In a detailed story on Sunday, Columbus Dispatch reporter Alan Johnson previewed one of the flashpoints in the debate over confining laying hens in battery cages. The story provides plenty of evidence that confining hens in small cages is worse for birds and for the people who eat their eggs. But I’ve asked Dr. Michael Greger, our director of public health and animal agriculture, to provide some additional details.
The egg industry has a history of misrepresenting the facts. For example, in the April issue of the trade publication Egg Industry, the chief lobbyist of United Egg Producers declared: "In fact, the Centers for Disease Control have not linked an outbreak of human illness to egg products in almost 40 years. Not a bad record."
Mercy for Animals
Battery-caged hens at Ohio factory farm.
The U.S. Food and Drug Administration, the agency tasked with egg safety, disagrees. The FDA concluded in a 2009 press release: “Egg-associated illness caused by Salmonella is a serious public health problem.” That wasn’t 40 years ago; that was more like 40 weeks ago.
How quickly the egg industry forgets the worst salmonella outbreak in U.S. history—caused by eggs—that sickened an estimated 224,000 Americans in 1994. In 2005, the CDC estimated that infected eggs in a more typical year cause about 182,000 cases of human salmonella poisoning. That’s not an outbreak, that’s an epidemic.
Salmonella is the most commonly diagnosed foodborne bacterial illness in the United States and has been deemed the leading cause of food-related death. Eggs are the leading culprit. Because salmonella can infect the ovaries of hens, eggs from infected birds can be laid prepackaged with the bacteria inside. According to research funded by the American Egg Board, salmonella can survive sunny-side-up, over-easy, and scrambled egg cooking methods. Although thousands die from food poisoning every year in the United States, the vast majority of victims suffer only acute, self-limited illnesses. Salmonella, however, can have life-long consequences, resulting in chronic arthritic joint inflammation and persistent irritable bowel syndrome in children, who are at especially high risk.
One reason millions of salmonella-infected eggs reach American supermarkets every year is the mistreatment of hens by the egg industry. Cramming 100,000 birds or more under a single roof in tiny battery cages creates an immense volume of contaminated airborne fecal dust that can rapidly spread salmonella infection between the birds. The best available science—a study of more than 5,000 egg operations across two dozen countries—found that for every type of salmonella studied and every type of production system examined, there was a significantly lower risk of salmonella infection in cage-free production.
Sixteen scientific studies (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)* have been published in the last five years comparing salmonella risk between cage and cage-free facilities. Without exception they all found that cage operations harbor more salmonella. This then translates out to more human illness. A study published in the American Journal of Epidemiology found that people who ate eggs from caged hens had about twice the odds of coming down with salmonella food poisoning compared to those who did not eat eggs from hens confined in cages.
Last month, the article “Salmonella Thrives in Cage Housing” from the trade publication World Poultry was posted, concluding "the majority of the studies clearly indicate that a cage housing system has an increased risk of being Salmonella-positive in comparison to non-cage housing systems." A study published a few months ago in Poultry Science even found that cage-free hens experimentally infected with salmonella may clear the infection faster than caged hens.
Like the tobacco industry before it, though, the overwhelming scientific evidence doesn't keep the egg industry from falsely claiming that caging hens is better for food safety. California voters didn't buy it, and voted to ban the practice of caging hens in 2008 by a landslide. In a moment of rare candor, the editor of the industry trade journal Egg Industry admitted after the election that industry claims of food safety risks were "invalid…unsupportable and easily refuted."
In the upcoming battle in Ohio you can be assured that both opposing campaigns will have scientists on their side, but only one will have science on its side.
*Editor's Note: Links to 10 more studies (7-16) have been added.