Molecular Characterization of Highly Pathogenic Avian Influenza Viruses H5N6 Detected in Denmark in 2018–2019

Abstract

Beginning in late 2017, highly pathogenic avian influenza (HPAI) H5N6 viruses caused outbreaks in wild birds and poultry in several European countries. H5N6 viruses were detected in 43 wild birds found dead throughout Denmark. Most of the Danish virus-positive dead birds were found in the period from February to April 2018. However, unlike the rest of Europe, sporadic HPAI H5N6-positive dead wild birds were detected in Denmark in July, August, September, and December 2018, with the last positive bird being found in January 2019. HPAI viruses were not detected in active surveillance of apparently healthy wild birds. In this study, we use full genome sequencing and phylogenetic analysis to investigate the wild bird HPAI H5N6 viruses found in Denmark. The Danish viruses were found to be closely related to those of contemporary HPAI H5N6 viruses detected in Europe. Their sequences formed two clusters indicating that at least two or more introductions of H5N6 into Denmark occurred. Notably, all viruses detected in the latter half of 2018 and in 2019 grouped into the same cluster. The H5N6 viruses appeared to have been maintained undetected in the autumn 2018.

Characterization of high pathogenicity avian influenza H5Nx viruses from a wild harbor seal and red foxes in Denmark, 2021 and 2022

“…In 2022, HPAIV H5N1 was detected in one adult red fox and three red fox cubs ( Vulpes vulpes ) by rRT‐PCR and sequencing 2 . Brain and/or lung tissues from the four foxes were collected for virological and histopathological analyses.…”

“…The organs were also tested for the presence of pathogenic bacteria and morbillivirus as previously described, 1 in which none tested positive. The presence of clade 2.3.4.4b HPAIV H5N8 was confirmed in the lung of the seal by real‐time RT‐PCR (rRT‐PCR) and sequencing as previously described 2 (Table 1 ).…”

“…In 2022, HPAIV H5N1 was detected in one adult red fox and three red fox cubs ( Vulpes vulpes ) by rRT‐PCR and sequencing. 2 Brain and/or lung tissues from the four foxes were collected for virological and histopathological analyses. The adult fox was found dead on January 17, 2022, close to a fox pit at Djursland in Eastern Jutland, where HPAIV H5N1 was detected in the lung (Table 1 ).…”

Avian influenza revisited: concerns and constraints

“…The result of LAMP reactions can be interpreted by direct visual inspection and limit of detection is equivalent to that of RT-PCR [1,23]. The Next-generation sequencing (NGS) analyses using targeted and whole-genome sequencing is an upcoming technique with an ability to provide complete description of the genetic, chronological, and geographical aspects of the outbreak [28]. NGS enables study of high-resolution molecular epidemiology and highlights the importance of poultry as a source of novel genetic variations originated from multiple reassortment events [27,50].…”

Transmission dynamics and pathogenesis differ between pheasants and partridges infected with clade 2.3.4.4b H5N8 and H5N1 high-pathogenicity avian influenza viruses

“…The European H5N8 clade 2.3.4.4b HPAIV epizootic during 2016–2017 included UK pheasant farm outbreaks which featured frequent mortality [20]. More recently, the clade 2.3.4.4b H5N6 HPAIV cases in Danish wild birds during summer 2018 included detections in wild pheasants which again drew attention to their potential bridging role, although no commercial chicken premises were affected [26]. In an in vivo investigation, H5N6 HPAIV direct infection of pheasants initiated efficient onward transmission via introduced contact pheasants, despite high mortality [27].…”