Have we underestimated flies as a disease transmission vector?
A chracterisation of the microbiome of blowflies reveals they could be a transmission route for a number of diseases
In the movies, the presence of flies means one thing, that the plucky detective is about to uncover something rather grizzly. For centuries, flies have been an omen of decay and putrefaction and they earned that reputation. Rancid odours, decaying food, and effluent would always be accompanied by an entourage of flies.
So, what happened? Today files seem to be more of a minor annoyance that a sign of something nasty. We flick them away from food at a picnic while muttering under our breath, but we never really believe they could do us any harm. After all, they’ve just been flying around the garden, not rotting flesh.
Research done at SCELSE with collaborations around the world suggests that maybe we are doing flies a disservice. An article published in Scientific Reports this month describes one of the only studies to fully characterise the microbiome of a large sample of blowflies. The study revealed that flies can harbour some pretty serious pathogens, including Helicobacter pylori.
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.”
Stephan Schuster, research director 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.”
The study shows that perhaps we should be more careful with flies around food, but more importantly, that blowflies could be routinely monitored as a way to track and control disease.
Blowflies and houseflies are mechanical vectors inhabiting synanthropic environments around the world. They feed and breed in fecal and decaying organic matter, but the microbiome they harbour and transport is largely uncharacterized. We sampled 116 individual houseflies and blowflies from varying habitats on three continents and subjected them to high-coverage, whole-genome shotgun sequencing. This allowed for genomic and metagenomic analyses of the host-associated microbiome at the species level. Both fly host species segregate based on principal coordinate analysis of their microbial communities, but they also show an overlapping core microbiome. Legs and wings displayed the largest microbial diversity and were shown to be an important route for microbial dispersion. The environmental sequencing approach presented here detected a stochastic distribution of human pathogens, such as Helicobacter pylori, thereby demonstrating the potential of flies as proxies for environmental and public health surveillance.
The microbiomes of blowflies and houseflies as bacterial transmission reservoirs
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
Scientific Reports 7, Article number: 16324 (2017)