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.