Abstract
HPAI can spread over long distances through bird migration. Denmark, centrally located on migration routes for 500 million birds, is at high risk of HPAI outbreaks. Since 2020, HPAI virus-infected wild birds have been detected every season in Denmark’s wild bird surveillance system, and poultry outbreaks have occurred. This study describes HPAI detections in wild birds and the epidemiological characterizations of infected poultry farms over four seasons.
A total of 845 wild birds tested positive for HPAI with spatial and temporal variations across seasons. In the 20/21 season, viruses of the H5N8 subtype dominated alongside a silent summer period. In the 21/22 season, H5N1 dominated, less seasonality was observed and seabird colonies were affected during the summer. The 22/23 season was again dominated by H5N1, still with outbreaks in domestic birds in all seasons, but overall fewer detections in wild birds, and this trend continued in the 23/24 season.
In total, 49 outbreaks were detected in poultry and captive birds. Danish turkey farms have been most often infected, with 3-4 outbreaks in each season. Outbreaks occurred across all farm types and all species, from hobby farms with low biosecurity to large commercial farms with high biosecurity.. Clinical signs included increased mortality, depression, respiratory and gastro-intestinal symptoms. Identifying the cause of introduction in outbreak farms was rarely possible. Virus detected in poultry and captive birds were genetically closely related to virus from contemporary wild birds.
A total of 845 wild birds tested positive for HPAI with spatial and temporal variations across seasons. In the 20/21 season, viruses of the H5N8 subtype dominated alongside a silent summer period. In the 21/22 season, H5N1 dominated, less seasonality was observed and seabird colonies were affected during the summer. The 22/23 season was again dominated by H5N1, still with outbreaks in domestic birds in all seasons, but overall fewer detections in wild birds, and this trend continued in the 23/24 season.
In total, 49 outbreaks were detected in poultry and captive birds. Danish turkey farms have been most often infected, with 3-4 outbreaks in each season. Outbreaks occurred across all farm types and all species, from hobby farms with low biosecurity to large commercial farms with high biosecurity.. Clinical signs included increased mortality, depression, respiratory and gastro-intestinal symptoms. Identifying the cause of introduction in outbreak farms was rarely possible. Virus detected in poultry and captive birds were genetically closely related to virus from contemporary wild birds.
Co-Author(s)
Anette Ella Boklund, University of Copenhagen,
Yuan Liang, , University of Copenhagen,
Lars Erik Larsen, University of Copenhagen,
Carsten Kirkeby, University of Copenhagen,
Lene Jung Kjær, University of Copenhagen,
Helene Ane Jensen, , University of Copenhagen,
Charlotte Kristiane Hjulsager, Statens Serum Institut
Abstract Category
Biosecurity, mitigation, control, and post-epidemic considerations in poultry