden• Primary goal – identify fraction of human infections originating from

agricultural misuse

• To do this, we would ideally have:• Antibiotic use pattern information for animals• Molecular characterization of bacteria from food animals and environmental

media around production sites• Molecular characterization of bacteria isolated from humans with infections

• With this information, we would be able to confidently link infections to farms (when a link exists), and match antibiotic uses to patterns of resistance observed in human infections.

But what do we have/what are we already doing?• Antibiotic use pattern information for animals

• Antibiotic sales data from drug manufacturers (ADUFA)• Spotty, low resolution, non-geographic antibiotic use data (NAHMS, ARMS)

• Molecular characterization of bacteria from food animals and environmental media around production sites• Food animals only, to a limited extent, not molecular characterization (NARMS)

• Molecular characterization of bacteria isolated from humans with infections• To a very limited extent, not molecular characterization (NARMS)• Goals of clinical practice do not typically include source determination

Gaps and opportunities for filling them• Moving towards better use data• Agencies have publicly recognized needs for usage data

• Especially in the context of their plan to address misuse• Funding and compliance will be ongoing issues

• Molecular characterization is becoming easier and less expensive• Still not a routine part of clinical practice• Federal programs would need to be expanded to take better advantage of these

techniques• More bugs (not just GI pathogens, but others, too)• Stronger sampling program• Compliance?

Conclusions• We are not able to pin a specific quantitative burden of human AMR

infections on agricultural or human misuse.

• We aren’t collecting the data we’d need to do it, and there are many barriers to doing so – most involving political will

• Do we need to pin down a number definitively before taking more meaningful action than we are?