FLY SUPPLEMENT: Study Finds New Fly Pathogens

A new study funded by Orkin Pest Control, Atlanta, Ga., reveals that common house flies carry a bacteria that has been linked to meningitis. This is the first time the bacteria, Acinetobacter baumanni, has been detected from flies. For pest professionals who perform fly control services, this study has significant public health ramifications.

The other newly detected pathogens were Bacillus pumilus, which can cause food poisoning, and Enterobacter sakazakii, which can cause urinary tract, pulmonary and bloodstream infections. Further scientific research is needed to determine whether any of the newly found bacteria may be transmitted to humans from contact with flies or surfaces contaminated by flies.

"We may have found one of the primary sources for the spread of some organisms in nature," said Dr. Jerry Butler, the University of Florida (UF) entomologist who led the research. "We confirmed that flies spread bacteria to surfaces, where the pathogens continue to grow. We don’t know yet what the human health implications are, but it reinforces the importance of sanitation and keeping flies out of food establishments."

The study confirms that flies are much more than a nuisance and that they pose potentially serious health risks.

"Flies are a more serious threat to food safety than many people think," Butler said. "People need to consider food safety when they’re eating outside. They need to take a different attitude about a fly crawling across their sandwich."

NINE PATHOGENS DISCOVERED ON FLIES. The UF researches grew cultures from flies collected at the backdoor areas and rear dumpsters of four restaurants in Gainesville, Fla. Within hours, the samples were swarming with nine pathogens. (A complete listing appears on pg. 5.)

Researchers found pathogens that can cause peritonitis, diarrhea, typhoid fever, bacillary dysentery and possibly staph infection. The flies also carried Escherichia coli and Shigella sonnei. The Centers for Disease Control and Prevention (CDC) recently reported that shigellosis was one of the three most common foodborne illnesses diagnosed in 2000. The overall incidence of E. coli O157 infections, which can be derived from Escherichia coli bacteria, increased as well.

Medical research is necessary to determine whether a vector, such as a fly or other pest, might also transmit the disease to humans.

"The study’s findings are significant and the medical research community needs to gather more information to understand its full meaning," said Dr. James Maruniak, a UF microbiologist who led the fly study’s laboratory trials. "It surprised me to find so many bacteria (in the fly samples). I definitely have a different view of flies. There are a lot of potential health implications."

RESULTS PROBABLY TYPICAL. The study’s results, which were confirmed by two independent laboratories, are probably typical of flies across the country, Butler said. House flies migrate up to 10 miles a day. They feed on sugar and organic matter found in foodstuffs, compost piles, garbage and feces. During their short life spans, typically less than a month, flies can spread pathogens across a wide area.

The study’s results do not reflect poorly on the cleanliness of the participating restaurants, Butler said. Garbage was removed from three of the four dumpsters the previous day and the dumpsters had been washed. The flies carried the same pathogens whether they were collected from the clean dumpsters or the one that contained old garbage.

"We need to look more closely at pests as disease transmitters. Orkin is committed to funding research on pests and pathogens to help businesses improve food safety and to reduce the human and economic toll of food-borne diseases," said Frank Meek, technical manager at Orkin.

A white paper on the fly study will be released in December when Butler will present his findings to members of the Entomological Society of America.