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Research in entomopathology has always been more interested in biting insects, especially blood-sucking ones, which are carriers of serious and even fatal diseases. The mosquito, for example, would be the most human-killing animal in the world. Pathological involvement of other insects a priori Harmless is still very little studied, a new study published in the journal insect pointed out that the housefly may potentially pose a greater threat to humans (than the mosquito). Consuming only liquid, these insects would regurgitate their food to pre-digest it and thus could carry dangerous pathogens.
There are more than 80,000 different species of flies worldwide, with morphology varying greatly from species to species. Some can bite and feed on human or animal blood, tearing off (with their mandibles) a piece of flesh to enter the capillaries. Others feed only on flesh torn off by its decomposition or simply feed on decaying organic matter. Some also have a very specific diet, such as the cherry fly, which, as its name suggests, feeds exclusively on cherries.
Housefly: potentially more dangerous than mosquitoes
Without mandibles, “non-biting” flies feed exclusively on liquid. After landing on solid food, they would first regurgitate a mixture of saliva and predigested food remains to preliminarily break them down and suck them up drop by drop with their paws.
According to scientists from the University of Massachusetts, houseflies would be the most feared because, being omnivores, they land and feed on anything that can provide them with nutrients and energy. Abundant in both rural and urban areas, it can get on fresh or spoiled food, patient secretions, stool, etc. It is particularly attracted to warmth and certain odors such as sugar and decay.
Each time they eat, they regurgitate some of what they previously consumed, including pathogens (contained in, for example, feces). They fill a kind of pocket like a reservoir that would serve mainly for storage and not digestion. This pocket serves them both as a storehouse of enzymes that they spit out to break down their food in advance, and also as a storehouse of food — which then passes into another pocket intended for digestion.
The pathogenic agents that they can suck up are therefore not completely digested, the storage pocket is equipped with only a few enzymes. Also, that they are covered with all the decomposed matter that they land on (and subsequently land on us or on our food). Although blood-sucking flies and other biting insects with direct access to the bloodstream are often considered more dangerous, “we must be wary of those who live among us because they get their nutrients from humans and animals that release pathogens, excrement into their tears and their wounds,” warns John Stoffolano, professor of entomology at the University of Massachusetts and lead author of the study.
Because of this, the housefly can easily transmit diseases such as cholera, salmonellosis, typhoid, tuberculosis, etc. In addition, some flies that have developed resistance to insecticides could harbor antibiotic-resistant pathogens.
An important member of the ecosystem
However, it should be noted that despite the generally negative perception of the fly, it is part of an important ecosystem service. Due to its consumption of decomposing organic matter, it plays an important role in the disposal of waste, which later feeds other insects or brings nutrients to the soil for plants. The fly is also one of the pollinators and contributes to the reproductive cycle of plants.
On the other hand, it is also part of a food chain that includes many species such as birds, batrachians, arachnids, etc. Efforts to eradicate it would thus disturb the basic balance established in the biosphere for thousands of years.