Warning: If you are about to eat some food, this may ruin your meal. Did you know that when flies land on food to eat some of it, they vomit on it first?
This vomit contains traces of what they had previously eaten, whether it was a bit of someone else’s lunch, or something much less palatable, such as dog poo.
Now scientists are warning that we should be much more aware of the risks associated with the common housefly and their vomit on our food.
Researchers at the University of Massachusetts Amherst looked at the risks associated with “synanthropic” flies, the common flies that don’t bite us and live with us.
They say that while scientific research has largely focused on biting flies like mosquitoes that herald disease, spreading it by transferring infected blood from host to host, these synanthropic flies may pose an even greater threat.
“I’ve been working with synanthropic flies since I was a graduate student in the 1960s,” said John Stoffolano, a professor of entomology at UMass Amherst’s Stockbridge School of Agriculture, who is the author of the research published in the journal Insects.
“And synanthropic flies have been largely ignored. Bleeding flies have taken the spotlight, but we should pay attention to those that live among us because they get their nutrients from humans and animals that shed pathogens in their tears, feces and wounds.” .
What flies eat before they land on your food
He explained that the common housefly flies around and nibbles on various types of highly unpalatable food, which can include things like roadkill, animal poo, rotting garbage and sewage.
When it eats, it fills the crop — which Stoffolano said “is like a gas tank” — but it’s a place for storage, not for digestion, so there are few digestive enzymes that would normally destroy most pathogens.
The crop is “a place to store food before it enters the digestive tract where it will be converted into energy for the fly,” he said.
When the fly wants to eat another morsel, it spits up liquid from the crop onto the surface of the food as part of the eating process.
According to Stoffolano, because of the nasty things flies store in their crop, it can inadvertently become a place to store disease-producing pathogens.
Worse perhaps, the crop is also a place where microbes develop antibacterial resistance, which can spell disaster for humans who become infected with a pathogen.
“It’s the little things that cause the problems,” says Stoffolano. “Our health depends on paying more attention to these flies that live with us”.
The authors of the paper warn that the area needs “a lot of focused study”, as not enough is currently known about the importance of flies regarding the spread of disease and potential antibacterial-resistant microbes.