The perpetuation of orthomyxoviruses and paramyxoviruses in Canadian waterfowl

Abstract

A longitudinal survey of viruses in feral ducks from 1976 to 1978 in the Vermillion area of Alberta, Canada, has shown that influenza A viruses and paramyxoviruses are present year after year in these apparently healthy ducks. Influenza viruses were isolated most frequently each year from mallards, pintails, and blue-winged teals, but were not restricted to these species. During the 3-year survey, 1262 influenza viruses were isolated from 4827 ducks, revealing the high incidence of influenza infection, a finding which contrasts with the very low incidence found in ducks during migration through Tennessee.Many different influenza A viruses were detected in the ducks, including 27 different combinations of hemagglutinin and neuraminidase subtypes. These viruses encompass all but one of the known hemagglutinin and neuraminidase subtypes. The virus subtypes in the ducks varied from year to year; however, 6 of these 27 subtypes were present every year. The predominant subtype changed from Hav7Neq2 in 1976–1977 to Hav6N2 in 1978. Antigenic comparisons of current and previous Hav6 viruses isolated from ducks, turkeys, and a shearwater showed that antigenic drift occurs in avian influenza viruses.Paramyxoviruses occur in the Canadian ducks at a much lower frequency than influenza viruses; in 3 years, 69 paramyxoviruses were isolated and included two types: lentogenic NDV and Duck/Mississippi/75.These longitudinal studies indicate that the feral ducks in the study area of Canada are a perpetual reservoir of diverse influenza A viruses and paramyxoviruses.