Highly Pathogenic Avian Influenza (HPAI H5Nx, Clade 2.3.4.4.b) in Poultry and Wild Birds in Sweden: Synopsis of the 2020-2021 Season

Simple Summary Highly pathogenic avian influenza is a virus-induced contagious disease that has killed a large number of poultry and wild birds in Europe in the recent decade and is an increasing problem worldwide. In the winter of 2020-2021, Sweden experienced its worst period to date when the disease was diagnosed on 15 commercial poultry farms and over 2.2 million birds died or were euthanised. The disease was also diagnosed in 130 wild birds and nine flocks of hobby, game or zoo birds between 1 October 2020 and 30 September 2021. The aim of this article was to describe the influenza situation in Sweden during this period and to add to the knowledge related to the alarming situation with highly pathogenic influenza in birds. The disease caused animal suffering and death in wild and domestic birds and incurred high costs due to losses and extensive measures to stop spread. The outbreak investigations, where contacts were traced and virus strains were compared, concluded that the virus was brought to poultry farms by wild birds in most cases. More research is needed to obtain knowledge on risk factors, biosecurity, and wild bird presence on poultry farms to prevent future disease outbreaks. Highly pathogenic avian influenza (HPAI, Gs/Gd lineage) was introduced to Europe in 2005 and has since caused numerous outbreaks in birds. The 2020-2021 season was the hitherto most devastating when considering bird numbers and duration in Europe. Surveillance data, virologic results and epidemiologic investigations from the 2020-2021 outbreaks in Sweden were analysed. Subtypes H5N8 and H5N5 were detected on 24 farms with poultry or other captive birds. In wild birds, subtypes H5N8, H5N5, H5N1, H5N4, H5Nx were detected in 130 out of 811 sampled birds. There was a spatiotemporal association between cases in wild birds and poultry. Based on phylogeny and epidemiology, most of the introductions of HPAI to commercial poultry were likely a result of indirect contact with wild birds. A definite route of introduction to poultry could not be established although some biosecurity breaches were observed. No spread between farms was identified but airborne spread between flocks on the same farm was suspected. Our findings exemplify the challenges posed by the continuously changing influenza viruses that seem to adapt to a broader species spectrum. This points to the importance of wild bird surveillance, compliance to biosecurity, and identification of risk factors for introduction on poultry farms

Detection of gastric Helicobacter species in free-ranging lynx (Lynx lynx) and red foxes (Vulpes vulpes) in Sweden

Specimens of gastric mucosa and liver of 25 free-ranging Eurasian lynx (Lynx lynx), and four red foxes (Vulpes vulpes) shot in Sweden during 1999-2000, were investigated for the presence of Helicobacter species. Histopathology, bacteriologic culture and urease test, Helicobacter genus-specific 16S rDNA PCR analysis, and DNA sequence analysis were applied. Numerous Helicobacter-like organisms were observed histologically in the gastric mucosa of one fox. Helicobacter spp. were detected in the stomach by PCR analysis in 17 (68%) of the lynx and in three (755) of the foxes. Seven of the positive lynx were also positive in the urease test. PCR fragments, amplified from lynx and foxes, were sequenced and compared with those of known Helicobacter species. PCR products from lynx were closely related (>= 98% homology) to H. heilmannii, and PCR fragments from foxes demonstrated close homology to H. heilmannii and H. salomonis. No Helicobacter spp. or Helicobacter-like organisms could be cultured. The PCR analysis of the liver was negative for all animals, The pathologic significance of the presence of Helicobacter spp. in the stomach of free-ranging lynx and foxes remains uncertain