Usutu virus-disease susceptibility in threatened red-breasted geese (Branta ruficollis) in Italy and the Netherlands

Abstract

Usutu virus (USUV) is an emerging zoonotic virus associated with mortality in birds. More than 90 species of birds have been found to be susceptible to USUV infection, but little is known about the disease susceptibility and distribution in Anseriformes. This study involved the post-mortem evaluation of four threatened red-breasted geese (Branta ruficollis). Macroscopic analysis, histology, immunohistochemistry, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and phylogenetic analysis of USUV strains were performed to evaluate the presence of USUV-associated damage, tissue tropism and involved virus strains. Macroscopic and histological lesions, represented by necrosis and mononuclear inflammation, as well as virus pan-tissue tropism, overlapped in all cases. Unlike other species, a strong involvement of endocrine organs was observed in the red-breasted geese. Two different USUV lineages, Europe 2 (in Italy) and Europe 3 (in the Netherlands), were identified as causative agents. We now report the host disease susceptibility and describe the pathology of fatal USUV-associated disease with major neurological and endocrine involvement in four threatened red-breasted geese in Italy and in the Netherlands.