TUESDAY, July 23 (HealthDay News) -- An investigation into a bizarre and tragic case of rabies passed from an organ donor to a kidney transplant recipient has revealed more about how the infected organs slipped past safeguards in the donation process.
In March, health officials announced that a Maryland man had died of rabies contracted through exposure to an infected kidney he had received 18 months before he fell ill.
Because it took so long for the patient to develop symptoms, doctors didn't initially suspect his transplant. It was only after ruling out other possibilities and retesting tissue samples saved from the autopsy of the donor that investigators discovered the source of the infection.
They quickly notified three other people who had received organs from the same donor. Those patients have all received protective rabies shots and are doing well, officials said.
Details of the investigation are published in the July 24/31 issue of the Journal of the American Medical Association.
Cases of rabies have been passed through organ transplants before, though health officials say they are extremely rare.
"There have only been three ever-reported clusters of transplant transmitted rabies worldwide, two in the United States and one in Germany, through solid organ transplantation," said Dr. Sridhar Basavaraju, who was part of the team that investigated the deaths.
Basavaraju is an epidemiologist with the Office of Blood, Organ, and Other Tissue Safety at the U.S. Centers for Disease Control and Prevention.
Organ donors are checked for a slew of infectious diseases, including HIV, herpes, hepatitis and cytomegalovirus. They are not routinely screened for rabies. That's partly because the disease is very rare -- an average of two rabies deaths are reported in the United States each year -- and partly because rabies testing can take weeks to return results. Human organs have to be transplanted very quickly, typically within hours of a donor's death.
At the time of his death in 2011, family members of the donor, a 20-year-old man serving in the Air Force in Florida, were asked about possible contact with rabid animals. They were also asked if he'd had rabies shots after recent animal exposures. They answered no to both questions, which are a standard part of the screening process for donations.
The man had died of unexplained encephalitis, or brain swelling. Doctors initially suspected a kind of food poisoning from tainted fish, but tossed that theory after water testing proved it was unlikely. After a thorough autopsy, doctors ultimately blamed his death on severe gastroenteritis, or inflammation of the gut.
They never suspected rabies, though later testing of tissue samples revealed it to be the true cause of his death.
"I think it's important to approach the donor who might have encephalitis a little more broadly and definitely probably consider rabies as a potential cause of it," Basavaraju said.
"When you only see one or two cases of rabies a year in a country of 300 million people, that is a really tough diagnosis to make," he said, adding that the donor's doctors "did an excellent job."
Further interviews with friends and family members revealed that the man, who had moved from North Carolina shortly before his demise, had trapped raccoons and kept them as live bait to train dogs. He'd been bitten by raccoons at least twice. Neither of those animals was known to be sick, however.
Raccoons are the animals most frequently reported to be rabid in the United States, but they rarely infect humans. Only one other case of rabies passed from raccoons to humans has ever been reported in this country, according to study background information.
Because transmission of rabies through organ transplants is so rare and so difficult to detect, experts say this case probably doesn't warrant changes to the organ transplant screening protocols.
In an editorial accompanying the study, Dr. Daniel Kaul, who directs the transplant infectious disease service at the University of Michigan, put the situation in context.
From 2008 through 2011, Kaul noted, more than 113,000 patients received solid organ transplants in the United States. Out of those, 139 people contracted some kind of a disease from their transplanted organ, such as cancer or an infection, and 29 people died as a result. By comparison, nearly 27,000 people died waiting for an organ transplant.
"Anyone involved in organ transplantation realizes that to get to zero in terms of the transmission of infections is not possible," Kaul said.
"That's not in any way to minimize the tragedy associated with cases like this where someone dies when they're getting a lifesaving organ. But we have to be very careful when we try to make new policy that's informed by one case because this is not a common problem," he said, adding, "we would wind up discarding lots of useful organs, and overall, we would do more harm than good."
To learn more about organ transplants, visit the United Network for Organ Sharing.