Last week the Union of Concerned Scientists published a report on the use of antibiotics in animal feed. Using available sources and some clever reasoning, scientists at the UCS found that American livestock producers use almost 25 million pounds of antibiotics a year for nontherapeutic purposes, mostly to help the animals grow bigger faster. That’s 40 percent more than the industry says it uses. What’s disturbing about this report is that it was new enough to make the headlines.
In two decades you might think that scientists would have gathered plenty of data to buttress their central claim: that the profligate use of antibiotics in animal feed is a public-health crisis in the making. But the drug companies in the United States and most other developed nations have been unwilling to release even basic information on animal-husbandry practices, such as the volume of antibiotics fed to cattle, pigs and chickens. They say that they fear revealing trade secrets, but I suspect the real reason is fear of how the public, already skittish about mad-cow disease, will react. For every ounce of antibiotics an American doctor prescribes for a patient, livestock producers feed more than eight ounces to animals.
At this point it’s worth emphasizing a crucial distinction. The UCS figures do not include antibiotics given to animals that are sick. They include only those given to healthy animals, primarily to promote growth. Back in the 1950s the livestock industry, searching for cheap alternatives to grains, began putting waste from the pharmaceutical industry into animal feed. When they used byproducts from antibiotics production, their animals grew bigger. They didn’t know why, but it seemed like a good thing, so the practice caught on.
America is not the only culprit. Europe feeds as much antibiotics to its animals as it does to its people, according to estimates. Virtually no data are available on the situation in Asia, Africa and Latin America. The World Health Organization’s most recent figures about China date back to the 1970s. At that time China’s livestock industry was on a par with the United States’ in antibiotics use, and there’s every reason to believe they’ve at least kept pace. We know things are bad, because when tourists from Europe and America travel to the developing world, they often bring back ordinary diseases with extraordinary resistance. When we see a resistant strain of salmonella, there’s a 95 percent chance the patient caught it on vacation in Southeast Asia, Africa or southern Europe. In America the Centers for Disease Control and Prevention have shown that salmonella resistance is associated with travel to Mexico and other vacation spots. Globally, antibiotics use is enormous.
As a Danish scientist, I find the UCS report disturbing but not surprising. In Denmark, unlike the United States, regulations require the industry to keep close tabs on its use of the drugs, and veterinarians must write a prescription before antibiotics can be given to animals. Even so, a few years ago our livestock consumed five times more antibiotics than Danes did. When the European Union followed the WHO’s 1997 guidelines for the use of growth-promoting antibiotics, banning the use of drugs given to people, Danish animal producers tried an experiment. They completely stopped using antibiotics for growth promotion. Some experts predicted massive outbreaks of necrotic enteritis, a stomach bug, but this didn’t happen.
What did happen surprised us all: removing antibiotics had virtually no effect whatsoever on animal health and productivity. The chickens and pigs (we have few cattle) grew just as fat nearly as quickly. Feed efficiency declined slightly in chickens–they had to eat more to achieve a given weight–but not enough to raise the price in the stores. With pigs, things are a bit more complicated. Because farmers wean them early to free their mothers to breed, piglets start out in life with weak immune systems. Without antibiotics, about 10 percent of them suffer from diarrhea.
But we no longer live in the 1950s. Livestock production methods have improved, and scientists know much more about diseases and how to control them. In recent years, for instance, we’ve learned which bacteria, Lawsonia intracellularis, causes diarrhea in piglets. We can diagnosis it and cure it by applying antibiotics in a targeted and judicious way that minimizes the bug’s chance of developing resistance. Personally, I feel much better about having a vet treat a disease in 10 percent of a herd than about giving every animal antibiotics until the day it dies. And for what? To prevent a minor problem in a very small period of the production cycle.
In the broad picture, two things are clear. First, humans and animals constitute overlapping reservoirs of resistance. When we use drugs in animals, we are planting the seeds of resistance for people. Second, the development of new antibiotics is so slow that you can hardly call it development anymore. Scientists haven’t discovered any truly new antibiotics since the 1960s but, rather, have merely re-engineered the old ones. To bacteria, resisting these so-called new drugs is a piece of cake. We’ve been living with the idea that we can keep ahead of the bugs, but we can’t. The only solution is to eliminate the misuse and overuse of antibiotics.
