Survey of low pathogenic avian influenza viruses in live poultry markets in Guangxi Province, Southern China, 2016–2019

Low pathogenic avian influenza viruses (LPAIVs) have been widespread in poultry and wild birds throughout the world for many decades. LPAIV infections are usually asymptomatic or cause subclinical symptoms. However, the genetic reassortment of LPAIVs may generate novel viruses with increased virulence and cross-species transmission, posing potential risks to public health. To evaluate the epidemic potential and infection landscape of LPAIVs in Guangxi Province, China, we collected and analyzed throat and cloacal swab samples from chickens, ducks and geese from the live poultry markets on a regular basis from 2016 to 2019. Among the 7,567 samples, 974 (12.87%) were LPAIVs-positive, with 890 single and 84 mixed infections. Higher yearly isolation rates were observed in 2017 and 2018. Additionally, geese had the highest isolation rate, followed by ducks and chickens. Seasonally, spring had the highest isolation rate. Subtype H3, H4, H6 and H9 viruses were detected over prolonged periods, while H1 and H11 viruses were detected transiently. The predominant subtypes in chickens, ducks and geese were H9, H3, and H6, respectively. The 84 mixed infection samples contained 22 combinations. Most mixed infections involved two subtypes, with H3 + H4 as the most common combination. Our study provides important epidemiological data regarding the isolation rates, distributions of prevalent subtypes and mixed infections of LPAIVs. These results will improve our knowledge and ability to control epidemics, guide disease management strategies and provide early awareness of newly emerged AIV reassortants with pandemic potential.

Transcriptomics of chicken cecal tonsils and intestine after infection with low pathogenic avian influenza virus H9N2

Influenza viruses cause severe respiratory infections in humans and birds, triggering global health concerns and economic burden. Influenza infection is a dynamic process involving complex biological host responses. The objective of this study was to illustrate global biological processes in ileum and cecal tonsils at early time points after chickens were infected with low pathogenic avian influenza virus (LPAIV) H9N2 through transcriptome analysis. Total RNA isolated from ileum and cecal tonsils of non-infected and infected layers at 12-, 24- and 72-h post-infection (hpi) was used for mRNA sequencing analyses to characterize differentially expressed genes and overrepresented pathways. Statistical analysis highlighted transcriptomic signatures significantly occurring 24 and 72 hpi, but not earlier at 12 hpi. Interferon (IFN)-inducible and IFN-stimulated gene (ISG) expression was increased, followed by continued expression of various heat-shock proteins (HSP), including HSP60, HSP70, HSP90 and HSP110. Some upregulated genes involved in innate antiviral responses included DDX60, MX1, RSAD2 and CMPK2. The ISG15 antiviral mechanism pathway was highly enriched in ileum and cecal tonsils at 24 hpi. Overall, most affected pathways were related to interferon production and the heat-shock response. Research on these candidate genes and pathways is warranted to decipher underlying mechanisms of immunity against LPAIV in chickens.

Opposite outcomes of the within-host competition between highly and low pathogenic H5N8 avian influenza viruses in chickens compared to ducks

Highly pathogenic avian influenza viruses (HPAIV) emerge from low pathogenic avian influenza viruses (LPAIV) through the introduction of basic amino acids at the hemagglutinin (HA) cleavage site. Following viral evolution, the newly formed HPAIV likely represents a minority variant within the index host, predominantly infected with the LPAIV precursor. Using reverse-genetics engineered H5N8 viruses differing solely at the HA cleavage, we tested the hypothesis that the interaction between the minority HPAIV and the majority LPAIV could modulate the risk of HPAIV emergence and that the nature of the interaction could depend on the host species. In chickens, we observed that the H5N8 LP increased H5N8 HP replication and pathogenesis. By contrast, the H5N8 LP antagonized H5N8 HP replication and pathogenesis in ducks. Ducks mounted a more potent antiviral innate immune response than chickens against the H5N8 LP , which correlated with H5N8 HP inhibition. These data provide experimental evidence that HPAIV may be more likely to emerge in chickens than in ducks and underscore the importance of within-host viral variants interactions in viral evolution. IMPORTANCE Highly pathogenic avian influenza viruses represent a threat to poultry production systems and to human health because of their impact on food security and because of their zoonotic potential. It is therefore crucial to better understand how these viruses emerge. Using a within-host competition model between highly and low pathogenic avian influenza viruses, we provide evidence that highly pathogenic avian influenza viruses could be more likely to emerge in chickens than in ducks. These results have important implications for highly pathogenic avian influenza virus emergence prevention and they underscore the importance of within-host viral variants interactions in virus evolution.

Laporan Kasus Avian Influenza di Dusun Cabean, Kelurahan Mangunsari, Kecamatan Sidomukti, Kota Salatiga Tahun 2019

Virus Avian Influenza (AI) dibedakan menjadi Low Pathogenic Avian Influenza (LPAI) dan High Pathogenic Avian Influenza (HPAI) dimana pada HPAI ditunjukkan dengan tingkat kematian unggas yang mencapai 100% dalam waktu yang singkat. Tujuan dari penelitian terhadap kematian unggas di Cabean, kelurahan Mangunsari, Kecamatan Sidomukti, Kota Salatiga adalah untuk mengidentifikasi penyebab kematian dan menentukan tindakan pengendalian. Observasi dilakukan pada tanggal 29 Juli 2019 hingga 3 Agustus 2019 dan analisis data dilakukan secara deskriptif. Informasi kematian mendadak pada unggas dilaporkan pemilik pada 29 Juli 2019. Dalam satu minggu kematian ayam kampung mencapai 38,75%, itik manila (entok) mencapai 90% dan angsa mencapai 100%. Dari hasil pemeriksaan berdasarkan informasi, nekropsi, rapid test dan laboratorium, dapat disimpulkan bahwa kematian mendadak pada unggas yang terjadi di Cabean disebabkan oleh virus Avian Influenza. Hasil investigasi diharapkan mampu memberikan kejelasan penyebab kematian unggas dan pemahaman kepada masyarakat terutama peternak unggas mengenai virus Avian Influenza, tindak pencegahan dan penanggulangannya.

Emergence of a Novel Reassortant H5N3 Avian Influenza Virus in Korean Mallard Ducks in 2018

<b><i>Introduction:</i></b> The avian influenza (AI) virus causes a highly contagious disease which is common in wild and domestic birds and sporadic in humans. Mutations and genetic reassortments among the 8 negative-sense RNA segments of the viral genome alter its pathogenic potential, demanding well-targeted, active surveillance for infection control. <b><i>Methods:</i></b> Wild duck fecal samples were collected during the 2018 bird health annual surveillance in South Korea for tracking variations of the AI virus. One low-pathogenic avian influenza H5N3 reassortment virus (A/mallard duck/South Korea/KNU18-91/2018 [H5N3]) was isolated and genomically characterized by phylogenetic and molecular analyses in this study. <b><i>Results:</i></b> It was devoid of polybasic amino acids at the hemagglutinin (HA) cleavage site and exhibited a stalk region without deletion in the neuraminidase (<i>NA</i>) gene and NA inhibitor resistance-linked E/D627K/N and D701N marker mutations in the <i>PB2</i> gene, suggesting its low-pathogenic AI. It showed a potential of a reassortment where only <i>HA</i> originated from the H5N3 poultry virus of China and other genes were derived from Mongolia. In phylogenetic analysis, HA was different from that of the isolate of H5N3 in Korea, 2015. In addition, this novel virus showed adaptation in Madin-Darby canine kidney cells, with 8.05 ± 0.14 log10 50% tissue culture infectious dose (TCID50) /mL at 36 h postinfection. However, it could not replicate in mice well, showing positive growth at 3 days postinfection (dpi) (2.1 ± 0.13 log10 TCID50/mL) but not at 6 dpi. <b><i>Conclusions:</i></b> The HA antigenic relationship of A/mallard duck/South Korea/KNU18-91/2018 (H5N3) showed differences toward one of the old low-pathogenic H5N3 viruses in Korea. These results indicated that a novel reassortment low-pathogenic avian influenza H5N3 subtype virus emerged in South Korea in 2018 via novel multiple reassortments with Eurasian viruses, rather than one of old Korean H5N3 strains.

Comparative testing of vaccines based on viruses of genetic lineages G1 and Y280 for their potency against low pathogenic avian influenza H9N2

Due to the genetic diversity of low pathogenic avian influenza (LPAI) viruses of subtype H9N2, it deemed appropriate to study the potency of the vaccines based on the antigens of strains А/chicken/Amursky/03/12 and A/chicken/Chelyabinsk/314-1/20 that represent currently circulating in the Russian Federation genetic lineages Y280 and G1, respectively. While low pathogenicity of the agent does not allow demonstrating the vaccine protective properties by the direct methods generally used for potency assessment (e.g. morbidity and mortality), the indirect methods were used: determination of antigenic relatedness of the strains, level of the postvaccinal homologous and heterologous humoral immunity, analysis of the virus genome synthesis inhibition (reduction) in vaccinated birds following their challenge. The strains used in the vaccines were determined to have some antigenic differences, which were demonstrated in the hemagglutination inhibition (HI) assay during control of the postvaccinal immunity in birds. Both vaccines generally induced strong humoral immunity in vaccinated birds (9–10 log2 determined using HI assay) with some difference in the levels of the immune response following the use of homologous or heterologous antigens. It was also reliably determined that homologous immunity facilitated more expressed inhibition of the virus reproduction after the challenge. The level of inhibition (reduction) of the virulent LPAI virus genome synthesis in vaccinated birds following their challenge with H9N2 virus of genetic lineage G1 was higher in birds following homologous vaccination, while the time periods of the genome detection in the biomaterial samples were the same. It was demonstrated that due to antigenic and immunogenic differences between LPAI H9N2 strains, use of both antigenic components in the inactivated vaccines is appropriate.