Genetic and biological characteristics of the globally circulating H5N8 avian influenza viruses and the protective efficacy offered by the poultry vaccine currently used in China

Pengfei Cui,Yaping Zhang,Jing Guo,Xuyong Li,Yanbing Li,Qi Ma,Guobin Tian,Hongmei Bao,Wenli Gu,Minghui Li,Guohua Deng,Yuancheng Zhang,Conghui Zhao,Xianying Zeng,Chengjun Liu ,Jianzhong Shi,Yanwen Wang,Dongxue Wang,Jingman Tian,Zhiyuan Qu,Yanjing Liu,Xinpeng Xing ,Liling Liu,Weipeng Lin,Shuxin Pan,Hualan Chen

doi:10.1007/s11427-021-2025-y

Abstract

The H5N8 avian influenza viruses have been widely circulating in wild birds and are responsible for the loss of over 33 million domestic poultry in Europe, Russia, Middle East, and Asia since January 2020. To monitor the invasion and spread of the H5N8 virus in China, we performed active surveillance by analyzing 317 wild bird samples and swab samples collected from 41,172 poultry all over the country. We isolated 22 H5N8 viruses from wild birds and 14 H5N8 viruses from waterfowls. Genetic analysis indicated that the 36 viruses formed two different genotypes: one genotype viruses were widely detected from different wild birds and domestic waterfowls; the other genotype was isolated from a whopper swan. We further revealed the origin and spatiotemporal spread of these two distinct H5N8 virus genotypes in 2020 and 2021. Animal studies indicated that the H5N8 isolates are highly pathogenic to chickens, mildly pathogenic in ducks, but have distinct pathotypes in mice. Moreover, we found that vaccinated poultry in China could be completely protected against H5N8 virus challenge. Given that the H5N8 viruses are likely to continue to spread in wild birds, vaccination of poultry is highly recommended in high-risk countries to prevent H5N8 avian influenza.

Highlights

Influenza viruses bearing the H5 hemagglutinin (HA) have been circulating in wild birds and domestic poultry for over two decades since the H5N1 virus was detected in China in 1996 (Harfoot and Webby, 2017)
A total of 36 H5N8 avian influenza viruses were isolated from these samples: 22 viruses were isolated from dead wild birds and wild bird feces found in a variety of habitats (Table 1), and eight and six viruses were isolated from duck swabs and goose swabs, respectively, that were collected in live poultry markets and slaughterhouses (Table 1)
There is a clear antigenic difference between the H5N8 viruses and the H5N1 vaccine strains currently used in China, vaccinated chickens and ducks in poultry farms could be completely protected against H5N8 virus challenge

Summary

Introduction

Influenza viruses bearing the H5 hemagglutinin (HA) have been circulating in wild birds and domestic poultry for over two decades since the H5N1 virus was detected in China in 1996 (Harfoot and Webby, 2017). The viruses were subsequently spread by whooper swans to Mongolia and Russia in August 2005, and were widely detected in wild birds and domestic poultry in European and African countries in 2006 (Olsen et al, 2006). These viruses were eradicated in China and many other countries in a relatively short time, but they circulated in poultry for many years and caused severe disease in poultry and humans in Egypt (ElShesheny et al, 2021)

Methods

Results

Conclusion