An extremely rare infection has been passed from an organ donor to at least one recipient in what is thought to be the first human-to-human transfer of the amoeba, medical officials said Friday.
Four people in three states received organs from a patient who died at the University of Mississippi Medical Center in November after suffering from neurological problems, said Dave Daigle, a spokesman for the Centers for Disease Controls and Prevention.
Organs are routinely tested for HIV, hepatitis and other more common infections, but occasionally rare ones slip through.
"We test for the known harmful diseases, but there's not a test for every single pathogen out there," said Dr. Kenneth Kokko, medical director of kidney transplants at UMMC.
Two of the recipients are critically ill, but the others haven't shown symptoms, Daigle said. The CDC confirmed the presence of the organism, known as Balamuthia mandrillaris, in one of the recipients.
Dr. Shirley Schlessinger, a UMMC doctor and medical director of the Mississippi Organ Recovery Agency, would not say which states had patients receiving the organs.
The public should not be concerned, both Schlessinger and Daigle said.
Balamuthia mandrillaris is a microscopic parasite found in soil that causes encephalitis in humans, horses, dogs, sheep and nonhuman primates. Scientists think people get infected by breathing it in, but it can also pass into the blood through a cut or break in the skin. It can be especially dangerous to people undergoing organ transplants, whose immune systems are purposely weakened so their bodies don't reject their new organs.
Human infections are very rare: Only about 150 cases have been reported worldwide since the disease was first identified in 1990. But it can be hard to diagnose because few laboratories test for it and many doctors don't know about it. Some cases are not identified until autopsy, according to the CDC.
"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," she said. "It's very rare so the likelihood that this will happen again (is small), I mean, it's rarer than rabies."
There are risks to transplants and doctors can't test for everything, but the potential benefits far outweigh the risks, she said.
AP Medical Writer Mike Stobbe in Atlanta contributed to this report.
On the Net:
CDC details on Balamuthia mandrillaris: http://bit.ly/7swHMV
University of Mississippi Medical Center: http://www.umc.edu/