Highly Pathogenic Avian #Influenza A(#H5N1) Caused Mass Death among Black-legged #Kittiwakes (Rissa tridactyla) in #Norway, 2023
Abstract In 2023, highly pathogenic avian influenza (HPAI) heavily affected gulls in Europe. In July, a mass mortality event was reported in the Black-legged Kittiwake (Rissa tridactyla) breeding colony at Ekkerøy in Northern Norway . The cause was confirmed to be infection with the HPAI H5N1 clade 2.3.4.4b virus , genotype EA-2022- BB. We describe the outbreak in Kittiwakes, including pathological and virological investigations , and discuss the management and zoonotic potential . With more than 15,000 dead birds reported , we estimate that the outbreak caused a reduction in the Kittiwake population at Ekkerøy of at least 50%. Diseased birds exhibited neurological signs . Necropsy of ten birds revealed a peracute fatal systemic disease , with severe lesions in the brain and pancreas co-localizing with the presence of viral RNA and antigen. Vascular expression of α2,3-linked sialic acids and viral RNA/antigen may reflect hematogenous virus spread . Further studies should investigate th...