Surveillance of Charadriiformes in Northern Australia Shows Species Variations in Exposure to Avian Influenza Virus and Suggests Negligible Virus Prevalence

The virologic surveillance of 4248 Charadriiformes since 1992 primarily from coastal northwest Australia did not detect any evidence of avian influenza virus (AIV) excretion (test prevalence = 0%; 95% confidence interval [CI]: 0%-0.09%). Past exposure to AIV was evident from serologic testing using nucleoprotein (NP) competitive-ELISA (c-ELISA) with an overall seroprevalence of 8.8% (95% CI: 8%-9.7%). The c-ELISA seroprevalence of family Scolopacidae and genus Numenius was significantly higher when compared with other families and genera, respectively. Exposure risk profiles, based on c-ELISA seroprevalence, were compiled for 40 species with the following species having significantly higher values when compared with the combined value of all other species: eastern curlew (Numenius madagascariensis), whimbrel (Numenius phaeopus), ruddy turnstone (Arenaria interpres), grey plover (Pluvialis squatarola), little curlew (Numenius minutus), red knot (Calidris canutus), sharp-tailed sandpiper (Calidris acuminata), and red-necked stint (Calidris ruficollis). From hemagglutination inhibition (HI) testing, the more prevalent HI reactions were against H2, H5, H6, and H9 subtypes, with no reactions against subtypes H11, H14, H15, and H16. Serologic testing using c-ELISA provided species risk profiles for optimizing a surveillance strategy for AIV in diverse populations of wild birds. The paucity of knowledge about the role of waders in the ecology of AIV and the overall very low to negligible virus prevalence reported globally, and in this study, suggests that waders are spillover hosts in shared ecosystems with a lesser role than previously considered.