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Understanding PAMTA

The Preservation of Antimicrobials for Medical Treatment Act (PAMTA) was introduced in the U.S. House this spring (H.R. 1549). A companion bill was introduced into the Senate (S. 619). Learn more about them at

The bills call for short-turnaround assessments of antibiotics used for nontherapeutic purposes, defined as “any use of the drug as a feed or water additive for an animal in the absence of any clinical sign of disease in the animal for growth promotion, feed efficiency, weight gain, routine disease prevention, or other routine purpose.”

A critical issue is the unspecified definition of “reasonable certainty of no harm.” Some will interpret that as zero risk, which any reasonable person would recognize as unattainable. The crux is that most antimicrobials used in the beef industry for purposes that would be included in the definition of “nontherapeutic” were approved prior to the requirement of evaluation of antimicrobial resistance potential during the approval process.

These bills set an unreasonable evaluation period in which to work through a large number of approvals. This will essentially result in their removal during the ensuing bureaucratic backlog.

The antibiotics in question in the bills include feed and water uses of any kind of penicillin, tetracycline, macrolide (e.g., tylosin), lincosamide, streptogramin (virginiamycin), aminoglycoside (neomycin), or sulfonamide (sulfamethazine), “or any other drug or derivative of a drug that is used in humans to treat or prevent disease or infection caused by microorganisms.” The ionophores (lasalocid, monensin) and bambermycins (Gainpro) aren't specifically included in the bills at this time.

The Food and Drug Administration's Center for Veterinary Medicine (FDA/CVM) has already done a risk assessment on the use of streptogramins. But it's been left open for further data after failure to determine a risk to human health.

A privately funded risk assessment of the human health risk of macrolide use in food animals has been conducted and published. It found an extremely small risk of human treatment failure as defined by potential resistance in Campylobacter (1 in 10 million) and Enterococcus faecium (1 in 3 billion).

Evaluating product safety is reasonable, but the goal of these bills is to stack the deck so these products won't get a fair assessment (or an assessment at all by the deadline). FDA/CVM needs to work with sponsors to set schedules and provide for the evaluation of the benefits of the drugs.

The really big issue is “routine disease prevention” in animals not displaying clinical signs. This is about the structure of our industry and the ability to prevent illness, suffering and economic losses due to illness and death within this structure.

The risk assessments currently used by FDA/CVM only evaluate the potential risks of antibiotic resistance being passed through the food chain to consumers. They don't evaluate such benefits as healthier animals at slaughter and decreased pathogen loads. These aren't risk/benefit analyses, they're risk analyses.

I'm not a big supporter of using antimicrobials used for treating other diseases as growth promoters. However, when we cross the line to disease prevention, we're talking about impeding our ability to protect animal welfare and conserve livestock resources. Those who blame the need for prevention on our “factory farms” haven't a clue as to all the other things we do to prevent disease.

It appears the bills' sponsors don't envision any adverse effects from inappropriately withdrawing approvals. If we're doing something wrong, I want to know so we can stop it; but for now, I'm contacting my congressmen to let them know that until these bills guarantee a balanced approach with a reasonable timeline, they are wrong for the industry and the U.S.

Mike Apley, DVM, Ph.D., is an associate professor in clinical sciences at Kansas State University in Manhattan.