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All Eggs Are Not Created Equal

A new study shows that eggs from small flocks are more likely to contain Salmonella.

Eggs from small flocks of chickens are more likely to be contaminated with Salmonella enteritidis than eggs sold in grocery stores, which typically come from larger flocks that are regulated by the U.S. Food and Drug Administration, according to researchers in the college.

That conclusion--which flies in the face of conventional wisdom that eggs from backyard poultry and small local enterprises are safer to eat than "commercially produced" eggs--was drawn from a first-of-its kind, six-month study done last year in Pennsylvania. Researchers collected and tested more than 6,000 eggs from 240 randomly selected farmers markets or roadside stands representing small layer flocks in 67 counties of Pennsylvania.

Test results revealed that of the 240 selling points included in the study, eggs from five--2 percent--were positive for Salmonella enteritidis , which is a higher prevalence of the pathogen than that found in studies of eggs from large flocks.

Lead researcher Subhashinie Kariyawasam, microbiology section head in the Animal Diagnostic Laboratory, presented the findings to the American Veterinary Medical Association and the American Association of Avian Pathologists at their August meeting in San Antonio, Texas.

"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," said Kariyawasam. "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. 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."

Salmonella enteritidis is a leading foodborne pathogen in the United States, with many outbreaks in humans traced back to shell eggs. The FDA requires shell-egg producers from farms with more than 3,000 chickens to be in compliance with the FDA Final Egg Rule, which is aimed at restricting the growth of pathogens. However, small flocks with fewer than 3,000 layer chickens currently are exempt. Eggs from these producers often are marketed via direct retail to restaurants, health-food stores, and farmers markets, or sold at on-farm roadside stands. Like other foodborne bacteria, Salmonella enteritidis is destroyed by proper cooking. However, Salmonella infections can be very serious, even life-threatening, especially, to the very young, the elderly, and people with weakened immune systems.

--Jeff Mulhollem