The safety of eggs making their way into grocery stores and consumers’ homes has increased dramatically over the past six years, according to testing by Iowa State University (ISU).
The number of egg facility environmental samples testing positive for the salmonella enteritidis bacterium that causes food poisoning declined from 24.5 percent in 2010 to 2.5 percent in 2015, according to ISU’s Veterinary Diagnostic Laboratory.
"The test data also show that the likelihood of a positive environmental test translating into contaminated eggs is extremely low," said Hongwei Xin, director of the Egg Industry Center at Iowa State. "It’s a very positive outcome of the industry implementing the federal egg safety rules that went into effect in July 2010."
Although egg facility inspections were suspended last year due to the avian flu crisis that killed more than 30 million chickens and turkeys in Iowa, officials say the salmonella testing has remained in place.
"Over the past year, egg safety testing has been continuous and ongoing," said Dr. Yuko Sato, assistant professor and extension poultry veterinarian at Iowa State.
The ISU lab annually conducts tests on nearly 13,000 environmental samples. About 60 percent of the samples originate from Iowa egg farms and the remainder from sites located in more than a dozen other states.
The U.S. Food and Drug Administration (FDA) requires facilities housing more than 3,000 laying hens, comprising more than 98 percent of the nation’s flocks, to take environmental samples during various stages of production. Environmental samples are taken from the surfaces of egg conveyor belts, floors and poultry manure to check for the presence of salmonella. Samples are submitted to the ISU lab to be tested for the salmonella bacterium.
Potential reasons for the significant drop in positive samples may include an increase in flocks that are vaccinated for the salmonella bacterium, according to Xin.The supply of vaccine since 2010 has jumped dramatically, with the number of doses produced reaching over 200 million in some years, more than four times the amount produced in 2010.
There also has been heightened awareness and training in salmonella enteritidis prevention, he added.
When an environmental sample does test positive, further measures are taken to ensure consumer safety. In those situations, the FDA requires four consecutive tests of 1,000 shell eggs from the affected facility at specified intervals, which are separated into egg pools consisting of the contents and shells of 20 eggs.
The ISU Veterinary Diagnostic Laboratory tested more than 35,000 egg pools from 2010 to 2015 under the FDA protocols. During that time period, only one positive egg pool was identified, which occurred during the timeframe of a 2010 national egg recall.
"The FDA’s Egg Safety Rule requires the farms to test and then to act on those tests if there is the possibility of contamination," Sato said. "From the test results we are seeing, the rules are functioning as they were meant to — to ensure egg safety."
While continued efforts are being made to ensure egg safety in the supply chain, consumers also must continue to be vigilant in how they obtain, handle, store and prepare eggs to reduce the potential for contamination, said Xin.