Cases in which salmonella was detected at egg facilities have plummeted from about one quarter of tests in 2010 — the year of a national salmonella outbreak linked to eggs — to 2.5 percent in 2015.
This is according to Iowa State University’s Veterinary Diagnostic Laboratory, which each year tests nearly 13,000 environmental samples from egg facilities in Iowa and 14 other states.
Federal and state inspections of egg facilities were suspended in May when a bird flu outbreak hit Iowa and other states. More than 30 million Iowa laying hens and turkeys were killed as producers culled their flocks to stop the disease. It cost producers more than $1 billion.
Officials halted poultry farm inspections because of fears inspectors could carry the disease from farm to farm, said Dustin Vande Hoef, spokesman for the Iowa Department of Agriculture and Land Stewardship. Critics say it may jeopardize the safety of eggs produced in Iowa — the largest egg-producing state in the nation with 43.8 million laying hens.
Although poultry site visits are on hiatus, testing of samples from poultry houses of more than 3,000 laying hens — about 98 percent of operations nationwide — has been ongoing since 2010, when it was required as part of the U.S. Food and Drug Administration’s Egg Rule, said Yuko Sato, ISU assistant professor of poultry diagnostics and production medicine.
“Over the past year, egg safety testing has been continuous and ongoing,” Sato said. “Environmental sampling and testing continued throughout Iowa’s avian influenza crisis and its aftermath.”
Environmental samples, which can be from egg conveyor belts, the ground or chicken manure, are sent to labs like ISU’s. When one of these tests turns up positive, the FDA requires testing of egg shells, which involves four tests of 1,000 eggs each.
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Of 175 positive environmental tests from 2010 to 2015, only one showed salmonella at the eggshell level, which occurred during a 2010 recall of 550 million eggs nationwide, ISU reported.
Egg producers with fewer than 3,000 laying hens aren’t required to provide environmental samples, but some do, Sato said. In 2012, there were 3,707 Iowa operations with fewer than 3,200 layers, but those operations accounted for only .27 percent of the total Iowa flock, said Hongwei Xin, director of ISU’s Egg Industry Center.
Part of the reason for declining positive salmonella tests could be more producers vaccinating their birds against salmonella, Sato said.
The FDA’s 2010 Egg Rule also forced producers with 50,000 laying hens or more to use refrigeration during egg storage and transportation. Producers were also required to adopt pest control strategies and disinfect poultry houses after a positive salmonella test.
Former Iowa egg barons Jack DeCoster and son Peter DeCoster were sentenced in April 2015 to three months in prison after being linked to the 2010 salmonella outbreak that sickened thousands. The DeCoster’s now-defunct company, Quality Egg LLC, was ordered to pay nearly $6.8 million.
Salmonella causes diarrhea, fever and abdominal cramps that usually last just a few days. But the illness is linked to 19,000 hospitalizations and 380 deaths a year, Atlanta-based Centers for Disease Control and Prevention reported.