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Abstract Title
Genetic and serological analysis of high pathogenicity H5N1 avian influenza viruses in Izumi plain, Japan, during the 2022/23 and 2023/24 seasons
Abstract
The Izumi plain serves as one of the largest overwintering habitat for endangered cranes in the world, supporting approximately 80% of the global Hooded Crane population and 75% of the White-naped Crane population. To monitor the prevalence of high pathogenicity avian influenza (HPAI) in this area, an avian influenza surveillance system was established, including virus isolation from sacrificed wild birds and from weekly collected environmental water samples for over a decade.
During the 2022/23 winter season, the first mass mortality event among the endangered cranes was observed in the Izumi plain, with a total of 1,504 cranes found debilitated or dead. Most of these cranes, especially those collected in November 2022, were confirmed to be infected with H5N1 HPAI viruses. Genetic analysis suggested that the primary transmission route of the H5N1 HPAI among the cranes was respiratory rather than waterborne. Serological analysis suggested that herd immunity played a limited role in the decline of the outbreak.
In the following 2023/24 winter season, only eight cranes tested positive for H5N1 HPAI viruses, which belonged to a different genetic lineage from the previous season's HPAI viruses. Serological tests showed no seropositivity for H5 HPAI viruses among the sampled cranes, again suggesting that herd immunity had a minimal impact on preventing the spread of H5N1 HPAI viruses among cranes. Since the effect of herd immunity in preventing HPAI outbreaks is limited, there remains a possibility of large-scale outbreaks in the future, highlighting the need for continuous monitoring.
During the 2022/23 winter season, the first mass mortality event among the endangered cranes was observed in the Izumi plain, with a total of 1,504 cranes found debilitated or dead. Most of these cranes, especially those collected in November 2022, were confirmed to be infected with H5N1 HPAI viruses. Genetic analysis suggested that the primary transmission route of the H5N1 HPAI among the cranes was respiratory rather than waterborne. Serological analysis suggested that herd immunity played a limited role in the decline of the outbreak.
In the following 2023/24 winter season, only eight cranes tested positive for H5N1 HPAI viruses, which belonged to a different genetic lineage from the previous season's HPAI viruses. Serological tests showed no seropositivity for H5 HPAI viruses among the sampled cranes, again suggesting that herd immunity had a minimal impact on preventing the spread of H5N1 HPAI viruses among cranes. Since the effect of herd immunity in preventing HPAI outbreaks is limited, there remains a possibility of large-scale outbreaks in the future, highlighting the need for continuous monitoring.
Co-Author(s)
Mana Esaki 1, Kosuke Okuya 1,2, Kaori Tokorozaki 3, Yuko Haraguchi 3, Masanobu Horie 3, and Makoto Ozawa 1,2,* 1 Joint Graduate School of Veterinary Medicine, Kagoshima University, Kagoshima, Japan 2 Department of Pathogenetic and Preventive Veterinary Science, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan 3 Kagoshima Crane Conservancy, Kagoshima, Japan * Correspondence: mozawa@vet.kagoshima-u.ac.jp Presenter: k0068103@kadai.jp
Abstract Category
Notable outbreaks, field and molecular epidemiology, and surveillance in wild birds