A disease transmitted to a human after the transplantation of an animal organ.
Xenotransplantation carries the risk of introducing infectious agents from an animal source into the human population as a result of transplantation. This process is termed xenozoonosis. Of particular concern is introducing a new infectious agent into the transplant population that ultimately infects the contacts of transplant recipients, with the potential to cause an epidemic. Evidence of the danger of zoonotic infections can be observed in the Ebola (from monkeys) and Nipah (from pigs) viruses, recent outbreaks of which have been observed in humans.
Although infections such as the Ebola virus lend themselves to rapid detection, diagnosis, and quarantine, many infectious agents that have prolonged periods of quiescence or do not cause clinically evident infection could potentially be transmitted to xenotransplant recipients. Researchers have postulated that retroviruses such as human immunodeficiency virus (HIV) entered the human population after cross-species infection. Of particular concern with respect to the xenotransplantation of pig organs is porcine endogenous retrovirus (PERV), which is permanently integrated into the pig genome. Although PERV has been shown to have the capacity to infect human cells in vitro, a recent study of 160 patients exposed to various living pig tissues did not demonstrate PERV infection.
Graham Bundy, "Xenotransplantation," eMedicine, June 13, 2003
FDA officials warned that many potential risks of cross-species transplants, known as xenotransplants, should be better understood before more patients undergo similar treatments. Some voiced worries about viruses that could pass from animals into humans: "xenozoonoses." They noted that because AIDS patients already have defective immune systems, and because the treatment calls for further immunosuppression to keep the body from rejecting the baboon cells, the risk of bringing new diseases into the human population could be increased.
John Schwartz, "Advisers Back Baboon-Human Cell Transplant," The Washington Post, July 15, 1995
The word zoonosis (zoh.AWN.uh.sis) a disease transmitted from an animal to a human has been in the language since at least 1876. With long established diseases such as rabies and chickenpox, as well as relative newcomers such as Ebola and possibly also HIV and SARS getting slapped with the "zoonosis" label, the term remains common nearly 130 years later.
And now, with the transplanting of animal organs into human bodies known as xenotransplanting (the prefix xeno- means "foreign" or "different") we have something new to fret about: the transmission to the human recipient of a disease that lurks within the animal donor's organ a xenotransplant zoonosis, or a xenozoonosis.