Flies really do spread germs, a new study confirmed.
The insects are not only annoying by trying to land on your meal or crawling over kitchen countertops, they also carry more diseases than previously thought.
And their legs and their wings are teeming with pathogens that hitch a ride after the flies land on dead carcasses or feces and then spread them to new surfaces.
Scientists studied the microbiomes of 116 houseflies and blowflies from three different continents.
They found that in some cases these flies carried hundreds of different species of bacteria, many harmful to humans.
And the risk of picking up a nasty bug increases the more people are around because city flies are more germ-ridden than their country cousins.
Professor Donald Bryant of Penn State said: “It will really make you think twice about eating that potato salad that’s been sitting out at your next picnic”
“It might be better to have that picnic in the woods, far away from urban environments, not a central park.”
“We believe that this may show a mechanism for pathogen transmission that has been overlooked by public health officials, and flies may contribute to the rapid transmission of pathogens in outbreak situations.”
Scientists had long suspected flies played a role in carrying and spreading diseases because they are all around us.
The study published in the journal Scientific Reports investigated the microbial content of individual fly body parts, including legs and wings.
The legs appear to transfer most of the microbial organisms from one surface to another.
Research director Stephan Schuster, from Singapore’s Nanyang Technological University, said: “The legs and wings show the highest microbial diversity in the fly body, suggesting that bacteria use the flies as airborne shuttles.”
“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.”
Blowflies and houseflies, both carrion fly species, are often exposed to unhygienic matter because they use feces and decaying organic matter to nurture their young.
They can then pick up bacteria that could act as pathogens to humans, plants and animals.
The study also indicated blowflies and houseflies share over 50 percent of their microbiome, a mixture of host-related microorganisms and those acquired from the environments they inhabit.
Surprisingly, flies collected from stables carried fewer pathogens than those collected from urban environments.
The researcher found 15 instances of the human pathogen Helicobacter pylori, a pathogen often causing ulcers in the human gut, largely in the blowfly samples collected in Brazil.
The known route of transmission of Helicobacter has never considered flies as a possible vector for the disease.
Professor of genetics and genomics Ana Carolina Junqueira from the Federal University of Rio De Janeiro said that the novel genomic and computational methods used for the study allowed the team an unprecedented look at the microbial community carried by flies.
Junqueira added: “This is the first study that depicts the entire microbial DNA content of insect vectors using unbiased methods.”
“Blowflies and houseflies are considered major mechanical vectors worldwide, but their full potential for microbial transmission was never analyzed comprehensively using modern molecular techniques and deep DNA sequencing.”
Source: New York Post