Salmonella Slithers Way Into Blood Supply
Blood donor with pet boa constrictor contaminated two recipients
WEDNESDAY, Oct. 2, 2002 (HealthDayNews) -- A 47-year-old Oklahoma man picked up salmonella from his pet boa constrictor, then passed the bug on to at least two other people through blood platelets he donated.
One of those people subsequently died.
The unusual chain of events, chronicled in tomorrow's issue of The New England Journal of Medicine, points up a potential weak spot in the nation's blood supply system, health experts say.
Salmonella is a group of bacteria that can cause diarrhea, fever and abdominal cramps. Although most people recover, about 500 deaths are caused in the United States by the germ each year.
"Salmonella is a big public health problem," says Dr. James George, senior author of the study and professor of medicine at the University of Oklahoma Health Sciences Center.
"Many reptiles live with salmonella as part of the normal intestinal flora, so reptile stools are going to have salmonella. It gets on fingers, and from there it goes everywhere," George explains.
More often, cases of salmonella involve pet turtles, not snakes. However, with an increasing number of reptiles providing a cold form of companionship to humans, doctors are worried that salmonella transmission through the blood supply could be an overlooked hazard.
Up to 3 percent of households now have a pet reptile, and these pets may account for as many as 3 percent to 18 percent of the estimated 12.4 million case of salmonella that occur annually in the United States. By some estimates, 90 percent of reptile fecal matter carries salmonella. You don't have to actually handle the animal to contract salmonella; you just need to live in the same household.
"You track this stuff around a house, and it gets on doors, on curtains, dishes," George says. "This is why hand washing becomes the absolute mantra." Tiny, trace amounts of feces are enough to cause a problem.
Indirect contact is often underemphasized, says Karon Damewood, chief of zoonotic diseases at the Center for Veterinary Public Health at the Maryland Department of Health and Mental Hygiene. Even a trip to the zoo, where a visitor touches a railing that a reptile handler might have touched, is at small risk.
Damewood tells of one 18-month-old infant who contracted salmonella in Baltimore. The family had just moved into a house with new carpeting -- except in one room -- and couldn't for the life of them figure out how the child had become ill. Finally, the parents investigated a spot on the leftover carpet, had it tested, and found it contained salmonella.
"The former owners had scads of reptiles and the pets were not kept in containers," Damewood says.
The platelet donor described in the latest study didn't have symptoms when he donated blood, but it was later discovered that both he and his daughter had been sick with salmonella several weeks earlier.
"We have to assume that at the time he donated the platelets, even though he was asymptomatic and passed all the conditions for being an adequate blood donor, he had to have salmonella circulating in his blood," George says. In fact, the man was a regular donor, having given 50 times at the Oklahoma Blood Institute, including 12 times already that year.
The other factor in this odd tale has to do with how platelets are stored.
Unlike regular blood, platelets are stored at room temperature because low temperatures can change their shape and function. Storage is limited to five days. But even within five days, a single bacterium can generate "10 to the 5th power" more organisms in 27 to 108 hours, the study says.
In this case, the platelets were donated on April 7, 2001. One of the units was transfused into a patient in Tulsa on April 11, and more into another patient in Oklahoma City on April 12.
The first patient, a 51-year-old woman whose leukemia had gone into remission and who was about to be discharged from the hospital, received the unit of platelets just before going home. During the transfusion, she suddenly developed nausea, vomiting, chills and fever.
The second patient, a 50-year-old woman who was in the hospital with severe upper gastrointestinal bleeding and various problems associated with alcoholism and chronic hepatitis C, died of refractory septic shock and hemorrhage the same day she received the transfusion. Although already seriously ill, the woman died from complications from the salmonella contamination, the study says.
Dr. Jean Forsberg, one of the study authors, gets the credit for unraveling the mystery, and unraveling it quickly. As George points out, the second patient could have had chills and fever for any number of reasons. However, Forsberg decided to check the piece of tubing that is routinely retained from all blood transfusions in case a problem arises.
The sample from the tubing was full of salmonella. The doctors then called the other hospital to alert the staff of the possibility of another salmonella infection.
They then traced the platelets back to the donor.
"Even though this is the first report of this sequence, it can't be the first time that it happened," George says.
The issue is a particularly sensitive one for the blood donation industry, which is always short of qualified donors.
"We're not proposing that everyone who has a pet turtle in the neighborhood not donate blood," George says. "But we need to be aware that salmonella is a potential risk in platelet transfusions."
The study suggests routine bacterial cultures of platelet products are feasible. And a technology called Helinx, which sterilizes blood products before they're donated, is in the final stages of development and may provide a remedy.
Most Americans are familiar with salmonella due to contaminated foods. The bulk of tainted foods are often of animal origin, such as beef, poultry, milk or eggs, but all foods, including vegetables, may become contaminated.
"Hand washing is really the key to prevention," she says.
And wash foods, fruits and vegetables as soon as you bring them into the house.
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