Scientists have been sounding the alarm about growing antibiotic resistance resulting from overuse of the drugs in healthcare settings and, even more, among commercial livestock. They’ve now made an even more alarming finding: antibiotic resistance is spreading to wildlife.
Tufts University researchers have discovered that crows carry a gene that makes them resistant to antibiotics. Figuring this out required getting samples from the birds and from a lot of them. To do this, Julie Ellis, a research scientist at Tufts University’s veterinary school, collected droppings by placing a large tarp under trees in Worcester, Massachusetts, where the crows were known to roost.
She and other researchers collected nearly 600 fecal samples in Massachusetts, Kansas, New York and California. After testing, they found that 15 of the crows (about 2.5 percent) from all the states except California had genes resistant to vancomycin, which is used to treat life-threatening infections that have not responded to other medicines.
Even more troubling is that the vancomycin resistant genes found in the crows are also resistant to other types of antibiotics commonly used among livestock and humans. Plus, the crows’ genes contain the “signature of human clinical source.”
The Rise of Antibiotic Resistance in Humans and Livestock
The presence of antibiotic-resistant genes in wildlife could lead to even greater resistance to the drugs as “superbugs” — bacteria resistant to antibiotics — evolve. Antibiotic resistance means that diseases, including tuberculosis, that have been curable may cease to be. Antibiotic resistant strains of salmonella, E. coli and gonorrhea already exist. Every year, two million people became sickened with infections resistant to antibiotics and 23,000 die from such infections in the United States, according to the Centers for Disease Control and Prevention.
The CDC estimates that as much as 50 percent of antibiotics prescribed to people are unnecessary. An even greater source of concern has been the excessive (30,000 tons a year) amount of drugs given to cattle in commercial agriculture to spur their growth. A report released by the CDC in September describes a “link between antibiotic use in food-producing animals and the occurrence of antibiotic-resistant infections in humans.” The CDC calls for antibiotics to “be used in food-producing animals only under veterinary oversight and only to manage and treat infectious diseases.”
How Do Wild Animals Become Resistant to Antibiotics?
How crows and other wildlife (including rooks wintering in Europe, houseflies, foxes, and mongooses in Botswana) became resistant is not certain. Scientists point to agriculture as a possible source. As Ellis notes, “because birds are so mobile, it’s possible they may acquire resistance genes from multiple sources in their travels. Maybe they visit a dumpster or sewage treatment plant one day and later a farmer’s field.”
One study of red-billed choughs in Spain specifically notes that “when manure from medicated livestock and urban effluents is spread onto agricultural land, both residues of antibiotics and bacteria carrying antibiotic resistance may be introduced into the environment.” The study links agricultural manuring to anti-microbial resistance in the choughs.
Findings like those of Ellis are all the more reason to push for legislation like the Preservation of Antibiotics for Medical Treatment Act. Senator Barbara Boxer and Congresswoman Louise Slaughter have introduced this bill repeatedly but Congress has refused to pass it each time.
“No doubt lobbyists representing agribusiness and the pharmaceutical companies that supply it have a role in that,” as Care2 blogger Piper Hoffman wrote. The discovery of antibiotic resistance in wildlife makes it all the more pressing to call for the drugs to only be used for medical treatment in humans and in animals.
Photo from Thinkstock