KANSAS CITY — Investigators from the Food and Drug Administration have confirmed through testing and DNA fingerprinting that the strain of Salmonella enteritidis that has caused over a thousand illnesses around the United States matches the strain identified at Wright County Egg of Galt, Iowa, and prompted the recall of hundreds of millions of shell eggs. Investigators also have found the same strain in feed from a feed mill at a Wright County Egg farm. What remains unclear is how the feed became contaminated.

“I want to make clear we do not know at this point how, when or where this feed may have been contaminated,” said Jeff Farrar, associate commissioner for food protection in the office of foods at the F.D.A. “Determining the source of the contamination is a part of the ongoing investigation. Obviously, finding a positive in the feed raises a lot of questions.”

Dr. Farrar added that one of the positive samples was from a bone meal ingredient that went into the pullet feed.

“We are digging a little deeper into that,” he said.

On Aug. 13, Wright County Egg initiated a recall of shell eggs due to Salmonella enteritidis contamination. A few days later the company expanded the recall to include approximately 228 million eggs sold under the Lucerne, Albertson, Mountain Dairy, Ralph’s, Boomsma’s, Sunshine, Hillandale, Trafficanda, Farm Fresh, Shoreland, Lund, Dutch Farms and Kemps brand names.

A second recall was initiated by Hillandale Farms of Iowa, North Hampton due to Salmonella enteritidis. The products affected by the second recall are sold under the brand names Hillandale Farms, Sunny Farms, and Sunny Meadow, and were distributed to retail and food service customers in Arkansas, California, Illinois, Indiana, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Texas and Wisconsin.
Since May 2010 the Centers for Disease Control and Prevention, Atlanta, identified a nationwide, four-fold increase in the number of Salmonella enteritidis isolates through PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories.

Christopher Braden, acting director of the division of foodborne, waterborne and environmental diseases at the National Center for Emerging and Zoonotic Infectious Diseases in the C.D.C., said between May 1 and Aug. 25 there were 2,043 illnesses reported associated with the pathogen Salmonella enteritidis. He said the C.D.C. would normally expect to see 933 illnesses caused by the pathogen during that time frame. He added that the current egg recall is the largest outbreak due to Salmonella enteritidis since the agency began keeping such records back in the late 1970s.

The food safety event associated with shell eggs comes at a time when food safety legislation is before Congress. Provisions in the legislation include improving the traceability of foods, prompt access to records and mandatory recall authority. Dr. Farrar said if the legislation was in place it would have helped the F.D.A.’s investigation.

“Had there been an improved traceability system in place it could have sped up the investigation,” he said. “Although the firms were cooperative, mandatory access to records could have helped. As for mandatory recall authority, (the) companies were generally cooperative, but we don’t feel those decisions should rest with the private company.”