First Outbreak of an H5N8 Highly Pathogenic Avian Influenza Virus on a Chicken Farm in Japan in 2020.

Saki Sakuma,Junki Mine,Ryota Tsunekuni,Momoyo Kajita,Taichiro Tanikawa,Yuko Uchida,Takehiko Saito

doi:10.3390/v13030489

Abstract

On 5 November 2020, a confirmed outbreak due to an H5N8 highly pathogenic avian influenza virus (HPAIV) occurred at an egg-hen farm in Kagawa prefecture (western Japan). This virus, A/chicken/Kagawa/11C/2020 (Kagawa11C2020), was the first HPAI poultry isolate in Japan in 2020 and had multiple basic amino acids—a motif conferring high pathogenicity to chickens—at the hemagglutinin cleavage site. Mortality of chickens was 100% through intravenous inoculation tests performed according to World Organization for Animal Health criteria. Phylogenetic analysis showed that the hemagglutinin of Kagawa11C2020 belongs to clade 2.3.4.4B of the H5 Goose/Guangdong lineage and clusters with H5N8 HPAIVs isolated from wild bird feces collected in Hokkaido (Japan) and Korea in October 2020. These H5N8 HPAIVs are closely related to H5N8 HPAIVs isolated in European countries during the winter of 2019–2020. Intranasal inoculation of chickens with 106 fifty-percent egg infectious doses of Kagawa11C2020 revealed that the 50% chicken lethal dose was 104.63 and the mean time to death was 134.4 h. All infected chickens demonstrated viral shedding beginning on 2 dpi—before clinical signs were observed. These results suggest that affected chickens could transmit Kagawa11C2020 to surrounding chickens in the absence of clinical signs for several days before they died.

Highlights

Since 2003, highly pathogenic avian influenza viruses (HPAIVs) of the H5 subtype in which the hemagglutinin (HA) genes are derived from A/goose/Guangdong/1/1996 [1]—the so-called Goose/Guangdong (Gs/Gd) lineage—have been spreading to poultry and wild bird species worldwide, except in countries in South America and Oceania [2,3]
A cloacal swab from a dead chicken at the affected farm was inoculated into embryonated eggs; infectious allantoic fluid was examined for hemagglutination activity at the Kagawa Municipal Animal Hygiene Center and was submitted for further study at the National Institute of Animal Health of Japan
The deduced amino-acid sequence of the HA cleavage site of Kagawa11C2020 is PLREKRRKR/GLFG, which includes the run of consecutive basic amino acids that is the characteristic motif of HPAIVs [19], suggesting that Kagawa11C2020 is highly pathogenic to chickens

Summary

Introduction

Since 2003, highly pathogenic avian influenza viruses (HPAIVs) of the H5 subtype in which the hemagglutinin (HA) genes are derived from A/goose/Guangdong/1/1996 [1]. —the so-called Goose/Guangdong (Gs/Gd) lineage—have been spreading to poultry and wild bird species worldwide, except in countries in South America and Oceania [2,3]. Since the end of August 2020, H5N8 HPAIVs have been detected in wild bird and poultry species in Russia, Kazakhstan, Israel, European Union countries, and South Korea [3]. The first case of H5 HPAIVs of the Gs/Gd lineage in Japan was reported in 2004 [5]; the WHO/OIE/FAO H5N1 Evolution Working Group classified the HA gene of this isolate as belonging to clade 2.5 [6]. The HPAIVs of the Gs/Gd lineage reported in Japan in 2007, 2008, and 2010–2011 are H5N1 viruses in clades 2.2, 2.3.2, and 2.3.2.1, respectively [7,8,9]. (Kagawa11C2020: H5N8), isolated from the first H5N8 poultry case in Japan in 2020, by using genetic analysis and experiments in chickens

Virus Isolation

Sequencing

Phylogenetic Analysis

Animal Experiments

Results and Discussion

13 January