Which came first—the salmonella or the egg?

The Copper Pot With Eggs and Fruitby Ellen Buselli


The Incredible Edible Unsafe Egg?

It’s hardly surprising these days when news breaks that yet another food has sickened people across the country. A few months ago it was eggs. More than 1,600 cases of Salmonella enteritidis infection from eggs were reported in at least 10 states—the largest outbreak of this type of food poisoning ever recorded in the U.S. More than a half billion eggs were recalled. Here’s a look at what went wrong at the henhouse—and what you need to know to eat eggs safely.

Which came first—the salmonella or the egg?

The source of the outbreak was traced to two industrial farms in Iowa, where the barns were infested with rodents, flies, and maggots, and filled with tons of manure, all of which can harbor or spread salmonella. Salmonella was detected in the feed given to young hens, in the water used to wash the eggs, and elsewhere. One of the companies had already been cited numerous times over the years for unsanitary conditions and salmonella contamination.

But how does salmonella end up inside an egg? When salmonella is in the environment (including feed), the bacteria can get inside the chicken. This doesn’t sicken the bird, but if salmonella is in the ovaries or oviduct, the hen can pass the bacteria into her eggs before the shells form. And if the eggs aren’t properly cooled, the bacteria multiply quickly. Eggs can be contaminated from the outside, too, since the shells have tiny pores through which salmonella can penetrate. Thus, if the processing plant equipment is contaminated, or if workers have salmonella on their hands, eggs can end up with the bacteria.

Caged vs. cage-free

Like other factory farms, those involved in the outbreak housed tens of thousands of chickens in small stacked cages. Though not proven, it appears that keeping huge numbers of chickens in enclosed spaces increases the risk of infection more than “cage-free” or pasture-based operations do. If the barns are not cleaned well (many are not), the chickens are exposed to a continual stream of bacteria-laden droppings. Infections can spread quickly. The European Union will ban the practice of using small cages in 2012; California will prohibit it in 2015. But any dirty farm, whether it cages its birds or not, is susceptible to contamination. What’s really key is keeping facilities clean. Don’t assume that organic eggs are necessarily safer, either. Research from the USDA has, in fact, found salmonella in certified organic chickens, as well as in those labeled “free-range” and “all-natural.”

Looking forward

The FDA already had new safety rules in place for large egg producers in early July, but it was too late to prevent the summer outbreak. The rules, which will expand to smaller egg farms in 2012, cover areas such as the control of rodents, clean water, proper refrigeration of eggs, and testing of henhouses for infection; facilities will be inspected for compliance. There are also vaccines that reduce salmonella infection in laying hens, though the FDA does not require them, citing inconclusive evidence of their effectiveness in real-life conditions. The agency is reviewing the issue again. In the meantime, many farmers already inoculate their hens.

Shelling out safety advice

The risk of salmonella in eggs is small in the U.S.—by some estimates, only 1 or 2 out of 20,000 eggs harbor the bacteria—and should lessen even more as the new FDA rules take hold. But you should always treat every egg as if it were infected. One bad egg can cause illness, with symptoms of fever, cramps, diarrhea, nausea, and vomiting. Pregnant women, infants, young children, the elderly, and people with compromised immunity or a chronic debilitating condition are more likely to become sick and develop serious, even life-threatening, complications.

Egg-cellent tips:

• Don’t buy eggs that are cracked or dirty, past their “sell-by” or expiration dates, or unrefrigerated.

• Promptly refrigerate eggs at home, in their carton; don’t put them in the door. The refrigerator should be 40°F (4°C) or below.

• Cook eggs thoroughly—that means not eating eggs with runny or undercooked yolks. Cook casseroles and other dishes containing eggs to 160°F (72°C). Don’t eat—or let kids eat—raw cookie dough or cake batter if they contain eggs.

• Don’t keep cooked eggs or egg dishes at room temperature longer than two hours.

• Discard raw eggs after three to five weeks; hardboiled eggs after one week; and cooked egg dishes after three or four days.

• Wash your hands well after handling raw eggs, as well as all surfaces in the kitchen that come in contact with raw eggs.

• Be wary of foods that may contain raw eggs, such as Caesar salad dressing, hollandaise sauce, homemade mayonnaise, and fresh eggnog. Some restaurants use pasteurized eggs, which makes them safe—ask. You can also buy pasteurized whole eggs or pasteurized egg products (more widely available) to use in recipes that call for raw or undercooked eggs. They cost more but are safe because the heat process kills salmonella and other microorganisms, both inside and outside the egg.

UC Berkeley Wellness Letter, January 2011



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