146 • Technologies To Maintain Biological Diversity 



diversity within captive populations will re- 

 quire the international transfer of animals for 

 breeding purposes. And third, the optimum use 

 of domestic animal germplasm for food pro- 

 duction depends on the international move- 

 ment of desirable breeds and strains to coun- 

 tries where they may be useful. 



International transport of animal germplasm 

 is accompanied, however, by the risk of intro- 

 ducing and spreading disease agents and vec- 

 tors, many of which could have an enormous 

 impact on animal productivity. Indeed, trans- 

 porting animal germplasm without appropri- 

 ate safeguards could jeopardize the conserva- 

 tion programs for which the germplasm is 

 required. Thus, technologies to facilitate germ- 

 plasm transfer must also limit the risk of dis- 

 ease transmission. 



Many infectious diseases are caused by 

 organisms that do not naturally occur in the 

 United States, and their introduction could 

 have serious effects on U.S. animals. Those 

 causing most concern are foot-and-mouth dis- 

 ease, African swine fever, rinderpest, foreign 

 bluetongue strains, scrapie, fowl plague, velo- 

 genic viscerotropic Newcastle disease, and 

 Venezuelan equine encephalomyelitis (20). Cur- 

 rent programs to exclude entry of pathogenic 

 organisms vary with the species, disease, and 

 country of origin. 



For most wild species (including nonungu- 

 late mammals, most birds, reptiles, amphibians, 

 and most fish), regulatory controls to prevent 

 introduction and transfer of hazardous diseases 

 are virtually nonexistent. Except for inspection 

 at the time of entry, movement of such indi- 

 viduals is not restricted. In contrast, entry re- 

 quirements for domesticated livestock species 

 are quite stringent, especially for those com- 

 ing from countries that harbor foot-and-mouth 

 disease, rinderpest, scrapie, or velogenic 

 viscerotropic Newcastle disease. 



All imported domestic animals are subjected 

 to a variety of diagnostic tests and to varying 

 periods of quarantine in both the country of 

 origin and the United States. Greater control 

 reflects the wide potential dissemination of 

 these animals throughout the livestock indus- 

 try. Wild ungulates (hoofed mammals) can carry 



diseases transmissible to livestock and have 

 importation requirements similar to those of 

 domesticated livestock, but also must remain 

 in permanent post-entry quarantine in U.S. De- 

 partment of Agriculture (USDA)-approved fa- 

 cilities. They can be moved from one USDA- 

 approved zoo to another, however, and their 

 offspring can be transferred to nonregulated 

 facilities. 



Current efforts to control introduction of for- 

 eign diseases center on combined strategies of 

 blood (serological) testing and quarantine. Some 

 tests are designed to detect antibodies to spe- 

 cific disease organisms and can thereby iden- 

 tify individuals that have been exposed to the 

 disease at some time; other tests may be used 

 to detect the presence of a specific pathogen. 

 Periods of quarantine support these procedures 

 by allowing an incubation period for animals 

 that may have been infected recently. The tests 

 are conservative, because individuals that have 

 been exposed to a disease but no longer retain 

 the organism still carry antibodies and react 

 positively. However, the procedures also facili- 

 tate identification of asymptomatic carriers of 

 the various diseases. 



Some serological procedures, such as the 

 complement fixation and the viral neutraliza- 

 tion tests, are at times unable to adequately dis- 

 criminate between pathogenic and nonpatho- 

 genic organisms. These limitations have made 

 it very difficult to obtain negative test results 

 for some diseases. Recent advances in diagnos- 

 tic procedures have yielded tests with much 

 greater accuracy and specificity. Three of the 

 most important are the following: 



1. Indirect Immunofluorescence: This proce- 

 dure can provide very rapid screening of 

 samples for a variety of infectious agents. 

 Although it lacks specificity for some dis- 

 eases, it greatly facilitates the initial screen- 

 ing process. 



2. Enzyme-Linked Immunosorbent Assay 

 (ELISA): The compounds that are pro- 

 duced by a disease organism and that elicit 

 the production of antibodies by the infected 

 individual are called antigens. This test 

 uses carefully selected and purified anti- 



