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The FDA is cracking down on antibiotics on farms. Here’s what you should know.

This week, the Food and Drug Administration announced new policies to curtail the widespread use of antibiotics in cows, pigs and chickens raised for food. Critics say the moves didn't go nearly far enough. So why is this such a huge fight, anyway?

The basic problem here is pretty simple — and scary. Antibiotics are utterly indispensable to modern medicine. But they're also starting to lose their effectiveness: Antibiotic-resistant bacteria are spreading fast and now kill at least 23,000 Americans each year.

One reason we're seeing so many new, resilient bacterial strains — from staph to strep to salmonella — is that we're overusing the antibiotics we already have, scientists say. This gives bacteria more opportunities to evolve and essentially outsmart these drugs.

There are a number of culprits. Many doctors still over-prescribe antibiotics for their patients. But large farms are another place to look: By some estimates, nearly 80 percent of all antibiotics in the United States are used on livestock, both to control disease and to promote animal growth. The FDA wants to phase out the use of antibiotics for animal growth over the next three years. It's also proposing greater veterinarian supervision of antibiotics. But critics say there are still plenty of loopholes here.

That's the quick summary. But there are lots of twists and complications. Here's an overview:

Why are antibiotics so important? Where to begin? Ever since the discovery of penicillin in 1928, antibiotics have been used to treat a wide range of bacterial infections, from strep throat to tuberculosis. Before the advent of antibiotics, infections that we now think of as manageable — pneumonia or even simple skin infections — were often death sentences.

If anything, though, this understates just how important antibiotics are to modern medicine. As Mary McKenna explored in a recent Medium story, doctors routinely use antibiotics to reduce the risk of infection from surgeries, kidney dialysis, prosthetic implants and transplants. Without antibiotics, one out of every six people receiving a hip replacement would die. Childbirth would become far more dangerous. We really, really don't want antibiotics to lose their effectiveness.

Are antibiotics losing their effectiveness? This has always been a risk. Bacteria are able to reproduce rapidly — given enough time, they can often work out survival strategies against drugs. The first strain of penicillin-resistant staph appeared way back in 1940.

But the problem seems to be accelerating of late, as antibiotics have gotten cheaper and are used more widely. After two recent antibiotics were introduced — linezolid in 2000 and daptomycin in 2003 — signs of resistance appeared within just a few years:

That's worrying: Already, at least 2 million people in the United States become infected with antibiotic-resistant bacteria each year. At least 23,000 people die as a result. Doctors are starting to report cases where patients have hospital infections that aren't responsive to any treatment whatsoever.

"If we’re not careful, we will soon be in a post-antibiotic era," said Thomas Friedan, director of the Centers for Disease Control and Prevention (CDC), earlier this year. "For some patients and some microbes, we are already there.”

Can't we just make new antibiotics? In theory, yes. But pharmaceutical companies are  increasingly reluctant to sink so much money — between $800 million and $1.7 billion per drug — into antibiotics that can quickly lose their effectiveness. The pipeline for new antibacterial drugs is shrinking:

So how do we stop antibiotic resistance from spreading? Every time we use antibiotics, we increase the odds that resistance will develop. So, the CDC suggests, we should use antibiotics only when they're absolutely necessary to treat infections.

"Up to 50% of all the antibiotics prescribed for people are not needed or are not optimally effective as prescribed," the CDC says. What's more: "Antibiotics are also commonly used in food animals to prevent, control, and treat disease, and to promote the growth of food-producing animals. The use of antibiotics for promoting growth is not necessary, and the practice should be phased out."

Do doctors really over-prescribe antibiotics? It seems so. One recent study in JAMA Internal Medicine found that doctors prescribe antibiotics in 60 percent of all sore throat cases — even though only 10 percent of cases involve strep, the specific condition requiring antibiotics. A separate unpublished study by the same authors found that doctors prescribe antibiotics in 73 percent of cases of bronchitis — even though, they say, evidence suggests the ideal number is closer to zero.

McKenna reports that the health-care industry is starting to take this problem much more seriously: "In the meantime, the medical industry is ... trying new ideas: building automatic scrutiny of prescriptions into computerized medical records, and developing rapid tests to ensure the drugs aren’t prescribed when they are not needed." Warnings about over-prescribing are becoming more common. But the shift has been slow.

Okay, let's get to the farms. Why are so many antibiotics used in farms? Three main reasons. First, antibiotics are often used to treat diseases and infections among animals, just as they are for humans. That's straightforward enough.

Second, antibiotics are often used to prevent the animals from getting sick in the first place. On large industrial farms, for example, livestock are often packed together in tight quarters, making them prone to infection and disease. Small daily doses of antibiotics can boost their immune systems and ensure survival.

Then there's a third, more controversial reason: Ever since the 1950s, livestock farmers have realized that feeding small, frequent doses of antibiotics to cattle, pigs and chickens can help promote growth and improve feed efficiency. (In other words, the animals need to eat less food to reach a given weight.)*

That all adds up: In 2011, 80 percent of all antibiotics sold by weight in the United States were used for meat and poultry production. Some 685 different drugs are now approved by the FDA for use in animal feed.

What's the argument for phasing out antibiotics on farms? Back in 2008, a detailed report from a Pew Charitable Trust commission argued that "non-therapeutic" uses of antibiotics were playing a role in making our antibiotics less effective — although it couldn't pinpoint the exact contribution. Resistant bacteria were also popping up on farms and spreading off-site. Therefore, the report argued, the use of antibiotics to help animals grow should be phased out and eventually banned.

This isn't a new argument. Back in 1977, the FDA first pointed out that the non-therapeutic use of penicillin and tetracycline in livestock could give rise to new super-bugs resistant to antibiotics. But a proposed ban met with fierce opposition from both industry and Congress, and the FDA has trodden lightly in this area ever since.

What's the downside of phasing out "non-therapeutic" antibiotics on farms? It could make meat, dairy, and eggs more expensive, particularly since the animals would require more feed. In October, the Animal Agricultural Alliance, a coalition of food producers, issued a report arguing that modern agricultural practices are necessary to feed millions of people. (The report also made the case that the farm industry was already using drugs judiciously.)

Hard numbers are hard to find here. One National Academies Study study from 1999 estimated that eliminating non-therapeutic antibiotics from animals would raise food prices by about $5 to $10 per person per year in the United States (when translated into today's dollars).

Is that worth the price? A 2009 study from Tufts University estimated that antibiotic-resistant infections add $20 billion to the annual cost of U.S. health care (that's about $60 per person, on average). Curbing antibiotic use on farms would tackle only an unknown fraction of that problem, but those are some rough numbers.

So what's the FDA proposing to do now? Two big things. First, the FDA will ask the manufacturers of animal drugs to voluntarily alter their labels so that farmers would no longer be allowed to use antibiotics simply to help livestock grow. (The two biggest manufacturers, Zoetis and Elanco, have already said they'll comply with this request.)

Second, licensed veterinarians will need to sign off before antibiotics that are commonly used in human medicine can be used on farms. This is a fairly big change: It means farmers and ranchers will now have to get prescriptions before using certain types of drugs for their animals.

“It’s a big shift from the current situation, in which animal producers can go to a local feed store and buy these medicines over the counter and there is no oversight at all,” Michael Taylor, the FDA’s deputy commissioner for foods and veterinary medicine, told the New York Times.

Why do so many people think these rules are too weak? Some critics, like Avinash Kar of the Natural Resources Defense Council, have noted that the new rules for drug makers are still voluntary — and it's hard to see why pharmaceutical companies would willingly give up a major chunk of sales. Presumably they'll find ways around the rules.

One oft-cited loophole stems from the fact that there's a fuzzy line between "non-therapeutic" and "therapeutic" uses of antibiotics. After all, what's the difference between giving animals low daily doses of antibiotics to prevent disease from overcrowding and giving them low daily doses of antibiotics to promote growth? Can't farmers and ranchers just do the former to evade the ban on growth promotion?

The FDA tried to address this, in part, by putting out specific guidelines for when antibiotics could actually be used for disease prevention (the drugs can only be "targeted to animals at risk of developing a specific disease," not handed out far and wide). Still, some public-health experts, such as Dr. Keeve Nachman, a scientist at the Johns Hopkins Center for a Livable Future, argue that the FDA should ban the use of antibiotics for all disease prevention. Otherwise, little will change.

Who's in favor of the FDA's new policies? Many industry groups, from the Animal Health Institute to the National Pork Producers Council, support the FDA’s policies. The AHI in particular argued that drug manufacturers would have little incentive to evade the new rules.

The FDA also explained that it opted for a voluntary approach because it's a quicker and more efficient route. "It avoids legalistic, product-by-product regulatory proceedings that would take years to complete,” the FDA's Taylor explained earlier this week.

Meanwhile, some public health advocates viewed the new policies as a decent first step — if not a full solution. See, for instance, reaction from the American Academy of Pediatrics or the Pew Charitable Trusts.

Are even stricter rules possible? In theory, sure. All sorts of bills and regulations have been proposed over the years to further restrict antibiotics use on animals. So far, however, farm and pharmaceutical companies have been able to fend them off.

For instance: Rep. Louise M. Slaughter (D-N.Y.), a microbiologist, has tried unsuccessfully for 14 years to pass the Preservation of Antibiotics for Medical Treatment Act. Her bill would ask the FDA to review seven classes of antibiotics that are important for medical use in humans. If the agency found that using these antibiotics in animal feed was contributing to increased resistance, it would rescind their approval for farms. So far, however, that bill has never come close to passing.

In October, a report (pdf) from the Johns Hopkins Center for a Livable Future pointed out that improving the conditions in which animals are raised could reduce the need for antibiotics to keep livestock alive until slaughter. The scientists also highlighted earlier recommendations from the Pew Commission for improved tracking of disease and better handling of manure and other farm waste. Both could help curtail the problem of antibiotic-resistance bacteria.

But, the report said, most bills and regulations that would improve matters on these fronts tend to die a quick death in Congress and state legislatures.

Clarification: Added more detail on how antibiotics help animals grow.