This article from The Atlantic is really an eye-opener. It lays out the case that the huge "egg factories" housing millions of caged hens which never see the light of day, surrounded by manure, rodents and flies may well be the breeding ground for these diseases.
. . . June
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Where the Salmonella Really Came From
Food - The Atlantic:Sep 8 2010, 9:09 AM ET
It's been nearly one month since the nationwide recall of 550 million eggs, and the Food and Drug Administration (FDA) still hasn't figured out where the salmonella that sickened 1,470 people originated.
Well, I know where it originated, and I am about to reveal it here, both to save the FDA further trouble and to warn the public that the food safety bill currently before the Senate (which may be fast-tracked as election-wary lawmakers return from their break) might not prevent future food contamination epidemics. In fact, it could even cause serious harm to conscientious farmers whose meat, poultry, and produce has never sickened anybody.
Put simply, the cause of the current salmonella outbreak is industrial-scale factory farming, which has also been the cause of virtually every instance of bacterial food contamination the country has experienced in recent years. Huge farms and processors that ship their products across the nation have given us E. coli in ground beef and spinach, Salmonella in peanut butter and fresh salsa, and Listeria in processed chicken. Scanning this list of food-borne illness outbreaks in the United States in the last 15 years, I can find only one instance, Listeria-tainted milk from Whitter Farms in Massachusetts, where a small, local operation sickened its customers.
FDA officials who examined the farms behind the current rash of egg-induced sicknesses were shocked to discover evidence of manure—along with rodents, flies, cats, and birds—in the facilities, which housed 7.7 million caged hens. I, too, maintain a flock of laying hens, although mine is only a dozen strong. My chickens sleep in an abandoned horse stable and spend their days running loose, pecking and scratching around the property. They are no strangers to manure, flies, cats, birds, and the occasional rodent. But my eggs have never sickened anyone. Hens have been living in proximity to insects, mice, and other wildlife for millennia. What is new are the huge facilities containing millions of caged birds that never see the light of day.
Read on . . .