Comparison of an antigen-capture enzyme immunoassay with virus isolation for avian influenza from field samples

The standard tests used to detect avian influenza (AI) viral infection include virus isolation from tissues of the infected birds and the detection of AI antibody in blood or egg yolk. A new application of an existing human test to rapidly detect the presence of any influenza A virus is now possible. A commercially available antigen-capture enzyme immunoassay (AC-EIA), developed for the detection of influenza A in humans was tested for relative sensitivity and specificity and for speed of use in diagnosing nonpathogenic H7N2 AI in naturally infected poultry. During the recent nonpathogenic H7N2 AI epornitic, the AC-EIA was used for rapid diagnosis and quarantine decisions. Between February and August 1997, 1524 samples from 295 commercial layer, pullet, and broiler flocks were submitted to the Laboratory of Avian Medicine and Pathology, New Bolton Center, for AI virus isolation and testing by AC-EIA. The relative specificity of the AC-EIA was 100% and the relative sensitivity was 79%. We believe that the AC-EIA will be a useful adjunct to standard AI diagnostic tests.