Much Worse Than We Ever Knew

HOUSEFLIES ARE BACTERIA-LADEN SHUTTLES, POTENTIALLY TRANSFERRING THE MICROORGANISMS ONTO YOUR FOOD. DIN MOHD YAMAN/SHUTTERSTOCK

We all know that with their penchant to feast on rotting flesh and partiality for poop, flies are pretty unhygienic creatures. It now seems that we have been underestimating just how gross these insects are, if that is even possible.

A new study published last week in Scientific Reports has found that both houseflies and blowflies are a positive haven for bacteria, with some insects carrying hundreds of different species on their wings and legs, depositing them where they land, be it the surfaces in your kitchen or the sausage rolls at your picnic. Many of these bacteria can have a significant impact on human health, and as a result, the authors argue that health organizations have been overlooking the role the insects may play in disease outbreaks.

“The legs and wings show the highest microbial diversity in the fly body, suggesting that bacteria use the flies as airborne shuttles,” explained Stephan Schuster, who coauthored the research. “It may be that bacteria survive their journey, growing and spreading on a new surface. In fact, the study shows that each step of hundreds that a fly has taken leaves behind a microbial colony track, if the new surface supports bacterial growth.”

The team sequenced the microbiomes of 116 houseflies and blowflies from three different continents to build up a picture of the diversity of microorganisms that live on the insects, and even the researchers were stunned by what they found. They discovered that overall, the creatures harbored over 600 different types of bacteria, with many of these being linked to human health. Interestingly, they found that the flies sampled from horse stables had a lower diversity of bacteria on their bodies than those from urban environments.

It is well known that flies can transmit diseases, but up to now scientists had no idea just how extensive this can be. For example, the researchers discovered 15 flies that were carrying the bacteria Helicobacter pylori, which is known to cause stomach ulcers in humans. Until now, flies have never before been considered a vector for Helicobacter.

While this obviously has important implications for human health, with the researchers suggesting that perhaps the next time you have a picnic, choose a spot in the woods rather than that park in the middle of the city, it could have some other exciting applications.

The insects could be used as natural biomonitoring “drones”. The authors suggest that flies could be sent into certain regions that might be hard to sample, and then the microbiomes of the insects tested to see what microorganisms are present.