Novel H5N6 avian influenza virus reassortants with European H5N8 isolated in migratory birds, China

Evaluating the Impact of Low-Pathogenicity Avian Influenza H6N1 Outbreaks in United Kingdom and Republic of Ireland Poultry Farms during 2020

In January 2020, increased mortality was reported in a small broiler breeder flock in County Fermanagh, Northern Ireland. Gross pathological findings included coelomitis, oophoritis, salpingitis, visceral gout, splenomegaly, and renomegaly. Clinical presentation included inappetence, pronounced diarrhoea, and increased egg deformation. These signs, in combination with increased mortality, triggered a notifiable avian disease investigation. High pathogenicity avian influenza virus (HPAIV) was not suspected, as mortality levels and clinical signs were not consistent with HPAIV. Laboratory investigation demonstrated the causative agent to be a low-pathogenicity avian influenza virus (LPAIV), subtype H6N1, resulting in an outbreak that affected 15 premises in Northern Ireland. The H6N1 virus was also associated with infection on 13 premises in the Republic of Ireland and six in Great Britain. The close genetic relationship between the viruses in Ireland and Northern Ireland suggested a direct causal link whereas those in Great Britain were associated with exposure to a common ancestral virus. Overall, this rapidly spreading outbreak required the culling of over 2 million birds across the United Kingdom and the Republic of Ireland to stamp out the incursion. This report demonstrates the importance of investigating LPAIV outbreaks promptly, given their substantial economic impacts.

Prevalence of Antibiotic Resistance and Virulence Genes in Escherichia coli Carried by Migratory Birds on the Inner Mongolia Plateau of Northern China from 2018 to 2023

(1) Background: Antibiotic resistance in bacteria is an urgent global threat to public health. Migratory birds can acquire antibiotic-resistant and pathogenic bacteria from the environment or through contact with each other and spread them over long distances. The objectives of this study were to explore the relationship between migratory birds and the transmission of drug-resistant pathogenic Escherichia coli. (2) Methods: Faeces and swab samples from migratory birds were collected for isolating E. coli on the Inner Mongolia Plateau of northern China from 2018 to 2023. The resistant phenotypes and spectra of isolates were determined using a BD Phoenix 100 System. Conjugation assays were performed on extended-spectrum β-lactamase (ESBL)-producing strains, and the genomes of multidrug-resistant (MDR) and ESBL-producing isolates were sequenced and analysed. (3) Results: Overall, 179 isolates were antibiotic-resistant, with 49.7% MDR and 14.0% ESBL. Plasmids were successfully transferred from 32% of ESBL-producing strains. Genome sequencing analysis of 91 MDR E. coli strains identified 57 acquired resistance genes of 13 classes, and extraintestinal pathogenic E. coli and avian pathogenic E. coli accounted for 26.4% and 9.9%, respectively. There were 52 serotypes and 54 sequence types (STs), including ST48 (4.4%), ST69 (4.4%), ST131 (2.2%) and ST10 (2.2%). The international high-risk clonal strains ST131 and ST10 primarily carried blaCTX-M-27 and blaTEM-176. (4) Conclusions: There is a high prevalence of multidrug-resistant virulent E. coli in migratory birds on the Inner Mongolian Plateau. This indicates a risk of intercontinental transmission from migratory birds to livestock and humans.

Genetic Characterization and Pathogenesis of Avian Influenza Virus H3N8 Isolated from Chinese pond heron in China in 2021

In October 2021, a wild bird-origin H3N8 influenza virus-A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8)-was isolated from Chinese pond heron in China. Phylogenetic and molecular analyses were performed to characterize the genetic origin of the H3N8 strain. Phylogenetic analysis revealed that eight gene segments of this avian influenza virus H3N8 belong to Eurasian lineages. HA gene clustered with avian influenza viruses is circulating in poultry in southern China. The NA gene possibly originated from wild ducks in South Korea and has the highest homology (99.3%) with A/Wild duck/South Korea/KNU2020-104/2020 (H3N8), while other internal genes have a complex and wide range of origins. The HA cleavage site is PEKQTR↓GLF with one basic amino acid, Q226 and T228 at HA preferentially bind to the alpha-2,3-linked sialic acid receptor, non-deletion of the stalk region in the NA gene and no mutations at E627K and D701N of the PB2 protein, indicating that isolate A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) was a typical avian influenza with low pathogenicity. However, there are some mutations that may increase pathogenicity and transmission in mammals, such as N30D, T215A of M1 protein, and P42S of NS1 protein. In animal studies, A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) replicates inefficiently in the mouse lung and does not adapt well to the mammalian host. Overall, A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) is a novel wild bird-origin H3N8 influenza virus reassortant from influenza viruses of poultry and wild birds. This wild bird-origin avian influenza virus is associated with wild birds along the East Asian-Australasian flyway. Therefore, surveillance of avian influenza viruses in wild birds should be strengthened to assess their mutation and pandemic risk in advance.

Highly Pathogenic Avian Influenza A(H5N8) Clade 2.3.4.4b Viruses in Satellite-Tracked Wild Ducks, Ningxia, China, 2020

During October 2020, we identified 13 highly pathogenic avian influenza A(H5N8) clade 2.3.4.4b viruses from wild ducks in Ningxia, China. These viruses were genetically related to H5N8 viruses circulating mainly in poultry in Europe during early 2020. We also determined movements of H5N8 virus‒infected wild ducks and evidence for spreading of viruses.

H5 low pathogenic avian influenza viruses maintained in wild birds in China

Low pathogenic avian influenza virus, H5 or H7 subtype, possesses the potential capability to change to highly pathogenic variant, which damages wild waterfowl, domestic poultry, and mammalian hosts. In regular active surveillance of avian influenza virus from wild birds in China in 2020, we isolated six H5 avian influenza viruses, including one H5N2, two H5N3, and three H5N8. Phylogenetic analysis indicated that the H5N2 and H5N3 isolates clustered into Eurasian lineage, whereas the H5N8 viruses were originated in North America. The HA proteins of six viruses carried the cleavage-site motif PQRETR↓GLF, which indicated low pathogenicity of the viruses in chickens. However, the N30D, I43M, and T215A mutations in M1 protein and the P42S, I106M, and C138F residues changed in NS1 protein, implying all viruses could exhibit increased virulence in mice. Viral replication kinetics in mammalian cells demonstrated that the three representative viruses had the ability to replicate in both MDCK cells and A549 cells with low titers. Even though two of three representatives, WS/SX/S3-620/2020(H5N3) and ML/AH/A3-770/2020(H5N8), did not replicate and transmit efficiently in poultry (chickens), they did replicate and transmit efficiently in waterfowl (ducks). Viral pathogenicity in mice indicated that both H5N2 and H5N3 viruses are able to replicate in the nasal turbinates and lungs of mice without prior adaptation, while the H5N8 virus could not. The intercontinental and cross-species transmission of viruses may continuously exist in China, thereby providing constant opportunities for virus reassortment with local resident AIVs. Thus, it is crucial to continuously monitor migration routes for AIVs by systematic surveillance.

Pathological analysis and genetic characterization of the first outbreak H5N8 subtype avian influenza virus isolated from wild swan in Shandong, China

In January 2021, an outbreak of H5N8 subtype avian influenza was identified from wild mute swans (Cygnus olor) in an overwintering site located within Yellow River Delta Nature Reserve in Shandong, China, for the first time. We sequenced the hemagglutinin (HA) and neuraminidase (NA) genome segments of the virus, named A/mute swan/Shandong/1/2021 (H5N8), and explored the genetic characterization and comparative phylogenetic analysis to track its origin. The wild swans prior to death showed nervous signs accompanied by a twisted neck. The major pathological changes of the heart, lung, trachea, kidney, spleen, and glandular stomach were hemorrhage, and extensive necrotic lesions in the liver and pancreas were also observed. Further analysis of the HA and NA phylogenetic trees generated by H5N8 strains isolated worldwide revealed that the isolate has a close genetic relationship with the H5N8 subtype avian influenza virus (AIV) recently isolated in Korea and Japan from 2020 to 2021, suggesting the potential role of mute swans in the global dissemination of the H5N8 subtype AIVs along the migration routes. Therefore, enhanced active surveillance in wild and domestic birds is required to monitor the introduction and spread of the H5N8 subtype AIV by migratory birds in order to decrease the risk of H5N8 outbreaks.

Genetic analysis and biological characteristics of novel clade 2.3.4.4 reassortment H5N6 avian influenza viruses from poultry in eastern China in 2016

OBJECTIVES

The continuous evolution of highly pathogenic H5N6 avian influenza viruses (AIVs) causes outbreaks in wildfowl and poultry, and occasional human infections. The aim of this study was to better understand the genetic relationships between these H5N6 AIVs from eastern China and other AIVs.

METHODS

In 2016, 1623 cloacal swabs were sampled from poultry in 18 LPMs in eastern China, and subsequently characterized systematically using gene sequencing, phylogenetic studies, and antigenic analysis. In addition, their pathogenicity in mammals was studied in BALB/c mice, which were inoculated with viruses, with survival rate and body weight recorded daily for 14 days.

RESULTS

In total, 56 H5N6 AIVs were isolated in eastern China and five representative isolates were selected for further study. In our study, the H5N6 AIVs clustered into clade 2.3.4.4, Group C, and their six internal segments were derived from H6N6 and H9N2 viruses, or both, suggesting extensive reassortant among H5N6 AIVs with other subtypes. These H5N6 viruses could replicate in the lungs without prior adaptation, and exhibited slight-to-moderate virulence in mice.

CONCLUSIONS

The continuous circulation of these novel H5N6 viruses suggests the importance of persistent surveillance of H5N6 AIVs in poultry.

Maternal transfer of antibodies specific for avian influenza viruses in captive whooper swans (Cygnus cygnus)

The transfer of maternal antibodies to offspring can effectively protect against avian influenza virus (AIV) infection during early life in chickens and can prevent AIV spread by decreasing the overall percentage of the avian population susceptible to this pathogen. Herein, we evaluated maternal antibody transfer dynamics in whooper swans (Cygnus cygnus), which represent an important AIV host species. In total, 57 eggs from 19 nests were collected to study the relationship between egg yolk AIV-specific antibody concentrations and factors including egg size, laying order, maternal serum AIV antibody titer, and maternal body condition. Overall, we found that AIV-specific antibodies were present in the serum of 63.2 % of surveyed female swans and were transferred to 50.8 % of analyzed eggs. We found maternal AIV-specific antibody concentration and body weight to be positively correlated with egg yolk AIV antibody concentration, whereas egg laying order was negatively correlated with yolk antibody titer. Overall, these findings maternal transfer of AIV-specific antibodies may function as a key mechanism governing the dynamics of AIV infection in swan populations.

Surveillance of multiple subtype specific antibodies against avian influenza viruses among egg yolk in wild ducks from northeast China, 2017-2019

Over the past decade, various avian influenza viruses have been isolated from wild ducks found in the northeast of China. To monitor the prevalence of multiple subtype specific AIVs antibodies, 1705 wild ducks' eggs from six wetlands of northeast China were analyzed for surveillance of H1, H3, H5, and H7 AIVs antibodies by c-ELISA and HI test from Jan 2017 to Dec 2019. The results show that the combined frequency of multiple subtype specific AIVs antibodies were H1 (12.32%), H3 (8.15%), H5 (2.05%), and H7 (3.46%) respectively. Therefore, a detailed analysis of the geographical distribution of AIVs in China, and the risk factors for human infection is of vital importance. This study provides basic data for other researchers to deeply study AIVs distribution characteristics, and for governments to develop detailed measures to control the spread of AIVs.

Diversity of avian influenza A(H5N6) viruses in wild birds in southern China

The predominance of H5N6 in ducks and continuous human cases have heightened its potential threat to public health in China. Therefore, the detection of emerging variants of H5N6 avian influenza viruses has become a priority for pandemic preparedness. Questions remain as to its origin and circulation within the wild bird reservoir and interactions at the wild-domestic interface. Samples were collected from migratory birds in Poyang Lake, Jiangxi Province, PR China during the routine bird ring survey in 2014-16. Phylogenetic and coalescent analyses were conducted to uncover the evolutionary relationship among viruses circulating in wild birds. Here, we report the potential origin and phylogenetic diversity of H5N6 viruses isolated from wild birds in Poyang Lake. Sequence analyses indicated that Jiangxi H5N6 viruses most likely evolved from Eurasian-derived H5Nx and H6N6 viruses through multiple reassortment events. Crucially, the diversity of the HA gene implies that these Jiangxi H5N6 viruses have diverged into two primary clades - clade 2.3.4.4 and clade 2.3.2.1 c. Phylogenetic analysis revealed two independent pathways of reassortment during 2014-16 that might have facilitated the generation of emerging variants within wild bird populations as well as inter-species infections. Our findings contribute to our understanding of the genetic diversification of H5N6 viruses in the wild bird population. These results highlight the necessity of large-scale surveillance of wild birds in the Poyang Lake area to address the threat of regional epizootic epidemics and attendant pandemics.

Avian influenza overview August - November2019

Between 16 August and 15 November 2019, one low pathogenic avian influenza (LPAI) A(H5) outbreak in poultry in France was reported in Europe. Genetic characterisation reveals that the virusclusterswith Eurasian LPAI viruses. No highly pathogenic avian influenza (HPAI) outbreaks in birds were notified in Europe in the relevant period for this report. HPAI A(H5N6) viruswas identified in chickens in Nigeria, this isthe first report of HPAI A(H5N6) from the African continent.FewerHPAI outbreaks in Asia and Africa were reported during the time period for this report compared with the previous reporting period. Apart from the long‐term epidemic of HPAI A(H5N2)in Taiwan, only six HPAI outbreakswere reported in domestic birds from Nepal, South Africa and Taiwan. Furthermore, no HPAI detections fromwild birds were reported worldwide in the relevant time period forthis report.Even if the risk of incursion of HPAI from wild birds into poultryestablishments in Europe is currently assessed as low, it is important to maintain passive surveillance activities. The focus should be on wild bird species that are in the revised list of target species in order to detect any incursion of HPAI virus early and initiate a warning.Despite the decrease in the number of avian influenza outbreaks over recent months, it is important to maintain a high alert level andhigh standard of biosecurity onpoultry establishments.In Europe, no human infections due toHPAI viruses detected in wild bird or poultry outbreaks, have been reported. The risk of zoonotic transmission to the general public in Europe is considered to be very low.