Yet scientists already had misgivings. In 1969, the Swann Committee report, commissioned by the British Parliament, concluded the problem of antibiotic resistance was significant. In 1976, a landmark study published in Nature found that resistant E. coli strains could be passed from chickens fed with antibiotics to other chickens, and then to farm workers.
“It was pretty obvious to me that the prudent thing to do would be to take low levels of antibiotics out of animal feed,” said Dr. Hansen, the former state epidemiologist in Kansas. As an F.D.A. employee in 1978, she gathered evidence for Congress linking antibiotic use in livestock to resistant infections in humans, but no action was taken.
“The science was there, the evidence was pretty easy,” she said. “It was a slam dunk.”
The pharmaceutical industry has pushed back. In 1997, researchers from Elanco were among those who authored a lengthy review in the Journal of Applied Microbiology dismissing concerns about antibiotic use in animals, writing, “We are confronted by a lack of information, a wall of ignorance.”
Pharma companies kept a stranglehold on basic information. Various estimates by academics and public policy groups claim as much as 80 percent of American antibiotic sales go to livestock. But the industry has assailed such projections, calling some “agenda-driven junk science,” while simultaneously lobbying to block legislation requiring more disclosure of antibiotic use.
Mr. Simmons of Elanco has long played down livestock’s role in spreading resistant microbes to humans.
“The most serious pathogens are not related to antibiotics used in food animals,” he said. “Of the 18 major antibiotic-resistant threats that the C.D.C. tracks, only two, campylobacter and nontyphoidal salmonella, are associated with animals.”
But such oft-repeated statements, made even in Elanco’s securities filings, refer only to food-borne strains like antibiotic-resistant salmonella that can be found in raw chicken, for example, while ignoring the myriad ways pathogens can be transferred.