A single-radial haemolysis technique for measurement of antibody to influenza virus neuraminidase in equine sera.

A modified single-radial-haemolysis (SRH) test for measurement of antibody to influenza virus neuraminidase (NA) is described. The test requires treatment of sheep erythrocytes with butanol to increase sensitivity. In comparative assays, SRH was found to be more sensitive than the conventional neuraminidase-inhibition test. The SRH test was reproducible, specifically measured antibody to influenza NA and was easy to use. SRH antibody responses in ponies vaccinated with bivalent equine influenza vaccine were shown to be vaccine dose-related but were lower in magnitude and shorter in duration than comparable anti-haemagglutinin responses.