Study finds eggs from small flocks more likely to contain Salmonella

Egg_broken-on-white_blogEggs from small local enterprises may not be all they are cracked up to be when compared to “commercially produced” eggs, or those you typically find in grocery stores. This is according to a new study that found eggs from small flocks of chickens are more likely to be contaminated with Salmonella Enteritidis than eggs from larger flocks that are regulated by the U.S. Food and Drug Administration.

This conclusion is based off the first-of-its kind, six-month study done last year by researchers from Penn State University. The researchers collected and tested more than 6,000 eggs from 240 selling points across Pennsylvania, including purchases from randomly selected farmers markets or roadside stands representing small layer flocks.

According to the study, the internal contents of the eggs and egg shells were cultured separately for Salmonella using standard protocols. Salmonella recovered were classified by serotype, and any Salmonella Enteritidis isolates present were further characterized to evaluate their relatedness to isolates of the bacteria that have caused foodborne illness outbreaks.

Test results revealed that of the 240 selling points, eggs from five, or 2%, were positive for Salmonella Enteritidis. Eggs sold at one of the positive selling points contained the bacteria in egg shells; the eggs from the other four selling points had Salmonella Enteritidis in internal contents.

That is a higher prevalence of the pathogen than that found in studies of eggs from large flocks, noted lead researcher Subhashinie Kariyawasam. Those eggs, from flocks of more than 3,000 birds, are subject to federal regulations aimed at reducing Salmonella Enteritidis contamination.

The article explains that these regulations require measures such as placement of Salmonella-“clean” chicks, intensive rodent control, cleaning and disinfecting between flocks, environmental monitoring of pullet and layer houses, continuous testing of eggs from any Salmonella-positive houses, and diverting eggs from Salmonella-positive houses for pasteurization.

“The research highlights the potential risk posed by the consumption of eggs produced by backyard and small layer flocks. And, analysis of the Salmonella Enteritidis present in the eggs from small flocks shows they are the same types commonly reported to the Centers for Disease Control and Prevention from human foodborne outbreaks,” Kariyawasam said in the article. “These findings emphasize the importance of small-producer education on Salmonella enteritidis control measures and perhaps implementation of egg quality-assurance practices to prevent contamination of eggs produced by backyard and other small layer flocks.”

Eggs from small flocks make a negligible contribution to the table egg industry in the U.S., Kariyawasam noted. But the growing demand for backyard eggs and eggs from nonfarm environments — with small egg-producing flocks managed in cage-free systems and pasture situations — suggests these production systems deserve some scrutiny, she added.

“The bottom line is, if you buy your eggs from the small producers, you need to worry about Salmonella just as if you bought eggs produced by large flocks,” Kariyawasam said. “And, beyond the consumption of eggs, birds in these flocks can have Salmonella, so people with backyard poultry need to be aware of the dangers with pet birds.”

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