Impact of highly pathogenic avian #influenza virus on Black-headed #Gulls Chroicocephalus ridibundus population in #Poland in 2023
ABSTRACT The highly pathogenic avian influenza virus (HPAIV) A(H5N1) has caused the most extensive and severe epizootic event affecting both poultry and wild birds globally. This study investigated the impact of HPAIV on the breeding population of the Black-headed Gull Chroicocephalus ridibundus , the most abundant gull species in Poland . During the 2023 outbreak, this species was reported as the most frequently infected in the country. A higher-than-natural adult mortality rate (greater than 1.5% of the breeding individuals) was observed in 114 surveyed colonies across all regions of Poland. Laboratory tests confirmed the presence of HPAIV in all 17 colonies sampled, with average adult mortality estimated at 26.1%, and ranging from 1.7% to 77.8%. The estimated mortality rate across all surveyed colonies was 22.2%. Extrapolations across the entire Polish breeding population (at least 115,000 pairs according to the national census) indicated that approximately 51,000 adult Black-headed...