Results of the study were published March 21 in Environmental Science & Technology.
The study, conducted by the Bloomberg School’s Centre for a Liveable Future and Arizona State’s Biodesign Institute, looked for drugs and other residues in feather meal, a common additive to chicken, swine, cattle and fish feed.
The most important drugs found in the study were fluoroquinolones, a broad spectrum of antibiotics used to treat serious bacterial infections in people, particularly those that have become resistant to older antibiotic classes.
The banned drugs were found in eight of 12 samples of feather meal in a multistate study.
The findings were a surprise to scientists because fluoroquinolone use in US poultry production was banned by the Food and Drug Administration in 2005.
This is the first time investigators have examined feather meal, a byproduct of poultry production made from poultry feathers, to determine what drugs poultry may have received prior to their slaughter and sale.
Arsenic also found
The rendering industry, which converts animal byproducts into a wide range of materials, processes poultry feathers into feather meal, which is often added as a supplement to poultry, pig, ruminant and fish feeds or sold as an “organic” fertilizer.
In a companion study, researchers found inorganic arsenic in feather meal used in retail fertilizers.
“The discovery of certain antibiotics in feather meal strongly suggests the continued use of these drugs despite the ban put in place in 2005 by the FDA,” said David Love, lead author of the report and an assistant scientist at the Centre for a Liveable Future.
“The public health community has long been frustrated with the unwillingness of FDA to effectively address what antibiotics are fed to food animals.”
A primary reason for the 2005 ban on the use of fluoroquinolones in poultry production was an alarming increase in the rate of the fluoroquinolone resistance among Campylobacter bacteria.
“In recent years, we’ve seen the rate of fluoroquinolone resistance slow but not drop,” noted study co-author Keeve Nachman, Farming for the Future program director at the Johns Hopkins Center for a Livable Future.
“With such a ban, you would expect a decline in resistance to these drugs. The continued use of fluoroquinolones and unintended antibiotic contamination of poultry feed may help explain why high rates of fluoroquinolone-resistant Campylobacter continue to be found on commercial poultry meat products over half a decade after the ban,” he said.
All samples positive
In conducting the study, the researchers analyzed commercially available feather meal samples acquired from six US states and China for a suite of 59 pharmaceuticals and personal care products.
All 12 samples tested had between two and 10 antibiotic residues. In addition to antimicrobials, seven other personal care products, including the pain reliever acetaminophen (the active ingredient in Tylenol), the antihistamine diphenhydramine (the active ingredient in Benadryl) and the antidepressant fluoxetine (the active ingredient in Prozac), were detected.
Researchers also found caffeine in 10 of 12 feather meal samples.
“This study reveals yet another pathway of unwanted human exposure to a surprisingly broad spectrum of prescription and over-the-counter drugs,” noted study co-author Rolf Halden, co-director of the Centre for Health Information and Research and associate director of the Swette Centre for Environmental Biotechnology at Arizona State.
Select for resistance
When researchers exposed several strains of E. coli bacteria to the concentrations of antibiotics found in the feather meal samples, they also discovered that the drug residues could select for resistant bacteria.
“A high enough concentration was found in one of the samples to select for bacteria that are resistant to drugs important to treat infections in humans,” Nachman noted.
“We strongly believe that the FDA should monitor what drugs are going into animal feed,” Nachman said. “Based on what we’ve learned, I’m concerned that the new FDA guidance documents, which call for voluntary action from industry, will be ineffectual. By looking into feather meal, and uncovering a drug banned nearly six years ago, we have very little confidence that the food animal production industry can be left to regulate itself.”