[Role of passerine birds in the ecology of influenza viruses].

Abstract

A total of 267 passerine birds distributed among 37 species were netted during spring 1980 and summer 1981 in the Laurentian and Montreal areas. All the cloacal swabs collected at that time wer free of influenza viruses. Three and five days after oral administration of avian or human influenza A virus strains, 108 isolates were obtained from 42 of 134 passerine birds. Positive samples were recovered mainly from the respiratory and the digestive tract and also from liver. Spleen and kidneys. Viral replication is cells from trachea, lungs, gizzard and caecum was detected by indirect immunofluorescence using a monoclonal antibody to influenza A virus nucleoprotein. Viral transmission from inoculated to non inoculated birds placed in the same cages was not observed. On the other hand a similar experimental inoculation of young mallard ducks showed that extensive viral transmission occurred from inoculated to non inoculated ducklings and that infection was found exclusively in the digestive tract. Furthermore viruses were detected in samples of drinking water from all cages containing infected ducks. Passerine birds do not represent an important reservoir of influenza viruses but might contribute to the formation and spreading of recombinants potentially pathogenic for man and animals.