Flies may be more than pesky picnic crashers as researchers have found that they could also carry hundreds of bacteria harmful to humans and play a role in spreading diseases.
Because flies often live close to humans, scientists have long suspected they played a role in carrying and spreading diseases, but this study, published in the journal Scientific Reports, adds further proof of that threat.
“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,” said Donald Bryant, Professor at Pennsylvania State University in the US.
The researchers examined 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 of which are harmful to humans.
“The legs and wings show the highest microbial diversity in the fly body, suggesting that bacteria use the flies as airborne shuttles,” said Stephan Schuster from Nanyang Technological University, Singapore.
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, where they could pick up bacteria that could act as pathogens to humans, plants and animals.
The study also indicates that 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 findings showed.
The researchers found 15 instances of the 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, said Schuster.
Flies may not be all bad, however. The researchers suggest they could turn into helpers for human society, perhaps even serving as living drones that can act as an early-warning system for diseases.
“For one, the environmental sequencing of flies may use the insects as proxies that can inform on the microbial content of any given environment that otherwise would be hard or impossible to sample,” said Schuster.
“In fact, the flies could be intentionally released as autonomous bionic drones into even the smallest spaces and crevices and, upon being recaptured, inform about any biotic material they have encountered,” Schuster added.