New research on "synanthropic" flies, or non-biting flies that live with people, suggested that we should pay much more attention to them as disease vectors.
While epidemiologists have concentrated on biting flies, which may spread illnesses by moving contaminated blood from host to host, it has been shown that what non-biting flies regurgitate poses a considerably larger risk to human health.
Why you should pay attention to fly vomit
Erik Karits/Unsplash
"I've been interested in synanthropic flies since I was a graduate student in the 1960s," said John Stoffolano, professor of entomology at UMass Amherst's Stockbridge School of Agriculture and author of recent research published in the journal Insects, as per ScienceDaily.
Synanthropic flies have mainly gone unnoticed.
Blood-feeding flies have received a lot of attention, but we should also pay attention to the ones that dwell among us since they derive their nourishment from people and animals that shed diseases in their tears, excrement, and wounds.
Consider the ordinary house fly to demonstrate the point.
It may eat a variety of delicacies while buzzing in and out of your house throughout the day, including roadkill, animal feces, decaying waste, and fast excursions to the sewage smorgasbord.
It swells its crop every time it eats.
The crop is like a gas tank, Stoffolano explained, a place to store food before it makes its way into the digestive tract where it will be converted into energy for the fly.
Because the crop is a place for storage rather than digestion, there are few digestive enzymes or antimicrobial peptides at work, both of which would neutralize most pathogens.
As a result, the crop accidentally becomes a repository for disease-causing microorganisms.
When the flight takes off, say, with a crop full of new dog poo left on the pavement, it gets rid of surplus water in its crop by "bubbling," or regurgitating the water out, misting everything it comes into touch with.
Assume the same fly enters via your window and settles on the sandwich you're cooking.
It regurgitates part of what's left in its crop onto your bread before helping itself to a bite of your grinder. Along with the crop contents, whatever viruses that fly a chance to absorb earlier are released.
It only gets worse. Because a fly's crop is one of the breeding grounds for antibiotic resistance, whatever is spit onto your food may not respond well to standard therapies.
Even then, as Stoffolano pointed out, we still don't know a lot about these insects.
How strong are the immune systems of various synanthropic flies, for example?
Do flies incubate and promote the growth of hazardous viruses in their bellies, or do they just convey illnesses from one location to another?
Are female or male flies stronger disease transmitters? How do crop quantities differ depending on the species?
The common housefly is one of the most prevalent insects and has the capacity to transmit illness to humans, as per NEHA.
This fly is ubiquitous in homes and restaurants across the United States.
It is regarded as a larger hazard to human wellbeing than any other non-biting fly species due to its intimate contact with people and capacity to spread disease.
They have the ability to carry over a million germs on their body and transmit them to contaminate surfaces and food.
Pathogens that cause shigellosis, typhoid fever, E. coli and cholera can be transmitted by the common housefly.
The disease-causing chemicals can be conveyed by body hairs or tarsi, which are transferred to food or surfaces when the fly settles.
Pathogens can also be transferred when a fly regurgitates onto food to liquefy material for digestion.
The fly's life cycle begins with the egg and larval stages. These two phases emerge from animal and vegetable waste.
Eggs can hatch in as little as 24 hours under ideal conditions. Fly larvae (maggots) are roughly 1/2 inch long and creamy-white in appearance.
This stage lasts 4-7 days, during which time the shell hardens and darkens. This is the start of the pupal stage.
