Researchers report that they have found evidence of banned antibiotics in poultry byproducts, suggesting that growers are evading a 2005 prohibition on their use in treating chickens and turkeys.
Scientists at Johns Hopkins' Bloomberg School of Public Health and at Arizona State University detected fluoroquinolones, broad-spectrum antibiotics used to treat bacterial infections in people, as well as otherover-the-counter drugs and residues in feather meal, a common additive to chicken, swine, cattle and fish feed.The Food and Drug Administration banned the use of fluoroquinolones in poultry production in 2005 amid concern about the spread of antibiotic-resistant bacteria. But in a study published in Environmental Science & Technology, the two schools' researchers report they found the banned drugs in 8 of 12 samples of feather meal collected from six states and China.
"It’s concerning to see that banned drugs are being fed to chickens," said David C. Love, the study's lead author and a microbiologist with Bloomberg School's Center for a Livable Future. "They were banned for obvious health reasons."
Study co-author Keeve Nachman, also from Hopkins' Center for a Livable Future, noted that the FDA had outlawed fluoroquinolones in poultry production because of what he called an alarming increase in resistance among Campylobacter bacteria.
"With such a ban, you would expect a decline in resistance to these drugs," Nachman said in a press release about the study. The continued use ofthe drugs and unintended contamination of poultry feed may help explain why high rates of resistant bacteria are found on commercial poultry meat products years after the ban, he added.
This is the first time researchers have checked feather meal, a byproduct of poultry production made from feathers, to see what drugs the birds may have received before being slaughtered and sold to consumers. Love said they did so because feathers tend to accumulate antibiotics more than the birds' meat does.
Nearly 9 billion broiler chickens and 80 million turkeys are raised annually in the United States, and about a third of each bird's weight, including feathers and bones, winds up being recycled into pet food, poultry feed and fertilizer.While just two-thirds of the feather meal samples contained the banned drugs, all 12 had residues of from two to 10 antibiotics. Other drugs also were detected, including the active ingredients in the antidepressant Prozac and such over-the-counter medicines as Tylenol and Benadryl. Ten samples also contained caffeine.
Love said researchers checked those findings with poultry farmers, who said the drugs are occasionally given to birds to treat them for vaccine reactions and respiratory problems. Caffeine also is given to keep the birds awake and feeding, he said.
UPDATE: A spokesman for the National Chicken Council suggested in emails that the antibiotics and other substances detected were traces left over from past use of the products, or even cross-contamination from faulty sample collection. Tom Super, vice president of communications for the industry group, said that "modern testing methodologies, like those used in these studies, are extremely sensitive and can detect bioaccumulation of just about anything - even if the product or compound has not been used in years."
The researchers also reported in a separate publication that the feather meal samples they analyzed were high in arsenic, including the highly toxic inorganic form. Until last July, most chickens were fed the veterinary drug roxarsone, which contains arsenic, to treat a parasitic disease and plump them up. The drug's maker, a subsidiary of Pfizer Inc., voluntarily suspended sales after the Food and Drug Administration found low levels of inorganic arsenic, a carcinogen, in livers of treated chickens.
Arsenic was detected in all 12 feather meal samples, which were collected at a time when roxarsone was still being used, said JHU's Nachman. While some forms of arsenic are more toxic than others, the inorganic forms made up 37 to 83 percent of all the arsenic detected, the study found.
The chicken council also dismissed this finding, saying that since arsenic occurs in nature, it's not unexpected that birds might pick it up on their feathers. The analysis did not detect roxarsone itself, Nachman acknowledged, but he said researchers suspect that the drug breaks down in the animals' gut so would not show up in the feathers.