Paul Patterson
Professor of Poultry Science
Penn State University

For those readers who have been following the news about eggs and salmonella, here is a very informative Op-Ed article written by Dr. Patterson that was published online in the New York Times on August 25.

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The American food system, and in particular egg producers in Pennsylvania and other states, have made great strides in reducing the risk posed by salmonella enteritidis, to the point where eggs have not been a significant food-safety risk in recent years.

That wasn’t always so. Following a rise in salmonella enteritidis in humans starting around 1970, egg safety became a major concern. In 1990, the U.S. Department of Agriculture traced salmonella enteritidis back to egg farms in the Northeast.

Hens most likely become infected from contaminated environments or from rodents bringing the organism to the birds. While salmonella enteritidis does not typically affect bird health, when a hen has a systemic infection of salmonella, the ovaries, and thus the egg yolks, become contaminated. Contaminated eggs can cause serious illness to people if eggs are not thoroughly cooked.

In response to the increased risk of salmonella, Pennsylvania egg producers, federal and state agriculture departments, Penn State and the University of Pennsylvania in 1992 initiated research to find solutions for salmonella egg contamination. Findings resulted in the establishment of the Pennsylvania Egg Quality Assurance Program, which was the first pre-harvest program in the country based on “hazard analysis of critical control points” to reduce salmonella egg contamination.

In the 18 years since the program began, the percentage of contaminated poultry houses has dropped to 8 percent from 38 percent. In 1992, 26 percent of samples from Pennsylvania hen houses tested positive. Today, that’s down to 1 percent. The risk of exposure from a single egg always was statistically small — just 2.6 per 10,000 eggs from infected flocks tested positive for salmonella in 1992. Today, thanks to the assurance program, that incidence is down more than 50 percent, to 1.2 eggs per 10,000. When Salmonella is found in eggs or poultry houses, eggs are discarded or pasteurized.

The program has been so successful that the Food and Drug Administration in July initiated a national program modeled after it. Had the program been in place earlier, the current outbreak may never have occurred. Now that it is, we can expect to see fewer salmonella outbreaks in American eggs.