via Wikimedia Commons

Of all the huge systemic problems we’re refusing to face—the oceans are rising, income gaps are widening, political discourse has devolved to sub-Great Ape levels of sophistication—one of my least favorites is hearing about how we’re racing toward a “post-antibiotic era.” And yet the signs are all around us—antibiotic-resistant bacteria are found in our livestock and in our noses, and now they’re even falling to Earth in crow shit.

A new study found antibiotic-resistant genes in the droppings of 2.5 percent of crows sampled across the United States—not a huge number but it’s discouraging to find genes riding animals that roam so widely. Bacteria readily swap genes, and resistance genes are already spreading faster than the CDC expected. Riding on the wings of crows is another way for resistance genes to spread, in addition to riding around in people.

This isn’t the first time that evidence of multi-drug resistance spreading among wildlife has been discovered. In 2012, researchers in Iowa found a resistant strain of Staphylococcus aureus in rabbits and a bird. Earlier this year in Botswana, 57 percent of banded mongooses sampled by Virginia Tech researchers were found to be carrying antibiotic-resistant E. coli. Environmental Health News reports that, “in addition to crows, resistance genes have been detected in gulls, houseflies, moths, foxes, frogs, sharks and whales, as well as in sand and coastal water samples from California and Washington.”

In Europe, 25,000 people die every year from antibiotic-resistant bacteria; in the United States bugs that don’t respond to drugs make 2 million people sick every year. Microbial evolution is gaining an upper hand against us after not-quite a century of being beaten back by our penicillin silver bullets. 

And we don’t have new antibiotics coming down the pipeline, leading to headlines like this one from The Guardian, which asks “Are you ready for a world without antibiotics?” The WHO warns that the spread of anti-microbial resistance “threatens a return to the pre-antibiotic era,” when things that are easily treated now, like bacterial meningitis or urinary tract infections, frequently became fatal.

Antibiotic resistance might be spreading to wildlife through waste sites or through livestock; the resistant genes found in crows indicate a human clinical source.

“Because birds are so mobile, it’s possible they may acquire resistance genes from multiple sources in their travels,” said Julie Ellis, a research scientist at Tufts University. “Maybe they visit a dumpster or sewage treatment plant one day and later a farmer’s field.”

One thing that’s not yet clear, though, is how the spread of antibiotic resistance through wildlife could affect public health. Once introduced in wildlife, could the drug-resistance work its way back up the food chain to people? Could it spread through passing exposure? Diseases pass between people and animals with some frequency, and there’s a growing disquiet that we might soon reap what we’ve unwittingly sown.