Application of Enzyme Immunoassay in Veterinary Medicine: Serodiagnosis of Bovine Brucellosis

Abstract

Enzyme immunoassay (EIA) techniques have been applied in two principle areas of veterinary medicine; 1) antigen detection for direct demonstration of disease causing agents and 2) antibody detection for indirect or presumptive diagnosis of infection. EIA techniques have been chosen over other primary binding immunoassays (radio- and fluoro-) to replace many of the ‘conventional’ serological assays. EIA techniques offer many advantages; 1) the inherent dangers, waste disposal problems and limited shelf life associated with radioisotopes are not encountered; 2) whereas most fluoroimmunoassay techniques still require subjective or operator judgement, enzymic reactions (chromogenic) may be objectively quantitated with 96 well plate photometers; 3) although 96 well plate fluorimeters are now available, in general photometers are less expensive and far more flexible with respect to the range of chromogens which can be quantitated; 4) the 96 well plate format of EIA techniques has been the major focus for development of computer controlled, automated instrumentation and as a result of these technological advances, accuracy, precision and quality control has been greatly enhanced; 5) electronic data acquisition and processing of EIA results is now well established and supported by commercial or custom microcomputer software, is an important aspect of overall quality assurance in the diagnostic laboratory; 6) EIA techniques in general are faster and less expensive to perform and are technically less demanding than conventional assays such as serum neutralization and complement fixation; 7) EIA techniques, as primary binding assays, are not dependent on antibody specific functions which occur secondarily after binding to antigen (e. g. complement fixation, virus neutralization, bacterial agglutination, precipitation, etc.); 8) the immunological specificity and sensitivity of EIA techniques is adjustable through selection of appropriate antigens and detection reagents; 9) the use of monoclonal detection reagents in EIA techniques has greatly enhanced assay specificity and standardization and 10) the same EIA protocol and test sample may be used for simultaneous detection of antibody to a number of different diagnostic antigens from one or more infectious agents. For the reasons stated above and constant pressures to tailor diagnostic specificity and sensitivity to meet eradication, control and surveillance requirements for infectious diseases, EIA techniques have found wide application in veterinary medicine as applied to both food producing and companion animals. However, it is not our intention to review all of the applications of EIA techniques in veterinary medicine in this chapter, as an extensive bibliography has been recently published (Charan and Gautam, 1984).