Influenza A viruses and avian paramyxoviruses in wild birds

Abstract

Traditional surveillance of Influenza A viruses (IAVs) in wild birds has used RT-PCR or virus isolation. However, commercially available serological assays have been developed recently which can complement virus detection assays. This is useful because antibodies to IAVs are detectable longer than viral shedding and can be used in species that shed virus briefly or species that are not easily sampled when IAVs are circulating. In addition, serology has been an underutilized for avian paramyxovoviruses (APMVs) in wild birds. Furthermore, except for Newcastle disease virus (NDV), there is very few data on APMVs in wild birds. The objectives of this work were to use serological assays and virus isolation to determine: 1) IAV subtype-specific antibodies in Canada geese (Branta canadensis) and risk factors associated with exposure; 2) evaluate exposure of mute swans (Cygnus olor) to IAVs; and 3) the role of wood ducks (Aix sponsa) in the epidemiology of IAVs and APMVs. Canada geese were frequently exposed to the same IAVs subtypes that circulate in dabbling ducks; however, they had a high prevalence of H5-specific antibodies which are rare in ducks. There was no significant variation in antibody prevalence among years and percent developed was the only environmental predictor variable associated with risk. These data suggest that Canada geese share a common exposure with dabbling ducks and serologic data are not sensitive enough to detect local and annual variation in IAV circulation. Similarly, mute swans had a high IAVs antibody prevalence. The high nucleoprotein prevalence is likely related to antibody persistence and long life span of mute swans. The H5-specific antibody prevalence was also high which suggest mute swans may have flock immunity, which could protect them from disease associated with highly pathogenic H5N1. Wood ducks were not frequently exposed to IAVs but are frequently exposed to APMVs. These data suggest exposure of wood ducks are likely only spillover hosts and exposure is location dependent and occurs only when ducks shed IAV. Additionally, wood ducks may be important hosts of APMVs, but virus isolation data is lacking.