Researchers Study Link between Flies and Salmonella Infection
Microbiologist Peter S. Holt and entomologist Christopher J. Geden, both scientists with ARS, have been studying whether or not flies infected with Salmonella can pass on the Salmonella to chickens.
The first step was studying whether infected hens could infect flies with Salmonella.
“We found that about half the house flies became colonized with Salmonella soon after emergence,” says Holt. The bacteria were detected in and on 45-50 percent of the flies within the first 48 hours, and levels remained at 50 percent or higher for the following 5 days.
The next stage of research involved exposing uninfected hens to the infected flies:
They found that just being around the contaminated flies didn’t cause healthy birds to become infected, but eating infected flies did. And though the studies showed minimal bacterial contamination of the hens’ crops, intestinal colonization occurred in about 38 percent of the birds by days 6 and 13 of the experiment. The crop is a small sack in the digestive system that stores predigested food.
“We found that simple physical contact may not be the primary method of transfer of Salmonella bacteria to different surfaces in a poultry house,” says Holt. “But a hen’s eating of contaminated flies does seem to be the primary mechanism of transmission of Salmonella from flies to birds.”
Holt has shown that flies in poultry houses are not only a nuisance, but also a threat to the safety of poultry products. “Though there is much more to learn about the relationship between Salmonella, flies, and poultry, this research shows that growers need to pay special attention to fly control using methods of surveillance and treatment that are already available,” says Holt.
Quotations and information for this post from "SHOO FLY! Role of House Flies in Spreading Salmonella in Poultry," which was published in the March 2008 issue of Agricultural Research magazine.