American health advocates have filed a lawsuit against the US food regulatory agency to stop a practice they believe is contributing to the rise of antibiotic-resistant infections worldwide. Many large-scale livestock producers around the world feed small amounts of antibiotics to healthy animals to help them grow better. But public health experts say constant exposure is encouraging bacteria to develop resistance to the drugs, undermining their effectiveness in treating human disease. The new lawsuit is the latest round in the long-running battle over antibiotic use in livestock.

Routine practice

Farmers started adding small doses of antibiotics to their livestock feed around 50 years ago, after scientists discovered the drugs improved the animals' growth. The practice became routine, and it is now commonplace in large livestock operations in many countries. Controversy over the practice arose soon after it began as public health experts observed antibiotic-resistant bacteria growing in these animals.

The US Food and Drug Administration first proposed a ban on this use of antibiotics in 1977, but Congress ordered more research.

Steve Roach, with the advocacy group Food Animal Concerns Trust, says evidence has been mounting since then, but the FDA still has not acted. "After 30 years, I think it's time for someone to put a little more pressure on them. And that's what the aim of the lawsuit is."

Roach's group and four other major environmental and consumer groups are suing the FDA to ban the use of two common antibiotics at levels below what is used to treat a sick animal. FDA officials declined to comment on the pending litigation.

Last June, the agency did recommend that livestock producers phase out the use of antibiotics to promote growth. But Roach notes it was just that: a recommendation. "As far as we can tell, all they were trying to do was kindly ask the industry to make changes. And we just don't believe that's adequate response."

Inconclusive evidence?

But the livestock industry says the evidence linking resistant human infections to the farm is not conclusive. And proponents of low-level antibiotic use note that besides promoting growth, the drugs have a therapeutic effect that helps suppress diseases once common in large, confined populations of food animals.

Ron Phillips with the Animal Health Institute, an animal-drug trade association, says that means a safer food supply. "Sicker animals result in greater contamination on the meat. So, the way to control pathogens on the farm so that they don't transfer through the food chain is to make sure we have healthy farm animals."

Antibiotic use in healthy farm animals is not the only source of resistant bacteria. Experts say the largest contributor is antibiotic misuse among people.

But consumers are growing concerned about the effects these drugs might be having on the food they eat. The European Union has banned the use of antibiotics as growth promoters. New Zealand and South Korea have restricted the use of antibiotics in livestock as well, and other countries are considering similar moves.

Some analysts believe that regardless of the lawsuit's outcome, livestock producers who want to sell meat to these lucrative markets will need to change how they use antibiotics.

pathogen: a thing that causes disease 病原体

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（来源：VOA 编辑：崔旭燕）