At a global level, flies (dipterous insects) are known as highly concentrated vectors in urban areas and propagators of disease-causing pathogens; mainly gastrointestinal and ophthalmic, dangerous for the healthy well-being of humans and even domestic animals.
The interaction of flies and humans in the public sale of food is frequent. This is because they move all day from one place to another in search of a balanced diet and preferably liquid, easy to dissolve in their saliva.
Flies are attracted to the products of decomposing organic matter, the remains of food in garbage dumps, milk and food for human consumption.
The organizations that regulate health and public health have registered 21 species of flies, as causative agents of gastrointestinal diseases, due to their predilection for contaminated environments and endophilia, that is, tendency to enter buildings (Graczyk et al., 2005).
Flies are capable of efficiently transporting the microorganisms that cause diseases in five ways:
- In its mouth pieces,
- Through the vomit,
- In the hairs of the body and legs,
- On the viscous pads the legs,
- In the intestinal system by means the faeces (Radvan, 1960).
The microorganisms isolated in a study carried out with food samples from several types of restaurants corresponded to: bacteria, 46.8% (Escherichia coli, Klebsiella pneumoniae); followed by parasites, 31.9% (Entamoeba histolytica and Blastocystis hominis) and fungi, 21.3% (Aspergillus fumigatus and Cryptococcus spp).
The domestic fly has been confirmed as an efficient vector of E. coli, specifically, strain O 157: H7. This strain can be transported in the digestive tract, multiply in the mouth pieces and then excreted for three consecutive days (Moissant et al 2004, Sasaki et al 2000).
Infection with E. coli 0157: H7 is associated with hemolytic uremic syndrome, a disease characterized by the destruction of red blood cells, a drastic reduction in platelets and acute renal failure (Murray et al., 2002). .
Flies pose a serious threat to the work efficiency of the staff. A local infested with flies causes more than 50% of employees to spend their time killing and driving away flies. In turn, the bites (although not all flies bite, those that do have poisonous particles in their saliva) and the annoying buzz of these interrupt the tranquility of the diners and chase them away. Nobody wants to eat a plate of contaminated food that immediately interferes with their daily work and recreational activities by causing annoying gastrointestinal effects.
An example of how infectious spread occurs would be the following: A housefly feeds on human feces in a latrine used by a typhoid carrier, and then perches on a meat salad being prepared in a restaurant. The fly inoculates the food with pathogenic bacteria (including Salmonella typhi, the bacillus of typhoid) through its buccal system, vomit, legs and hair contaminated with human feces; multiplying rapidly in that ideal medium.
Hours later, when the customers of the restaurant consume the meat salad, they acquire the infection and develop typhoid fever.