Chickens and Eggs
August 26th, 2010The current outbreak of Salmonella food poisoning from contaminated eggs prompts me to share my observations about this fairly common topic, much of which harks back to my days as a CDC epidemiologist.
Salmonella has about 1500 strains, all but one (typhoid fever) native to birds and therefore transmitted via their eggs. The present situation is apparently linked to a large operation in Iowa owned by a fellow with a long record of public health violations. He once paid a $2 million fine but apparently still hasn’t cleaned up his act. The disease is generally mild except in the immunocompromised, including infants and the elderly. Cooking eggs thoroughly kills the bacteria, but sunny-side-up or soft-boiled eggs and even French toast are not guaranteed to be safe. Antibiotic treatment is usually unnecessary and may even prolong the carrier state (remember Typhoid Mary?)
The most common type of food poisoning used to be staphylococcal, the bug that causes most abscesses, boils, etc. Typically a contaminated worker in a bakery would infect a product such as cream puffs or eclairs, which if unrefrigerated for some hours would act as a culture medium, especially in hot weather. Public education and better sanitation among food handlers seems to have made this variety of food poisoning uncommon.
Hepatitis A (“infectious hepatitis”), now controlled by an excellent vaccine, has caused many outbreaks of food poisoning, although the long incubation period (2-6 weeks) makes it hard to detect. A few years ago the L.A. School District had a large outbreak spread by strawberries. For the life of me I can’t understand why the schools still don’t require vaccination when they do require it for hepatitis B and several other diseases. In my CDC days a bizarre epidemic of hepatitis A occurred at a naval base in New Jersey, a “common source” epidemic with a bell-shaped curve of occurrence. What made it odd, and clearly criminal, was that all the cases involved officers and their wives, and eventually some of their children. Turns out a certain career private (he had been demoted several times for insubordination) diagnosed himself with hepatitis based on his jaundice and dark urine, so he urinated into the mayonnaise that went into the potato salad at the Officers’ Mess. The Navy’s punishment was classified. Fortunately everyone recovered.
Another source of hepatitis food poisoning is contaminated shellfish. There’s some rule about not gathering clams, oysters and the like during certain months but some enterprising fellows about the New York – New Jersey waterways were making lots of money breaking the law, digging through the ice in the Raritan Bay to collect these critters. Many folks eat clams and oysters raw or steamed, which it turns out does not kill the hepatitis virus. Researchers at that time also discovered what the ancient Hebrews must have known thousands of years ago; shellfish feed themselves by pumping and concentrating garbage, making them quite adept at transmitting germs.
The investigation which included CDC became rather complicated when it turned out that the Fulton Fish Market was run by the Mob as one of their front operations.
There are other kinds of food poisoning as well. During my two years in Berkeley reports came to us of a huge and dangerous epidemic in the north following an annual gathering of thousands of Sikhs. It was an enormous picnic of sorts, with their traditionally spicy food prepared in large metal cauldrons. We quickly learned that Sikhs do not appreciate Western medicine, do not like government authorities nosing into their business, and carry large knives. We were able to get some information, however, and to treat some of the seriously ill patients. The prolonged cooking as done by them was allowing toxic amounts of heavy metals to leech out of the cookware into the food. This was an unusual example because of the size of the outbreak, but we also learned that many individuals were using old refrigerator shelves to barbecue on, and that toxic amounts of cadmium were being ingested by unwary backyard celebrants. These are historical curiosities nowadays but probably still occur in third-world countries.
With November approaching, there is one other important type of food poisoning worth mentioning. Clostridia are anaerobic bacteria which thrive only in the absence of oxygen, producing well-known diseases such as tetanus, diphtheria, botulism and an important type of diarrhea known as C. difficile which tends to occur in hospitalized patients given high doses of antibiotics. Leftover turkey and to a lesser extent chicken can transmit the toxin from these bugs if cooking temperatures are not high enough to penetrate the entire carcass.
I hope I haven’t spoiled everyone’s appetite!