Data describing IAV infection and seroprevalence in Lesser and Greater Scaup

Clade 2.3.4.4b Eurasian-origin H5N1 entered North America in late 2021 and spread across the continent. While studies have characterized the antibody response mounted by dabbling ducks following exposure, little data is available for diving ducks. This study sought to identify influenza A virus (IAV) infection and antibodies in Lesser and Greater Scaup captured in Maryland, Illinois, and Rhode Island. In Maryland, IAV seroprevalence increased from the 2021/2022 to 2022/2023 sampling season, with IAV antibody prevalence increasing for juvenile (38% to 80%) and adult (82% to 90%) Lesser Scaup. While adult Lesser Scaup sampled in Illinois in 2021/2022 had IAV antibody prevalence comparable to those sampled in Maryland (76% and 82%, respectively), they had higher antibody prevalence to both H5 (48% and 18%) and N1 (68% and 35%), potentially due to being sampled in March versus December and January. Greater Scaup captured in Rhode Island had comparable IAV, H5, and N1 antibody seroprevalence to Lesser Scaup in Maryland during the same season. Our data suggest that Lesser Scaup had limited antibodies to highly pathogenic H5 IAV prior to the introduction of clade 2.3.4.4b H5N1 to North America, but relevant antibodies were widely observed in the months and year following.