SELECTION OF EUROPEAN UNION STANDARD REFERENCE SERA FOR USE IN THE SEROLOGICAL DIAGNOSIS OF INFECTIOUS BOVINE-RHINOTRACHEITIS

A study, consisting of three trials, was undertaken in order to find s tandard reference sera for use in serological diagnostic procedures fo r infectious bovine rhinotracheitis (IBR) in the European Union (EU). A total of forty-nine laboratories participated in the trials, in whic h panels of positive, weak positive, and negative candidate sera were tested blind by neutralisation, indirect and blocking enzyme-linked im munosorbent assay, indirect immunofluorescence and passive haemaggluti nation. A serum which scored positive in all tests in all laboratories was selected as a strong positive standard serum. The chosen negative standard serum gave negative results in virtually all tests. A 1/36 d ilution of a positive serum was chosen as the weak positive standard s erum and only very sensitive techniques were able to score it positive . Three EU reference sera are now available for the standardisation of serological tests for IBR.