Epidemiological dominance of the most virulent HPAIV H5N1 clade 2.3.4.4b strains: insights from experimental infections of Pekin ducks (Anas platyrynchos): [Preprint]
Highly pathogenic avian influenza H5 viruses (HPAIV) pose an ongoing threat to wild birds and domestic poultry worldwide. The emergence and establishment of clade 2.3.4.4b viruses in European wild birds since 2021 marked a significant epidemiological shift with transcontinental transmission to the A...
| Main Authors: | , , , , , , , |
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| Format: | Report |
| Language: | English |
| Published: |
Research Square Platform LLC
2024
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| Subjects: | |
| Online Access: | https://doi.org/10.21203/rs.3.rs-4486200/v1 https://www.openagrar.de/receive/openagrar_mods_00097098 https://www.openagrar.de/servlets/MCRFileNodeServlet/openagrar_derivate_00059790/10.21203rs.3.rs-4486200v1_Preprint.pdf https://www.researchsquare.com/article/rs-4486200/v1 https://assets-eu.researchsquare.com/files/rs-4486200/v1/c666f2a8-97ce-43ad-8768-6b5b5a7ccae1.pdf |
| Summary: | Highly pathogenic avian influenza H5 viruses (HPAIV) pose an ongoing threat to wild birds and domestic poultry worldwide. The emergence and establishment of clade 2.3.4.4b viruses in European wild birds since 2021 marked a significant epidemiological shift with transcontinental transmission to the Americas and Antarctic waters by the end of 2023. This study investigates the virulence of nine HPAI H5N1 genotypes co-circulating during the autumn and winter seasons of 2021 and 2022 in Germany. Contrary to the "avirulence hypothesis", the most virulent genotypes in ducklings showed epidemiological dominance in the field. Virulence in ducklings was assessed by the intramuscular pathotyping index (IMPI). In addition, occulo-nasal infection of ducklings with two representative viruses of high and intermediate IMPI score confirmed phenotypes obtained by IMPI. The intermediate strain revealed decelerated low-level virus replication with almost no enteral shedding but (transient) neurological infection. Comparison of the genetic constellation of the nine different genotypes point to an important role of the viral polymerase complex (RdRP), particularly the PB1 genome segment, in shaping virulence and infection dynamics in ducklings. Overall, the results are in favour of the 'virulence-transmission trade-off' model for the previous HPAI panzootic in Germany, suggesting that the population size of susceptible hosts has not been a limiting factor for the spread of HPAI viruses. Breaking such transmission cycles would depend on diminishing host reservoirs due to fatal losses or gradually increasing population immunity in wild birds. In poultry, vaccination might help reducing susceptibility and mitigating the threat of HPAI outbreaks. |
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