WASHINGTON (Reuters) - Bacteria found in chicken feed used at two Iowa farms has been linked to a salmonella outbreak that prompted the recall of more than a half billion contaminated eggs, U.S. regulators said on Thursday.
The U.S. Food and Drug Administration said it would keep investigating to determine whether the bacteria originated in the chicken feed or arrived there from another source.
"We do not know at this point how, when or where this feed may have been contaminated," said Jeff Farrar, U.S. Food and Drug Administration associate commissioner for food protection. "That's part of our ongoing investigation and we'll work very hard to try and determine that."
The contaminated feed was produced at a feed mill that is part of Wright County Egg operation and also went out to the second farm linked to the outbreak, Hillandale Farms of Iowa, FDA said.
The FDA collected around 600 samples from 24 possible sources of contamination on the two Iowa farms, said Sherri McGarry, foodborne outbreak coordinator.
Several Wright County Egg samples tested positive for salmonella, including feed, manure swabs and environmental swabs from a barn.
"The sense that the investigators have is that there's evidence of contamination of the farm. While they have found it in the feed, they are not concluding any type of cause-and-effect relationship," said FDA principal Deputy Commissioner Joshua Sharfstein.
The DNA in Wright County Egg farm samples matched the DNA of the bacteria in the outbreak, but feed ingredients may not have been the originating point for the salmonella outbreak.
"This may well just be that the birds got in and contaminated or there's just contamination in the facility overall," said Joshua Sharfstein, FDA principal deputy commissioner. "So we'll obviously be taking a look at everything, all the pieces of the puzzle as it comes together."
The massive egg recalls came weeks after a new FDA rule took effect that tightened safety rules at large producers and required testing in poultry houses for salmonella bacteria.
The egg rule did not specifically address testing feed for contamination, FDA officials said.
The outbreak, largest since the 1970s, may be linked to almost 2,400 cases of salmonella-related illnesses around the country since May 1, although at least 930 such cases are reported during this time frame on an average year.
The recalled eggs were sold under the brand names Sunny Farms, Hillandale Farms, Sunny Meadow, Wholesome Farms and West Creek, Lucerne, Albertson, Mountain Dairy, Ralph's, Boomsma's, Sunshine, Hillandale, Trafficanda, Farm Fresh, Shoreland, Lund, Dutch Farms, Kemps, James Farms, Glenview, Pacific Coast, Alta Dena Dairy, Driftwood Dairy, Hidden Villa Ranch, Challenge Dairy, and Country Eggs.
(Reporting by Alina Selyukh; Editing by David Gregorio)