If you grew up watching the same cartoons that I did, you know that when you ask the waiter what a fly is doing in your soup, he’s supposed to squint intensely, then shrug and say, “The backstroke.” But, according to scientists, the more accurate response would be “The backstroke, and also spreading even more disgusting bacteria than we previously thought possible.”
A team of researchers from Penn State’s Eberly College of Science used DNA sequencing to study the microbes that were found on the bodies, legs, and wings of houseflies and blowflies, and learned that in addition to being gross, they’re also seriously EXTREMELY gross. More than 350 kinds of bacteria were found on the bodies of houseflies, including E. coli and salmonella, and the blowfly also carried Helicobacter pylori, a type of bacteria that can cause stomach ulcers.
“People had some notion that there were pathogens that were carried by flies but had no idea of the extent to which this is true and the extent to which they are transferred,” Dr. Donald Bryant, a professor of biochemistry and molecular biology at Penn State, said. “We believe that this may show a mechanism for pathogen transmission that has been overlooked by public health officials.”
The 116 houseflies and blowflies that were studied were collected from three different continents, in urban, rural, and natural settings. They learned that the insects’ wings and legs were covered with the “highest diversity” of bacteria, which is something that you’ll remember the next time you see a fly put its nasty little feet on your food. “It will really make you think twice about eating that potato salad that's been sitting out at your next picnic," Bryant said.
According a housefly fact sheet prepared by Penn State’s Department of Entomology, flies were already known to transmit more than 60 diseases to humans, including dysentery, cholera, anthrax, and tuberculosis. Why? Because they’re disgusting. Both houseflies and blowflies are carrion fly species, meaning that their own diets can include “fecal matter, discharges from wounds and sores, sputum, and [...] spoiled fish, eggs and meat.” (And it’s worth noting that the 15 blowflies that carried Helicobacter pylori were found in Brazil; the researchers believe that they picked it up from open sewage sites or outdoor toilets).
So what can you do to prevent flies from touching your food? Well, you could just eat inside forever. But if the idea of a picnic is still irresistible, Bryant suggests taking your basket and your blanket into the woods instead of eating in a central, urban park. Although this research is both important and gag-inducing, it shouldn’t really incite panic. I mean, chances are, you’ve eaten something that a fly tap-danced on (or did the backstroke through) and you’re still OK, right? Right.