Microbiological hazards of xenotransplantation. 2. Facing the risk

The high number of xenotransplantations that have been carried out around the world since the beginning of the century, combined with the quantity of animal experiments that have exposed man to animal viruses under similar conditions, should be measured against the low incidence of known pathological consequences. The pathogenic potential of animal viruses for man, then, is unpredictable; and while the risk is acknowledged, it cannot be defined. Unless no benefit can be in xenotransplantation, the application of the precautionary principle to the extent of a moratorium seems to be excessive. The precautionary principle offers possible modes of action in the face of an unquantifiable risk. In the event of xenotransplantation, precautionary measures should be taken in advance, in order to limit risk to the maximum extent. The risk is reduced and the benefit/risk ratio becomes higher, rendering the challenge acceptable. Preventive measures should be taken as the knowledge grows about possible modes of transmission. Guidelines of good practice should be implemented at each step of the xenotransplantation process: birth of animal source by hysterotomy in a 'Specific Pathogen-Free' (SPF) centre rearing in incubator then in isolated conditions (SPF centre) transportation to and rearing in the procurement site (SPF hospital special wing) surgical procurement and xenotransplantation (hospital) post-surgical reanimation (intensive care unit) convalescence (isolated room--hospital) long-term recipient follow-up (home) All these steps should be taken in such a way as to limit the number of persons coming into contact with the recipient.