public health control measures can only decrease, not eliminate, risk. In the relatively controlled xenotransplant setting where exposure is known to have occurred and where there is prospective monitoring, adequate surveillance may be able to detect new xenogeneic infections in recipients prior to significant spread into the general population. Such early detection would allow suspension of the specific procedure, source animal species, or factors associated with risk, pending the development of adequate methods for prevention and control, thereby reducing the risk of additional infections. However, as noted previously, infectious agents such as HIV, which produce clinical disease only after long latency periods, may spread widely in the population before they are detected.

Summary

To answer the four questions posed at the beginning of this chapter:

  1. Is there a basis for concern regarding xenogeneic infection for individual human recipients? Yes.
  2. Do these concerns constitute a threat to the general public health, rather than being only a complication in the risk–benefit calculation for individual xenogeneic tissue recipients? Although there is considerable debate about the degree of risk, most infectious disease experts agree that some level of risk to the general public health exists.
  3. What options are available for the prevention and control of infectious public health risks associated with xenografting in humans? Preplanned transplantation screening of the animal that is the source of the graft for known zoonotic pathogens and posttransplantation surveillance of the recipient for adverse health events possibly associated with xenogeneic infections are the best tools available.
  4. What approaches are most appropriate for xenotransplantation? A national xenotransplant registry would permit continuing surveillance of recipients for the occurrence of unusual illnesses. Archiving of appropriate biologic specimens from both the animal source and the recipient would be the key to retrospective investigation of the occurrence of such events.


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