Flies and Salmonella: dangerous duo in poultry houses
Flies may be more than a mere nuisance in poultry
houses. They may also spread food poisoning bacteria such as Salmonella
enteritidis to chickens and their eggs, the USDA ARS
The common housefly, Musca domestica, readily picks up bacteria from its
surroundings, says Agricultural Research Service (ARS) microbiologist Peter S. Holt
* and entomologist Christopher J. Geden
**. When the chickens eat the flies, the
bacteria get inside the birds.
In three experiments, Holt placed chickens in individual, adjacent laying
cages. Geden delivered fly pupae just 48 hours short of hatching as flies; this
timing ensures the flies aren't exposed to any microbe prior to emergence. The
fly pupae were placed in an open box in the bird room. Three days later, hens
were orally infected with Salmonella.
The researchers detected the bacteria in and on 45-50% of the flies within
the first 48 hours of the flies' hatching.
Uninfected hens were then exposed to the newly infected flies. Just being
around the flies didn't cause healthy birds to become infected, but eating
infected flies did. This showed that simple physical contact may not be the
primary method of transfer of Salmonella bacteria to different surfaces in a
poultry house. But, according to the researchers, a hen's eating of contaminated
flies does seem to be the primary mechanism of transmission of Salmonella from
flies to birds.
According to Holt, this shows that flies in poultry houses are not only a
nuisance, but also a threat to the safety of poultry products.
* Holt works in the Egg Safety and Quality Research Unit at the ARS
Richard B. Russell Research Center in Athens, Ga.
** Geden is at the ARS Center for Medical, Agricultural and Veterinary
Entomology in Gainesville, Fla.
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