Type a influenza viruses in birds in southern Spain: serological survey by enzyme-linked immunosorbent assay and haemagglutination inhibition tests.

Of 927 sera taken from poultry from 84 flocks, 33% proved seropositive. Sixty-three per cent of flocks were found to be seropositive to ELISA (almost all situated within areas where there were waterfowl). The comparable figures, using an HI test, were 16% and 47%, respectively. These data suggest that the influenza A viruses may be enzootic in this area. Of 331 wild birds tested, belonging to 18 species of nine families, 40% proved seropositive to ELISA. Notable high infection rates were found among Anatidae (43%), flamingoes (43%) and sparrows (31%); the latter species may play an important role in carrying the disease from its natural reservoirs to domestic farms. Antibody titres found in wild birds were considerably higher than those found in poultry.