Ch. 6— Maintaining Animal Diversity Offsite • 147 



gens unique to a given strain of an infec- 

 tious agent to identify circulating antibod- 

 ies. It is rapid and can be highly specific. 

 Continued developments in selection and 

 purification of limited amounts of specific 

 antigens using recombinant DNA technol- 

 ogy may ultimately make ELISA the pre- 

 ferred serologic testing method for most 

 infectious agents. 

 3. Complementary DNA Probes: These probes 

 are derived from cloned DNA or RNA of 

 specific infectious agents and can confirm 

 the existence of the infectious agent in tis- 

 sue samples. The tests would distinguish 

 between animals carrying only antibodies 

 and those that actually carry the infectious 

 agent. The tests would also be of great value 

 in identifying asymptomatic carriers of in- 

 fectious agents that infect circulating white 

 blood cells without eliciting antibody for- 

 mation. 



In addition to movement of entire animals, 

 increased interest in the international transfer 

 of semen and embryos has produced both op- 

 portunities and concerns about disease control. 

 For semen, the risk of disease transmission is 

 usually equated to that associated with the male 

 that produced the semen. When semen is be- 

 ing moved, it undergoes the same tests the 

 donor would undergo if he were being moved. 

 In addition, samples of the semen are usually 

 subjected to various diagnostic tests (44,45). 



The risk via either fresh or frozen embryos 

 is less clear. In many cases, infectious agents 

 are attached to the surface of the embryo or 

 found in the associated uterine fluids. Although 

 standard methods of embryo-washing free the 

 embryo of most such organisms (19), it does not 

 remove all of them (e.g., African swine fever) 

 (11). Research is thus needed on the feasibility 

 of purging embryos of undesirable disease 

 agents. Even if the disease organism cannot be 

 disassociated from the embryo, the contami- 

 nated germplasm may be rendered noninfec- 

 tious by highly specific monoclonal antibod- 

 ies, new antiviral agents, chemical detergents, 

 or immunization of surrogate mothers. 



To date, the suitability of embryos for inter- 

 national movement has been equated to the 



suitability of both parents for such movement. 

 But considerable interest exists in developing 

 procedures that would allow the status of the 

 embryo to be evaluated independently. Such 

 an assessment is likely to become feasible in 

 the future. Indeed, transfer of embryos of wild 

 and domestic animals may ultimately provide 

 the safest means of exchanging germplasm. 



Advances in diagnostic procedures and trans- 

 fer technology should facilitate the interna- 

 tional movement of germplasm. For domestic 

 species and wild ungulates, these developments 

 should make foreign breeds more accessible 

 without increasing the risk of introducing dis- 

 ease. Improved serological testing may allow 

 relaxation of the permanent post-entry quaran- 

 tine now imposed on wild ungulates. For un- 

 regulated species, a mechanism for monitor- 

 ing disease status is needed and should be 

 facilitated by new technologies. These efforts 

 will be particularly important as captive breed- 

 ing programs enlarge, thereby increasing con- 

 tact between exotic and indigenous species. 

 Returning individuals from zoos to the wild will 

 also place a premium on ensuring the health 

 status of released individuals. 



For improved diagnostic and transfer tech- 

 nologies to be most effective, they must be ap- 

 plied both in the United States and in the coun- 

 tries of origin. Currently, USDA-approved 

 quarantine facilities do not exist in Asia and 

 have only recently been developed in Latin 

 America. To set up such facilities and equip 

 them requires capital inputs— costs that are 

 likely to be borne largely by industrial coun- 

 tries. This approach is reasonable in terms of 

 the ultimate benefits that are expected from 

 global maintenance of animal diversity. The 

 costs of importing animals and semen are cur- 

 rently absorbed by the U.S. importer. Yet this 

 approach ignores societal benefits that accrue 

 from access to foreign domestic animal germ- 

 plasm and from maintenance of animal diver- 

 sity as a whole, which argue for a greater U.S. 

 Government role. If widespread maintenance 

 of genetic diversity is the goal, then increased 

 public support for importation, conservation, 

 and use of foreign germplasm is essential. 



