Swarms of flies could be used to help monitor disease outbreaks, says an international team headed by researchers at Nanyang Technological University in Singapore.

Common house-flies and blowflies provide ’free-rides’ to whole communities of bacteria, known as a microbiome, helping in transferring the bacteria to any surface the flies land on.

By sequencing the genetic material of 116 houseflies and blowflies along with all the microorganisms that they are carrying, the team found that each of these flies carried up to several hundred different species of bacteria, some of which were harmful to humans.

One of these, Helicobacter pylori, is a pathogen that can cause stomach ulcers in humans and is the strongest known risk factor for gastric cancer. Although known to be spread via body fluid and smear infections, this is the first time that H. pylori has been shown to be spread via flies in the environment.

The research team believes that their new technique could put flies into service in public health surveillance programs. They suggest that germ-free flies, bred without any microorganisms in their microbiome, could pick up latent microbiomes in any environment they are released into. When these flies are recaptured using bait traps, their microbiomes can be sequenced, giving clues to the type of bacteria they have encountered in the environment, thus acting as an early warning system.

Such 'autonomous bionic drones' could be particularly useful in agriculture where it could, for instance, be used to detect a plant pathogen before it causes an outbreak. Farmers could then organize a targeted treatment that only eradicates that pathogen, leaving the other parts of the ecosystem intact, said the team behind the study