Newcastle disease viruses in birds in the Atlantic flyway: isolations, haemagglutination-inhibition and elution-inhibition antibody profiles.

The study involved 15 avian species with 5,012 attempts to isolate Newcastle disease viruses (NDV) from their faeces over a three-year period (1977-1979). NDV were isolated from asymptomatic adult Canada geese, nestling Royal terms, a juvenile European Mute swan, and adult Tundra swans on the Eastern flyway. Ring-billed gulls were negative for haemagglutination-inhibition (HI), elution-inhibition (EI) (anti-neuraminidase) antibodies, and NDV despite 3,403 isolation attempts. The EI antibody assay used a strain isolated from a Mute swan. The prevalence of EI antibodies in the swan and geese ranged from 3-41%, while the geometric mean titre (GMT) varied from 20-36. The prevalence of HI antibodies in the swans and geese ranged from 4-62%, while the GMT varied from 16-42. In each of three years (1977-1979), the adult Mute swans had a higher HI antibody prevalence than the juveniles (P < 0.01). Among the Mute swans the HI and EI assays detected serologic conversions and persistent antibodies over the three-year period. The HI and EI assays were effective in showing differences in antibody prevalences in populations of feral birds of different species and age. The EI assay is applicable for population studies of the anti-neuraminidase antibody.