As with human medicines, animal antibiotics are carefully monitored by the FDA after they are put on the market. Federal agencies use risk assessments to make decisions about health and safety. These assessments measure and quantify the risks involved in taking or not taking a particular action.
How Risk Assessments Work
In conducting risk assessments, scientists develop a model to describe an issue or potential threat as a series of steps, or chain of events, to assess the next step in the process. By piecing together the chain and measuring the probability of each link, the researcher can calculate the actual risk of an event.
- Does a particular use of an antibiotic on the farm cause a significant increase in antibiotic resistant bacteria?
- If yes, the researcher can then apply available data to assess whether these bacteria species persist further up the food chain.
- If no, the researcher can conclude that the use does not result in a food safety hazard, and therefore is of little risk to human or animal health.
In the realm of animal agriculture, science and risk assessment show that risks from animal antibiotics are minimal. In fact, the potential benefits are more than a thousand times the potential risk. The total disease risks have remained stable or on the decline as antibiotics have continued to be used in animals.
To learn more about how risk assessments work, view this chain of events.
Risk Assessments Results
The FDA, company sponsors and researchers have conducted numerous post-approval risk assessments on animal antibiotics and consistently found very low risk to human health or have shown that not using antibiotics to control diseases might result in an increase in foodborne illness. Research has shown, for example, that:
- The effect of airsacculitis on bird weights, uniformity, fecal contamination, processing errors, and populations of Campylobacter spp. and Escherichia coli. Russell SM., Poultry Science 2003; 82 (8): 1326-1331. In a study conducted at the University of Georgia, carcasses from harvested poultry not treated with antimicrobialsfor a respiratory disease called airsacculitis were more likely to be contaminated by E. coli and Salmonella, thus increasing the risk of foodborne infections.
- Quantifying potential human health impacts of animal antibiotic use: enrofloxacin and macrolides in chickens. Cox LA Jr, Popken DA, Risk Analysis 2006; 26(1): 135-46. A follow-up risk assessment using the University of Georgia data found that not using animal antibiotics can cause far more human illnesses than they would prevent. The estimated human-benefit-to-risk ratio for continued animal antibiotic use on human health exceeds 1000:1 in many cases. The model tested the impact of the use of virginiamycin in poultry as compared to human drug treatment failures. By looking at what would happen over the next five years, the model showed that a ban on the product would result in zero to less than one statistical life saved over the next five years.
- Assessment of the impact on human health of resistant Campylobacter jejuni from flouroquinolone use in beef cattle . Anderson SA, et. al., Food Control 2001; 12(1):13-25. A Georgetown University risk assessment on the use of fluoroquinolones in beef cattle and the resulting human health risk of fluoroquinolone-resistant Campylobacter on beef estimated the risk to humans to be 40 additional hospitalizations and 1 case of mortality over the course of 10 years.
- Public Health Consequences of Macrolide Use in Food Animals: A Deterministic Risk Assessment . Hurd, et. al., Journal of Food Protection, Vol. 67, No. 5, pgs. 980-992. According to the results of an Iowa State University study, the probability of someone in the U.S. experiencing a treatment failure due to the acquisition of resistant food borne bacteria from eating meat from animals treated with macrolide antibiotics (tylosin, tilmicosin) is less than one in 10 million for resistant campylobacter, and less than one in 3 billion for resistant Enterococcus faecium. As one of the scientists said; “People would be more likely to die from a bee sting than for their antibiotic treatment to fail because of macrolide-resistant bacteria in meat or poultry.”
- Assessing Potential Human Health Hazards and Benefits from Subtherapeutic Antibiotics in the United States: Tetracyclines as a Case Study. Cox and Popken, Risk Analysis, 2010. An assessment of the risk of using tetracycline in food animals concluded that reducing tetracycline use in food animals in the United States should not be expected to cause any improvements in human health or to reduce the risks of tetracycline-resistant infections.
- Human health Risk Assessment of Penicillin/Aminopenicillin Resistance in Enterococci Due to Penicillin Use in Food Animals. Cox, et. al., Risk Analysis, Vol. 29, No. 6, 2009. A risk assessment of penicillin used in animal feeds concluded that the use of these drugs were unlikely to seriously impact human health from antibiotic-resistant bacteria.
Additionally, the FDA’s own studies reinforce the results of these and other independently conducted risk assessments. For example, the FDA’s risk assessment on the use of Virginiamycin, a common antibiotic, found that “assuming a food pathway attribution of 10 percent, the average risk to a random member of the U.S. population of having SREF (streptogramin-resistant e. faecium) attributable to animal uses of virginiamycin and that may result in impaired Synercid therapy ranges from 7 chances in 1 billion to 14 chances in 100 million in one year.”
Public policy decisions or actions regarding animal antibiotics should not be made without using risk assessment.
A recent report by the Institute of Food Technologists (Comprehensive Reviews in Food Science and Food Safety, Vol. 5, 2006) made the following recommendation: “Determine the public health impact of antimicrobial resistance on the basis of risk assessment, and consider resistance on the basis of an individual microorganism exposed to a specific agent under a specific condition of use.”
Risk assessments are the proper tools for making public policy decisions about the use of antibiotics in animal agriculture, as they allow policymakers to measure the potential consequences of actions.