These days, there’s more and more doom-and-gloom information about multidrug-resistant bacteria. They’re in our hospitals, medical tourists, people on the street, our pets, our food, and pretty much anywhere else you can think of. We can now add crow poop to the list too.
It’s almost to be expected, really. We know that birds can carry various resistant bacteria, and the more contact birds have with human environments and food animal environments, the greater the chance these bacteria are going to be transmitted between them (in one direction or another). It’s important to remember that resistant bacteria are also present in nature, independent of human activities.
A recent report of a pretty high profile multidrug-resistant bacterium – vancomycin-resistant Enterococcus (VRE) – in birds wasn’t all that surprising. The study (Oravcova et al, Environmental Microbiology 2013) reported finding enterococci carrying the vanA resistance gene in 2.5% of 590 crows sampled in multiple US states. It was quite interesting though, because VRE is (in North America) a human-associated bacterium. It’s a little more muddled in Europe where VRE was an issue in food animals, in part due to former use of a drug related to vancomycin (avoparacin) in some food animal species. Here though, we rarely see VRE in anything species but humans. This raises some interesting questions about where these crows picked up VRE, if they are able to carry the bacterium for long periods of time, and if they can act as a source of human or animal infection.
Does this bother me? No. It’s of academic interest, but not something that’s going to pose a real risk to me. I tend not to walk under trees full of crows with my mouth open, and I’m pretty sure I’d wash my hands if a crow pooped on them. Yes, there’s the chance that I could have unnoticed contact with contaminated crow poop remnants on an outdoor surface, but the odds of it containing viable VRE are pretty low, and there are lots of other things that I’m more likely to pick up in my daily activities. In terms of VRE, I’m presumably more likely to be exposed in other ways than from crows. However, the study is still important in that it shows how widespread antimicrobial resistance is, how complex the issue is and how we need to do more to understand the ecology and epidemiology of various resistant bugs.
There’s no need to go exterminating crows, but Johnny Depp may want to consider an alternative style of hat.