Houseflies Carry More Dangerous Bacteria Than Previously Believed

Houseflies carry as many as several hundred different species of bacteria, some of which may be harmful to humans, new research shows. The international research team behind the study, led by Nanyang Technological University in Singapore, also proposed that swarms of flies can be used to help monitor disease outbreaks.

The researchers sequenced the genetic material of 116 houseflies and blowflies along with all the microorganisms that they are carrying.

One of the bacteria found, 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 by body fluid and smear infections, this is the first time that H. pylori has been shown to be spread by flies in the environment.

Hitching A Ride

The study follows up on research that shows how whole communities of bacteria, known as a microbiome, can “hitch a ride” on common carrion flies and can be transferred to any surface where the flies land.

“Our study has shown that bacteria can ‘fly’ by hitching a ride on common flies. They pick up the microbiome on their feet, spread them across their wings in a similar way like how we might comb our hair, and then proceed to disperse them on surfaces that they land on.”

said team leader Professor Stephan Schuster, a research director at the Singapore Centre for Life Sciences Engineering (SCELSE) at NTU Singapore.

Dr Ana Carolina Martins Junqueira, a molecular entomologist who co-led the research, said flies are an important part of nature’s eco-system, as they are also pollinators like bees.

“Carrion flies have microscopic hairs on every part of the body excluding the eye and these bristles make them the perfect carrier for pollen and also bacteria. It is an evolutionarily optimised vehicle for the dispersal of microorganisms in the environment,”

said Dr Junqueira, a faculty member at the Federal University of Rio de Janeiro.

Health Surveillance

The team envisions their new technique putting flies into public service in health surveillance programs.

Germ-free flies, bred without any microorganisms in their microbiome, could pick up latent microbiomes in any environment they are released into, because they are tiny enough to enter even the smallest of cracks and crevices.

housefly metagenomic dataset

Summary of sampling datasets, data generation and analyses.
Blowflies (nā€‰=ā€‰62; 1 control) and houseflies (nā€‰=ā€‰53) were collected in individual vials and immediately placed on dry ice until DNA extraction.
Samples were individually sequenced in a multiplexed run, generating a total of 6,759,843,350 reads for both fly species.
The blowfly draft genome generated in this study and the housefly reference genome were used as filters to remove host-related reads.
Final metagenomic dataset included a total of 3,009,429,390 reads for 116 flies.
Credit: Ana Carolina M. Junqueira, et al. CC-BY

When the 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 if we want to detect a plant pathogen outbreak. Through regular monitoring, if we know that a particular pathogen is affecting the crops and is becoming an outbreak, then farmers could organise a targeted treatment that only eradicates that pathogen, leaving the other parts of the ecosystem intact.

To date, diseases transmitted by a mechanical vector like flies have been a major overlooked pathway by both the medical and academic community. This is a great example of how observations from basic research on how diseases spread might be translated into viable and useful applications, opening up new avenues for future technology,”

said Prof Schuster.

The work was funded by the Singapore Ministry of Education Academic Research Fund, the Singapore Centre for Environmental Life Sciences Engineering, the National Research Foundation Singapore, Ministry of Education, Nanyang Technological University, and National University of Singapore.

Ana Carolina M. Junqueira, Aakrosh Ratan, Enzo Acerbi, Daniela I. Drautz-Moses, Balakrishnan N. V. Premkrishnan, Paul I. Costea, Bodo Linz, Rikky W. Purbojati, Daniel F. Paulo, Nicolas E. Gaultier, Poorani Subramanian, Nur A. Hasan, Rita R. Colwell, Peer Bork, Ana Maria L. Azeredo-Espin, Donald A. Bryant, Stephan C. Schuster
The microbiomes of blowflies and houseflies as bacterial transmission reservoirs
Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-16353-x

Image: Jacob Martin/Flickr