"Striking increases" in illnesses caused by a particular strain of salmonella, once concentrated in the Northeastern United States, are spreading to other regions, according to federal health officials.
Although a variety of meat items are known sources of Salmonella enteritidis, a disproportionate number of the recent outbreaks have occurred after people consumed raw or undercooked eggs.
Illnesses caused by this bacteria continue to be clustered in the New England and Mid-Atlantic regions of the country. However, the Centers for Disease Control in Atlanta have also detected an increasing number of cases in the Mountain and Pacific states.
While recommending that consumers thoroughly heat eggs in order to destroy any pathogen that may be present, the federal government has also formed an interagency task force to deal with the problem.
Representatives from the U.S. Department of Agriculture and the U.S. Food and Drug Administration are urging state health departments to test local chicken flocks for S. enteritidis.
The laboratory testing, a voluntary program at present, is designed to identify those birds acting as the bacteria's source. Under the plan, producers faced with infected hens can have the flock's eggs diverted into pasteurization, a heat process that destroys the organisms. Thus treated, the eggs may then be used for commercial food products.
However, flocks that test positive for S. enteritidis must eventually be destroyed in order to eliminate the problem, according to government representatives. To date, as many as 1 million infected birds have been killed, virtually all of them from a single poultry farm in Maryland.
Even so, an industry representative strongly emphasized that eggs are just one of a number of potential sources for the bacteria.
"Once you start blaming one product or food item for the outbreak of a particular type of food poisoning, then the more likely that product is to get blamed for other outbreaks," said Cathy McCharen, vice president of the Egg Nutrition Center in Washington. "For most public health investigations there is never a clear indication of the cause (of illness)."
Nevertheless, McCharen said that her organization and also the United Egg Producers and the American Egg Board are in favor of the testing program.
"There is a good indication that there is a relationship between eggs and S. enteritidis. We are very supportive in terms of finding the problem flocks, and this testing program will do that," she said. "We want to find and get rid of the problem."
Federal officials, though, are convinced of the link between eggs and the bacteria.
For instance, the CDC studied 19 outbreaks of S. enteritidis . Of the outbreaks surveyed, 15, or 79%, were associated with Grade A eggs or with food from those eggs, according to Chris Lecos, an FDA spokesman.
"This came out of nowhere," said Lisa Lee, VMD, a CDC epidemiologist. "We are focusing on eggs, and we have isolated (the salmonella bacteria) from eggs. . . . It's a fairly serious issue."
Only a fraction of the commercial supply--60 billion eggs annually--is thought to be contaminated with the bacteria, which can cause nausea, vomiting, diarrhea and fever. However, the pathogen can be fatal for some high-risk groups such as infants, the elderly, pregnant women and those with weakened immune systems, such as cancer or AIDS patients,
Since medical investigators have become aware of the problem there have been 14 deaths linked to S. enteritidis transmitted via undercooked eggs, according to Thomas Schwarz of the FDA's retail food protection branch.
Most of the victims were residents of nursing homes and had other serious illnesses, Schwarz said.
The CDC reported earlier this year that there were 6,390 cases of S. enterididis in 1987, making it the second most common form of salmonellosis. The number of reported cases, however, comprises only between 1% and 10% of the actual number of such illnesses in the nation, according to epidemiologists, who study the origins of disease.
Previously, S. enteritidis was thought to constitute about 10% of all salmonellosis cases reported to the CDC. In 1987, though, that figure rose to 16% of the total cases.
Hardest hit are the Mid-Atlantic states, where 36% of all salmonellosis cases were S. enteritidis , well above the national average . And in New England this particular strain comprised 26% of the illnesses in this disease category. In the Western United States, S. enteritidis constitutes about 7% of the salmonellosis cases; in the Mountain states it is 9%.
The pervasiveness of the pathogen has surprised representatives of the federal agencies studying the problem. Apparently, researchers believe that egg yolks are being infected in hens' ovaries even before a shell is formed.
"Finding that intact, uncracked eggs are apparently infected in the chicken was quite a surprise to us," said Dr. Paul Blake, an epidemiologist with CDC.
In addition to recommending that consumers cook eggs fully in order to rid them of any bacteria that may be present, the USDA has also cautioned institutional food-service operations against preparing recipes that call for raw eggs, such as Caesar salad, eggnog, Hollandaise sauce or mayonnaise.
"People need to realize that if you have a high risk of infection--such as those on certain antibiotics or cancer patients--then all raw animal products, including seafood, raw eggs, meats, etc., should be avoided," said McCharen.