How Did Salmonella Contaminate So Many Eggs?

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Salmonella can infect the eggs we buy in two basic ways:

  1. Hens with infected ovaries or oviduct tissue contaminate eggs before they’re laid.
  2. The bacterium can penetrate the shell when a laid egg is exposed to fecal material.

“We used to think that just washing the eggshell, and using Grade A shell eggs, would keep us safe,” says Patrick McDonough, PhD, a professor of microbiology and clinical bacteriologist at the Cornell College of Veterinary Medicine. “However, we know that infected hens do not show clinical signs and that the infection is harbored in the ovaries. When the shell is laid down, it actually covers the yolk, the albumen [egg white] and the infection.”


In July, the U.S. Food and Drug Administration enacted new egg safety requirements for producers with 50,000 or more laying hens (about 80% of our egg supply). The rules, which the FDA estimated would reduce egg-related salmonella infections by nearly 60%, mandate:

  • Buying chicks and young hens only from suppliers that monitor for salmonella bacteria
  • Establishing rodent and pest control, as well as biosecurity measures, to prevent the spread of bacteria throughout the farm by people and equipment
  • Conducting testing in the poultry house for salmonella enteritidis, with specific measures for handling infected eggs
  • Cleaning and disinfecting poultry houses that have tested positive for salmonella enteritidis
  • Refrigerating eggs at 45°F during storage and transportation, no later than 36 hours after the eggs are laid

Many experts say proper precautions could have prevented the Wright County Egg recall, and the New York Times reports that company owner Jack DeCoster “has had run-ins with regulators over poor or unsafe working conditions, environmental violations, the harassment of workers and the hiring of illegal immigrants.”

Per the Times, DeCoster previously paid a $2 million fine to the Occupational Safety and Health Administration. And Robert Reich, President Clinton’s Secretary of Labor, called DeCoster’s workplace “an agricultural sweatshop.”

“If all works as it is supposed to, we would not have salmonella enteritidis outbreaks,” Dr. McDonough says. “Because we know the risks and how to control, prevent or mitigate as appropriate, the number of outbreaks should be able to be decreased. This is especially important, as we have a growing aging population, and these people are one of the groups especially at risk.”

In the meantime, going organic can help protect you from the dangers posed by factory farms.

Photos: Farm Sanctuary

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