Occurrence of influenza A viruses and their antibodies in migratory birds in Finland.

A Finnish material of 455 cloacal specimens from 24 species of small migratory birds and of 54 cloacal specimens from 10 species of waterfowl was investigated for the occurrence of A type influenza virus. Influenza A virus was isolated in only one specimen, originating from a mallard (Anas platyrhynchos). Parallely, yolk material from 109 waterfowl representing 9 species was investigated for the occurrence of influenza A antibodies by complement fixation and immunodiffusion tests. In three yolk specimens, one from a widgeon (Anas penelope), one from a common gull (Larus canus) and one from a lesser blackbacked gull (Larus fuscus), positive reactions with low titres of 1:2--1:4 were obtained. The study shows that waterfowl can carry influenza A virus, but the role of small migratory birds in this respect seems to be negligible in Finland.