a1 Department of Biostatistics and Epidemiology, The University of Tennessee, Memphis, 877 Madison Avenue (Suite 330), Memphis, Tennessee, 38163, USA
a2 Department of Virology and Molecular Biology, St Jude Children's Research Hospital, 332 North Lauderdale, Memphis, Tennessee, 38105, USA
a3 Canadian Wildlife Service, 4999–98th Avenue (Room 210), Edmonton, Alberta, T6B, 2X3, Canada
a4 University of Wisconsin-Madison, School of Veterinary Medicine, Department of Pathobiological Sciences, 2015 Linden West, Madison, Wisconsin, 53706, USA
Analysis of cloacal samples collected from 12321 wild ducks in Alberta, Canada, from 1976 to 1990 showed influenza A infections to be seasonal, with prevalences increasing as the population became increasingly more dense. Viruses with 3 haemagglutinin (H3, H4, and H6) and 3 neuraminidase subtypes (N2, N6, and N8) were found consistently to infect both adult and juvenile ducks each year, indicating that wild ducks may be a reservoir for these viruses. In contrast, viruses with 7 haemagglutinin (H2, H5, H7, H8, H9, H11, and H12) and 3 neuraminidase subtypes (N1, N3, and N4) were not found for prolonged periods during the study; when they were found, they primarily infected juveniles at moderate levels. Whilst wild ducks appear to perpetuate some influenza A viruses, they apparently do not act as a reservoir for all such viruses.
(Accepted September 16 1992)