UF discovers house flies carrying five new illness-causing bacteria

August 26, 2010 by Mickie Anderson, University of Florida
A house fly perches on a soft drink can in this file photo by University of Florida entomologist Jerry Butler. The tiny white spots are flecks of powdered sugar from an earlier stroll on a jelly doughnut. In a new study, Butler and colleagues tested house flies captured outside restaurants and found they often carried harmful bacteria, including five species never associated with flies before.

Everyone knows that house flies aren't welcome around food. But University of Florida scientists have discovered five new reasons why.

Researchers with UF’s Institute of and Agricultural Sciences have documented five more carried by house flies, and all of them cause illness in humans, ranging from food poisoning to respiratory infections.

In the current issue of Florida Entomologist, the researchers describe collecting house flies near rear entrances and trash bins at four restaurants in Gainesville. About 20 flies from each location were collected in sterile containers and returned to the campus laboratory.

The team used fatty acid analysis and DNA sequencing to identify a total of 11 pathogens carried by the flies - five of them not previously linked to house flies: Acinetobacter baumanni, Bacillus pumilus, Cronobacter sakazakii, Methylobacterium persicinum and Staphylococcus sciuri.

The findings reinforce the notion that fly control is key, especially around food sources, said UF’s Jerry Butler, a retired professor who led the research team.

“People need to know that there’s a reason for health requirements in restaurants,” he said. “Most people have a good immune response, but there are those who are susceptible.” They include infants, seniors and people whose immune systems are compromised by illness or chemotherapy.

Fly control is a day-to-day battle because the insects are so mobile, traveling up to 10 miles in just a couple days’ time, Butler said.

Until this study, house flies were known to carry some 200 bacteria. But both Butler and researcher Jim Maruniak, a UF associate professor of insect pathology, said they expect additional research would turn up even more.

“It just shows you don’t need a lot of flies to contaminate food sources,” Maruniak said.

In addition to the 11 bacteria documented in the study, there were five others that could not be positively identified, researchers said.

House flies’ feeding preferences are particularly troublesome for humans because the insects are attracted to decaying plant and animal matter - materials often found in garbage and animal waste.

“If it smells good to them, we probably want to hide it,” Butler said.

House flies must liquefy food before ingesting it, by placing spongy mouthparts on the food source and secreting saliva or regurgitated gut contents onto it.

The pathogens that can hurt humans are spread by flies through the food-liquefying process, or by defecation.

Pest control company Orkin funded the study. Alejandra Garcia-Maruniak, a UF senior biological scientist, and Frank Meek of Orkin completed the research team.

Meek, the company’s international technical and training director, said his company wanted updated research to stress the importance of fly control in restaurants and kitchens.

“Most people simply wave a fly away and go back to eating, but a cockroach crawling across the table elicits a very different reaction in a restaurant,” Meek said. “However, our research shows that the housefly carries potentially twice as many pathogens as a cockroach. We think it’s important to educate our customers and the public about the health risks pests can pose.”

Explore further: Bugs on Bugs

Related Stories

Bugs on Bugs

August 16, 2007

Bacteria — you can live without ’em, but it won’t do you any good, according to a study of fruit flies by USC College biologists.

Fly Experiment to Fly on Shuttle

June 9, 2006

Fruit flies from UC Davis will join the crew of the space shuttle Discovery on its next mission, set to launch July 1. The flies are part of an experiment on the immune system being conducted by Deborah Kimbrell, associate ...

How the brain decides what to eat

May 13, 2010

Having a balanced diet is a vital concern to all living organisms, not only humans. Animals choose between different food sources according to their nutritional needs. In a study just published in the journal Current Biology, ...

Tiny pest-eating insect fights fruit flies

December 6, 2007

Farmers and vineyard owners have a new weapon in their pest management arsenal. A commonly used parasitoid, or parasitic insect that kills its host, has proven to be quite effective in the control of fruit flies in vineyards. ...

Recommended for you

Loss of a microRNA molecule boosts rice production

October 16, 2018

The wild rice consumed by our Neolithic ancestors was very different from the domesticated rice eaten today. Although it is unclear when humans first started farming rice, the oldest paddy fields—in the lower Yangzi River ...

Big Agriculture eyeing genetic tool for pest control

October 16, 2018

A controversial and unproven gene-editing technology touted as a silver bullet against malaria-bearing mosquitos could wind up being deployed first in commercial agriculture, according to experts and an NGO report published ...

A selfish gene makes mice into migrants

October 16, 2018

House mice carrying a specific selfish supergene move from one population to another much more frequently than their peers. This finding from a University of Zurich study shows for the first time that a gene of this type ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.