Abstract
During the 2020–2021 winter season, an outbreak of clade 2.3.4.4b H5N8 high pathogenicity avian influenza (HPAI) virus occurred in South Korea. Here, we evaluated the pathogenicity and transmissibility of A/mandarin duck/Korea/H242/2020 (H5N8) (H242/20(H5N8)) first isolated from this outbreak in specific pathogen-free (SPF) chickens and commercial ducks in comparison with those of A/duck/Korea/HD1/2017(H5N6) (HD1/17(H5N6)) from a previous HPAI outbreak in 2017–2018. In chickens, the 50% chicken lethal dose and mean death time of H242/20(H5N8) group were 104.5 EID50 and 4.3 days, respectively, which indicate less virulent than those of HD1/17(H5N6) (103.6 EID50 and 2.2 days). Whereas, chickens inoculated with H242/20(H5N8) survived longer and had a higher titer of viral shedding than those inoculated with HD1/17(H5N6), which may increase the risk of viral contamination on farms. All ducks infected with either HPAI virus survived without clinical symptoms. In addition, they exhibited a longer virus shedding period and a higher transmission rate, indicating that ducks may play an important role as a silent carrier of both HPAI viruses. These results suggest that the pathogenic characteristics of HPAI viruses in chickens and ducks need to be considered to effectively control HPAI outbreaks in the field.
Highlights
Accepted: 19 September 2021Since 1997, high pathogenicity avian influenza (HPAI) H5 viruses of the A/goose/Guangdong/1/1996 (Gs/GD) lineage have caused outbreaks in countries worldwide and have evolved continuously into diverse clades and subgroups
Its pathogenicity was compared with that of A/duck/Korea/HD1/2017(H5N6) (HD1/17(H5N6)), which was isolated from a commercial duck farm during the 2017–2018 HPAI outbreak in Korea [7]
An intravenous pathogenicity index (IVPI) test with specific pathogen-free (SPF) chickens was performed according to the instructions in the World Organization of Animal
Summary
Since 1997, high pathogenicity avian influenza (HPAI) H5 viruses of the A/goose/. Guangdong/1/1996 (Gs/GD) lineage have caused outbreaks in countries worldwide and have evolved continuously into diverse clades and subgroups. In 2017–2018, a H5N6 virus from different subclade (clade 2.3.4.4b) caused an outbreak on poultry farms [7,8]. The pathogenicity and transmissibility of HPAI viruses belonging to clade 2.3.4.4 vary according to genetic differences [3,6,9,10,11,12,13,14]. In October 2020, clade 2.3.4.4b H5N8 virus was first isolated from wild birds and was identified in a domestic duck farm in Korea one month later. The H5N8 HPAI virus that first circulated during the 2020–2021 outbreak in Korea is genetically close to viruses reported in Europe during 2019–2020 [15,16,17,18]. 2020–2021 HPAI outbreak, in specific pathogen-free (SPF) chickens and commercial ducks
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