U. FLORIDA (US)—Researchers have documented five bacteria species carried by house flies that cause illness in humans, ranging from food poisoning to respiratory infections.

In the current issue of Florida Entomologist, the researchers from the University of Florida 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, says Jerry Butler, a retired entomology professor who led the research team.

“People need to know that there’s a reason for health requirements in restaurants,” he adds. “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 says.

Until this study, house flies were known to carry some 200 bacteria. But both Butler and researcher Jim Maruniak, an associate professor of insect pathology, says 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 says.

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

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 says.

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.

More news from the University of Florida: http://news.ifas.ufl.edu