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In late September, researchers announced that a man who received a baboon liver in an experimental 1992 transplant contracted a herpes virus known as cytomegalovirus (CMV) from the baboon. The man died of liver failure a couple months after the transplant, but tests of his tissues revealed he was infected with CMV.
Animal rights activists and others opposed to transgenic diseases were quick to pounce on this revelation to argue against animal transplants. But what does this really mean?
First, it is important not to understate the real risk associated with transgenic transplants, especially in the early stages the technology is in. There is simply no way anyone can guarantee that a disease won’t pass from animals to human beings without further research – which, of course, is why this research is still experimental and hospitals around the country aren’t’ doing hundreds of such transplants.
By the same token, it is important not to overstate the risk. Animal-human contact constantly poses risks that most of us find completely acceptable. Few people outside the animal rights community would advocate banning pig farming simply because pigs are an important vector for the influenza virus. Nor would most people advocate eliminating horses because of the handful of deaths from equine encephalitis every year.
It’s also important to note that although the transplant recipient in this case was infected with CMV immediately after the transplant, his body showed no signs of infection at his death. According to an Associated Press story on the case, the reason the virus was able to infect the patient was because he stopped taking the antiviral drug ganciclovir after 18 days because of the side effects. Tissue samples taken 28 days after the transplant show the CMV virus. The patient resumed the ganciclovir, and by day 35 was completely free of the virus. Although no one can be certain, it appears the drug killed the virus.
Even if ganciclovir couldn’t kill CMV, there is a straightforward way to completely avoid this problem – raise animals intended for transplantation in sterile conditions. CMV infects about 98 percent of baboons because it is harmless to the animals; the only way to prevent such infection is to raise the animals in sterile conditions. An AIDS patient who received a bone marrow transplant from a baboon was free of CMV because the baboon used had been raised from birth in a sterile environment, quarantined from other baboons.