1. Introduction
The U.S. Food and Drug Administration (FDA) has classified flies as filth adulterants and requires the exclusion of flies and other pests from food and from
establishments that manufacture, pack or store food products. Flies are also considered to be mechanical vectors of various pathogens such as bacteria, protozoa, and viruses. The housefly (Musca domestica) is categorized by FDA as an important contributing factor in the dissemination of various infectious foodborne
diseases such as cholera, shigellosis and salmonellosis (Olsen et al., 2001).
Adult house flies have been demonstrated to transmit pathogens from the
sponging mouthparts, through vomitus, on body and leg hairs, on the sticky parts of the feet, and through the intestinal tract. Microorganisms on the fly’s body are disseminated by direct contact, in fly feces and through the air for short distances from insect-electrocuting traps (Olsen, 1998).
The sources of approximately 25% of epidemics of foodborne illnesses reported each year are unknown. Foods contaminated by flies may contribute to some of these epidemics. In an epidemic of enterohemorrhagic colitis in a nursery school in Japan, Escherichia coli O157:H7 was isolated from both patients and houseflies collected in the area and all isolates were indistinguishable by molecular typing methods.
Flies were traced back to a cattle farm located near the nursery school
Other studies have shown that pathogen-carrying flies travel between pathogen reservoirs and exposed foods. In Mexico it was demonstrated that houseflies transported Salmonella from slaughterhouses to nearby markets and residential areas (Greenberg et al.,1963).
An earlier study found houseflies transporting
Salmonella enteritidis from a sewage pool to a kitchen