Serological diagnosis of influenza A infections in the horse by enzyme immunoassay. Comparison with the complement fixation test.

An enzyme immunoassay (EIA) using horseradish peroxidase and a type-specific antigen is described for the detection and quantitation of anti-influenza antibodies in the horse. Compared with the complement fixation (CF) test (using the same antigen), EIA proved to be superior with respect to sensitivity and reliability. The internal variation of EIA was low and thus small titres in EIA can be considered of diagnostic significance. However, no strict correlation with CF was observed. The use of an immunoconjugate against equine IgM in parallel with IgG would certainly improve the sensitivity of the test, especially in early stages of infection.