Most strains of the bacterium Escherichia coli are harmless and live in the intestines of healthy humans and animals. A few strains can cause illness. One strain, called E.coli
O157:H7, produces a powerful toxin and can cause severe illness, including bloody diarrhea, in people. In the young and the elderly, the disease can be life threatening. Outbreaks of disease from this organism are a
E.coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea traced to contaminated hamburgers. Most
cases since then were caused by eating undercooked beef. However, large outbreaks of this illness have been traced to raw alfalfa sprouts, lettuce, and spinach, and smaller outbreaks to unpasteurized milk, juice, and cider.
Many medical entomologists believe that two flies, the house fly and the fruit fly may be transmitting E.coli O157:H7 onto food used for human consumption. Research has demonstrated that house flies pick up the bacteria on their feet and body hairs when they come into contact with animal feces, and then carry the bacteria to new sites. For example, a fly may walk across feces, fly a hundred yards, and land on the plate of barbecued ribs you’ve just placed on your deck, leaving bacteria behind. This type of disease transmission is called mechanical transmission because the fly simply carries the bacteria on its body to a new location.
Flies can also transmit bacteria in another way, when they swallow it. This is more than simple mechanical transmission of disease. The ingested bacteria are harbored in the intestines of flies and continue to be excreted in their feces for at least three days after feeding. Flies can “poop” bacteria wherever they are, on any surface, whether it’s on your kitchen counter or your baby’s pacifier. The bacteria can also grow and reproduce in the mouthparts of the fly. That’s important because flies are constantly touching surfaces with their sponging “tongues” and leaving bacteria behind.
It’s not just the house fly that transmits E. coli bacteria. Researchers from USDA found that the common fruit fly is an effective carrier of the bacteria and a possible cause of contamination in apples. While reports of apple cider contaminated with E.coli O157:H7 are rare, researchers have found that bacteria transmitted by fruit flies grew rapidly in the wounds of apples.
Good fly control in restaurants, stores, and other areas where food is prepared, stored, and eaten can reduce the risk of contamination with E.coli O157:H7, as well as other types of disease organisms. This is just one way in which professional pest control protects the health of the nation.