December 19, 2009

Rare Organism Passed On To Transplant Recipients

In what is believed to be the first human-to-human transfer of an amoeba organism, an exceptionally rare infection has been passed from an organ donor in Mississippi to at least one transplant recipient, officials with the Centers for Disease Controls and Prevention reported Friday.

CDC spokesman Dave Daigle said four people in three states had received organs from a patient who died at the University of Mississippi Medical Center in November after suffering with neurological problems.

Two of the transplant recipients are critically ill, while the others have not shown symptoms, Daigle said.  The agency confirmed the presence of the organism, known as Balamuthia mandrillaris, in one of the recipients.  

Although organs are commonly tested for hepatitis, HIV and other frequently occurring infections, rare ones can occasionally slip through.

"We test for the known harmful diseases, but there's not a test for every single pathogen out there," the AP quoted Dr. Kenneth Kokko, medical director of kidney transplants at UMMC, as saying.

Both Daigle and Dr. Shirley Schlessinger, a UMMC doctor and medical director of the Mississippi Organ Recovery Agency, told the AP that there was no need for public concern about the infections. 

Schlessinger would not say which states had patients that had received the organs.

Balamuthia mandrillaris is a tiny parasite found in soil that causes encephalitis in humans, dogs, sheep, horses and nonhuman primates.

Scientists believe humans become infected by inhaling the microscopic organism, but it can also pass into the blood through a cut or break in the skin.

Infections can be particularly dangerous to transplant recipients, whose immune systems are intentionally weakened so their bodies won't reject their new organs.

Human infections with Balamuthia mandrillaris are extremely rare, with just 150 cases having been reported worldwide since the disease was first identified in 1990.

Infections can be difficult for doctors to diagnose because so few laboratories test for Balamuthia mandrillaris.  Indeed, some doctors are not even aware of the organism, and in some cases infections are not identified until autopsy, the CDC said.

"The thing we don't want to happen is for people to take this rare and extraordinary anomaly and think it speaks to a lack of safety," Dr. Schlessinger said.

"It's very rare so the likelihood that this will happen again (is small), I mean, it's rarer than rabies."

Despite the fact that doctors can't test for everything, the potential benefits of organ transplants far outweigh the risks, she said.


Image Caption:  Trophozoites of B. mandrillaris in culture. CDC


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