Antigenic and molecular characterization of avian influenza A(H9N2) viruses, Bangladesh

Mutual antagonism of mouse-adaptation mutations in HA and PA proteins on H9N2 virus replication

Avian H9N2 viruses have wide host range among the influenza A viruses. However, knowledge of H9N2 mammalian adaptation is limited. To explore the molecular basis of the adaptation to mammals, we performed serial lung passaging of the H9N2 strain A/chicken/Hunan/8.27 YYGK3W3-OC/2018 (3W3) in mice and identified six mutations in the hemagglutinin (HA) and polymerase acidic (PA) proteins. Mutations L226Q, T511I, and A528V of HA were responsible for enhanced pathogenicity and viral replication in mice; notably, HA-L226Q was the key determinant. Mutations T97I, I545V, and S594G of PA contributed to enhanced polymerase activity in mammalian cells and increased viral replication levels in vitro and in vivo. PA-T97I increased viral polymerase activity by accelerating the viral polymerase complex assembly. Our findings revealed that the viral replication was affected by the presence of PA-97I and/or PA-545V in combination with a triple-point HA mutation. Furthermore, the double- and triple-point PA mutations demonstrated antagonistic effect on viral replication when combined with HA-226Q. Notably, any combination of PA mutations, along with double-point HA mutations, resulted in antagonistic effect on viral replication. We also observed antagonism in viral replication between PA-545V and PA-97I, as well as between HA-528V and PA-545V. Our findings demonstrated that several antagonistic mutations in HA and PA proteins affect viral replication, which may contribute to the H9N2 virus adaptation to mice and mammalian cells. These findings can potentially contribute to the monitoring of H9N2 field strains for assessing their potential risk in mammals.

Antigenic mapping of the hemagglutinin of the H9 subtype influenza A viruses using sera from Japanese quail (Coturnix c. japonica)

IMPORTANCE

Determining the relevant amino acids involved in antigenic drift on the surface protein hemagglutinin (HA) is critical to understand influenza virus evolution and efficient assessment of vaccine strains relative to current circulating strains. We used antigenic cartography to generate an antigenic map of the H9 hemagglutinin (HA) using sera produced in one of the most relevant minor poultry species, Japanese quail. Key antigenic positions were identified and tested to confirm their impact on the antigenic profile. This work provides a better understanding of the antigenic diversity of the H9 HA as it relates to reactivity to quail sera and will facilitate a rational approach for selecting more efficacious vaccines against poultry-origin H9 influenza viruses in minor poultry species.

KRT10 plays an important role in the release of viral genome from endosomes during H9N2 subtype AIV replication in HeLa cells

The infection and replication of avian influenza virus (AIV) in host cells is a complex biological process that involves the transport of viral genes through the host cell's transport systems. Actin, microtubules and vimentin are known to facilitate transport of endosomes to the perinuclear region, but the biological role of Keratin, another intermediate filament, in viral transport during AIV replication is not well understood. In this study, the viral NS2 protein was used as the target protein to identify the potential interacting proteins following GST-Pulldown method and protein mass spectrometry. It was discovered that Keratin10 interacted with NS2. Subsequently, it was found AIV infection did not affect the gene level or protein level of keratin10 in HeLa cells, but when Keratin10 was knocked down, the expressions of viral NP mRNA and protein were reduced, and the generation of offspring virus also was also decreased. Furthermore, in early viral infection, Keratin10 could aggregate and co-localize with NP proteins, suggesting that Keratin10 might be connected to early viral transport. Additionally, it was demonstrated that Keratin10 co-localized with Lamp1 and that AIV particles were trapped in late endosomes/Lysosomes after Keratin10 was knocked down. Finally, it was discovered that the knocking down Keratin10 in HeLa cells led to an increase in the acidic pH of endosomes and lysosomes, which prevented AIV from undergoing fusion and uncoating, and then inhibited the process of the viral infection. Overall, the results suggested that Keratin10 might play the critical role in the release of vRNPs from LEs/Ls and can affect the generation of offspring virus. The study provides the novel insights into the role of Keratin10 in the process of AIV infection and transmission, which may have implications for developing new strategies to against AIV infections.

Experimental Pathogenicity of H9N2 Avian Influenza Viruses Harboring a Tri-Basic Hemagglutinin Cleavage Site in Sonali and Broiler Chickens

Low-pathogenic avian influenza (LPAI) H9N2 virus is endemic in Bangladesh, causing huge economic losses in the poultry industry. Although a considerable number of Bangladeshi LPAI H9N2 viruses have been molecularly characterized, there is inadequate information on the pathogenicity of H9N2 viruses in commercial poultry. In this study, circulating LPAI H9N2 viruses from recent field outbreaks were characterized, and their pathogenicity in commercial Sonali (crossbred) and broiler chickens was assessed. Phylogenetic analysis of currently circulating field viruses based on the hemagglutinin (HA) and neuraminidase (NA) gene sequences revealed continuous circulation of G1 lineages containing the tri-basic hemagglutinin cleavage site (HACS) motif (PAKSKR*GLF) at the HA protein. Both the LPAI susceptible Sonali and broiler chickens were infected with selected H9N2 isolates A/chicken/Bangladesh/2458-LT2/2020 or A/chicken/Bangladesh/2465-LT56/2021 using intranasal (100 µL) and intraocular (100 µL) routes with a dose of 10⁶ EID₅₀/_mL. Infected groups (LT_2-So1 and LT_56-So2; LT_2-Br1 and LT_56-Br2) revealed no mortality or clinical signs. However, at gross and histopathological investigation, the trachea, lungs, and intestine of the LT_2-So1 and LT_56-So2 groups displayed mild to moderate hemorrhages, congestion, and inflammation at different dpi. The LT 2-Br1 and LT 56-Br2 broiler groups showed nearly identical changes in the trachea, lungs, and intestine at various dpi, indicating no influence on pathogenicity in the two commercial bird species under study. Overall, the prominent lesions were observed up to 7 dpi and started to disappear at 10 dpi. The H9N2 viruses predominantly replicated in the respiratory tract, and higher titers of virus were shed through the oropharyngeal route than the cloacal route. Finally, this study demonstrated the continuous evolution of tri-basic HACS containing H9N2 viruses in Bangladesh with a low-pathogenic phenotype causing mild to moderate tracheitis, pneumonia, and enteritis in Sonali and commercial broiler chickens.

Epidemiology and molecular characterization of avian influenza virus in backyard poultry of Chattogram, Bangladesh

Ducks, the natural reservoir of avian influenza virus (AIV), act as reassortment vessels for HPAI and low pathogenic avian influenza (LPAI) virus for domestic and wild bird species. In Bangladesh, earlier research was mainly focused on AIV in commercial poultry and live bird markets, where there is scanty literature reported on AIV in apparently healthy backyard poultry at the household level. The present cross-sectional study was carried out to reveal the genomic epidemiology of AIV of backyard poultry in coastal (Anowara) and plain land (Rangunia) areas of Bangladesh. We randomly selected a total of 292 households' poultry (having both chicken and duck) for sampling. We administered structured pre-tested questionnaires to farmers through direct interviews. We tested cloacal samples from birds for the matrix gene (M gene) followed by H5 and H9 subtypes using real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). All AIV-positive samples were subjected to four-gene segment sequencing (M, PB1, HA, and NA gene). We found that the prevalence of AIV RNA at the household level was 6.2% (n = 18; N = 292), whereas duck and chicken prevalence was 3.6% and 3.2%, respectively. Prevalence varied with season, ranging from 3.1% in the summer to 8.2% in the winter. The prevalence of subtypes H5 and H9 in backyard poultry was 2.7% and 3.3%, respectively. The phylogenetic analysis of M, HA, NA, and PB1 genes revealed intra-genomic similarity, and they are closely related to previously reported AIV strains in Bangladesh and Southeast Asia. The findings indicate that H5 and H9 subtypes of AIV are circulating in the backyard poultry with or without clinical symptoms. Moreover, we revealed the circulation of 2.3.2.1a (new) clade among the chicken and duck population without occurring outbreak which might be due to vaccination. In addition to routine surveillance, molecular epidemiology of AIV will assist to gain a clear understanding of the genomic evolution of the AIV virus in the backyard poultry rearing system, thereby facilitating the implementation of effective preventive measures to control infection and prevent the potential spillover to humans.

Antigenic Evolution Characteristics and Immunological Evaluation of H9N2 Avian Influenza Viruses from 1994–2019 in China

The H9N2 subtype avian influenza viruses (AIVs) have been circulating in China for more than 20 years, attracting more and more attention due to the potential threat of them. At present, vaccination is a common prevention and control strategy in poultry farms, but as virus antigenicity evolves, the immune protection efficiency of vaccines has constantly been challenged. In this study, we downloaded the hemagglutinin (HA) protein sequences of the H9N2 subtype AIVs from 1994 to 2019 in China—with a total of 5138 sequences. The above sequences were analyzed in terms of time and space, and it was found that h9.4.2.5 was the most popular in various regions of China. Furthermore, the prevalence of H9N2 subtype AIVs in China around 2006 was different. The domestic epidemic branch was relatively diversified from 1994 to 2006. After 2006, the epidemic branch each year was h9.4.2.5. We compared the sequences around 2006 as a whole and screened out 15 different amino acid positions. Based on the HA protein of A/chicken/Guangxi/55/2005 (GX55), the abovementioned amino acid mutations were completed. According to the 12-plasmid reverse genetic system, the rescue of the mutant virus was completed using A/PuertoRico/8/1934 (H1N1) (PR8) as the backbone. The cross hemagglutination inhibition test showed that these mutant sites could transform the parental strain from the old to the new antigenic region. Animal experiments indicated that the mutant virus provided significant protection against the virus from the new antigenic region. This study revealed the antigenic evolution of H9N2 subtype AIVs in China. At the same time, it provided an experimental basis for the development of new vaccines.

Household Bird Ownership is Associated with Respiratory Illness among Young Children in Urban Bangladesh (CHoBI7 Program)

There is limited evidence on the association between animal ownership and respiratory illness among young children in low- and middle-income countries. In this study, we examined the association between animal ownership and respiratory illness among children younger than 5 years of age enrolled in a prospective cohort study in urban Bangladesh. This prospective cohort study enrolled 884 participants younger than 5 years of age in Dhaka, Bangladesh. At baseline, trained research assistants administered caregivers of children younger than 5 years of age a questionnaire on household animal ownership. Animal ownership was defined as owning chickens, birds other than chickens, cats, and dogs. Respiratory surveillance was conducted monthly for children based on caregiver-reported coughing, rapid breathing, and difficulty breathing in the past 2 weeks during the 12-month study period. At baseline, 48% of children (424 of 884) had reports of coughing, 5% (40 of 884) had difficulty breathing, 3% (25 of 884) had rapid breathing, and 49% (431 of 884) had reports of any of these three respiratory symptoms. Seventeen percent of children (151 of 884) resided in a household that owned an animal. Children residing in households reporting bird ownership had a significantly greater odds of coughing (odds ratio, 1.14; 95% CI, 1.02-1.28) and any of the three respiratory symptoms in the past 2 weeks (odds ratio, 1.14; 95% CI, 1.02-1.28). Household bird ownership was associated with respiratory illness in young children. These findings suggest that interventions aiming to reduce young children's exposure to domestic animals should extend to include birds other than chickens.

Semi-Scavenging Poultry as Carriers of Avian Influenza Genes

Ducks are the natural reservoir of influenza A virus and the central host for the avian influenza virus (AIV) subtype H5N1, which is highly pathogenic. Semi-scavenging domestic ducks allow for the reemergence of new influenza subtypes which could be transmitted to humans. We collected 844 cloacal swabs from semi-scavenging ducks inhabiting seven migratory bird sanctuaries of Bangladesh for the molecular detection of avian influenza genes. We detected the matrix gene (M gene) using real-time RT-PCR (RT-qPCR). Subtyping of the AIV-positive samples was performed by RT-qPCR specific for H5, H7, and H9 genes. Out of 844 samples, 21 (2.488%) were positive for AIV. Subtyping of AIV positive samples (n = 21) revealed that nine samples (42.85%) were positive for the H9 subtype, five (23.80%) were positive for H5, and seven (33.33%) were negative for the three genes (H5, H7, and H9). We detected the same genes after propagating the virus in embryonated chicken eggs from positive samples. Semi-scavenging ducks could act as carriers of pathogenic AIV, including the less pathogenic H9 subtype. This can enhance the pathogenicity of the virus in ducks by reassortment. The large dataset presented in our study from seven areas should trigger further studies on AIV prevalence and ecology.

Distinct but connected avian influenza virus activities in wetlands and live poultry markets in Bangladesh, 2018-2019

From April 2018 to October 2019, we continued active surveillance for influenza viruses in Bangladeshi live poultry markets (LPMs) and in Tanguar Haor, a wetland region of Bangladesh where domestic ducks have frequent contact with migratory birds. The predominant virus subtypes circulating in the LPMs were low pathogenic avian influenza (LPAI) H9N2 and clade 2.3.2.1a highly pathogenic avian influenza (HPAI) H5N1 viruses of the H5N1-R1 genotype, like those found in previous years. Viruses of the H5N1-R2 genotype, which were previously reported as co-circulating with H5N1-R1 genotype viruses in LPM, were not detected. In addition to H9N2 viruses, which were primarily found in chicken and quail, H2N2, H3N8 and H11N3 LPAI viruses were detected in LPMs, exclusively in ducks. Viruses in domestic ducks and/or wild birds in Tanguar Haor were more diverse, with H1N1, H4N6, H7N1, H7N3, H7N4, H7N6, H8N4, H10N3, H10N4 and H11N3 detected. Phylogenetic analyses of these LPAI viruses suggested that some were new to Bangladesh (H2N2, H7N6, H8N4, H10N3 and H10N4), likely introduced by migratory birds of the Central Asian flyway. Our results show a complex dynamic of viral evolution and diversity in Bangladesh based on factors such as host populations and geography. The LPM environment was characterised by maintenance of viruses with demonstrated zoonotic potential and H5N1 genotype turnover. The wetland environment was characterised by greater viral gene pool diversity but a lower overall influenza virus detection rate. The genetic similarity of H11N3 viruses in both environments demonstrates that LPM and wetlands are connected despite their having distinct influenza ecologies.

Detection of a Novel Reassortant H9N9 Avian Influenza Virus in Free-Range Ducks in Bangladesh

Wild aquatic birds are the primary natural reservoir for influenza A viruses (IAVs). In this study, an A(H9N9) influenza A virus (A/duck/Bangladesh/44493/2020) was identified via routine surveillance in free-range domestic ducks in Bangladesh. Phylogenetic analysis of hemagglutinin showed that the H9N9 virus belonged to the Y439-like lineage. The HA gene had the highest nucleotide identity to A/Bean Goose (Anser fabalis)/South Korea/KNU 2019-16/2019 (H9N2). The other seven gene segments clustered within the Eurasian lineage.

Improved pathogenicity of H9N2 subtype of avian influenza virus induced by mutations occurred after serial adaptations in mice

H9N2 subtype, a low pathogenic avian influenza virus, is emerging as a major causative agent circulating poultry workplaces across China and other Asian countries. Increasing case number of interspecies transmissions to mammals reported recently provoked a great concern about its risks inducing global pandemics. In an attempt to understand the underlying mechanism of how the H9N2 virus disrupts the interspecies segregation to transmit to mammals. A mutant H9N2 strain was obtained by passaging the wildtype H9N2 A/chicken/Hong Kong/G9/1997 eight times from lung to lung in BALB/c mice. Our finding revealed that mice manifested severe clinical symptoms including losses of body weight, pathological damages in pulmonary sites and all died within two weeks after infected with the mutated H9N2, whereas all mice survived upon infected with wildtype strain in comparison, which suggested increased pathogenicity of the mutant strain. In addition, mice showed enhanced levels of proinflammatory cytokines in sera, including IL-6, TNF-α and IL-1β compared to those subjected to wildtype viral infections. Sequence analysis showed that five amino acid substitutions occurred at PB2₆₂₇, HA_87, HA₂₃₄, NP₃₈₇ and M₁₅₆, and a deletion mutation happened in the M gene (M₁₅₇). Of these mutations, PB2 E627K played key roles in modulating lethality in mice. Taken together, the mutant H9N2 strain obtained by serial passaging of its wildtype in mice significantly increased its virulence leading to death of mice, which might be associated the accumulated mutations occurred on its genome.

Surveillance on respiratory diseases reveals enzootic circulation of both H5 and H9 avian influenza viruses in small-scale commercial layer farms of Bangladesh

Poultry production in Bangladesh has been experiencing H5N1 highly pathogenic avian influenza (HPAI) and H9N2 low pathogenic avian influenza (LPAI) for the last 14 years. Vaccination of chickens against H5 HPAI is in practice since the end of 2012. Subsequently, the official reporting of HPAI outbreaks gradually decreased. However, the true extent of circulation of avian influenza virus (AIV) in commercial poultry production is not clear. To explore this, we conducted active surveillance in 422 small-scale commercial layer farms in 20 villages of Mymensingh and Tangail districts of Bangladesh during 2017 and 2018 for the presence of diseases with respiratory signs. A total of 88 farms with respiratory disease problems were identified and investigated during the surveillance. In addition, 22 small-scale commercial layer farms in the neighbouring areas with respiratory disease problem were also investigated on request from the farmers. Pooled samples of oropharyngeal swabs from live birds or respiratory tissues from dead birds of the farm suffering from respiratory disease problem were tested for molecular detection of avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum and Avibacterium paragallinarum. A total of 110 farms (88 in the surveillance site and 22 in the neighbouring region) were investigated, and one or more respiratory pathogens were detected from 89 farms. AIV was detected in 57 farms often concurrently with other pathogens. Among these 57 farms, H5, H9, both H5 and H9 or non-H5 and non-H9 AIV were detected in 28, 9, 13 or 7 farms, respectively. Birds of most of the H5 AIV-positive farms did not present typical clinical signs or high mortality. Twenty such farms were observed longitudinally, which had only 1.05%-5.50% mortality but a marked drop in egg production. This widespread circulation of H5 AIV along with H9 AIV and other pathogens in small-scale commercial layer farms, often with low mortality, reaffirms the enzootic circulation of AIV in Bangladesh, which may escape syndromic surveillance focused on unusual mortality only. To reduce public health risks, strengthening of the control programme with comprehensive vaccination, enhanced biosecurity, improved surveillance and outbreak response is suggested.

Genetic Evolution Characteristics of Genotype G57 Virus, A Dominant Genotype of H9N2 Avian Influenza Virus

This study aimed to investigate the genetic evolution of the H9N2 avian influenza virus (AIV). Whole genome phylogenetic trees were constructed based on 306 H9N2 avian influenza strains collected in China from 2014 to 2019. The results showed that eight gene sequences were clustered separately according to their dominant clades, and a total of 10 genotypes were identified (seven of which were novel types). Among them, G57 genotype was confirmed as the most prevalent genotype with a frequency of 94%. In China, the G57 genotype of H9N2 first emerged in 2007, and then became the most common genotype in 2013. Therefore, the nucleotide substitution rates of G57 genotype in HA and NA genes collected from 2007 to 2019 were estimated, and the positive selection pressure sites in the same data set were measured. Taking 2013 as the boundary, the time period was divided into two periods: 2007-2012 and 2013-2019. From 2007 to 2012, multiple genotypes coexisted and could bear the pressures from both nature and environment; while G57 genotype was still in the adaptation stage, subjected to less selection pressure and in the process of slow evolution. However, from 2013 to 2019, G57 became the dominant genotype, and most of the external pressure reacted on it. Moreover, G57 genotype showed better adaptability than other genotypes. From 2013 to 2019, the nucleotide substitution rates of the HA gene were increased, and the positive selection pressures on HA and NA genes were stronger compared to those from 2007 to 2012. To sum up, the absolutely dominant G57 genotype exhibited a relatively constant genotype frequency and experienced adaptive evolution and natural selection simultaneously during the monitoring period. Therefore, urgent attention and diligent surveillance of H9N2 avian influenza virus are becoming increasingly important.

Continued Evolution of H5Nx Avian Influenza Viruses in Bangladeshi Live Poultry Markets: Pathogenic Potential in Poultry and Mammalian Models

The genesis of novel influenza viruses through reassortment poses a continuing risk to public health. This is of particular concern in Bangladesh, where highly pathogenic avian influenza viruses of the A(H5N1) subtype are endemic and cocirculate with other influenza viruses. Active surveillance of avian influenza viruses in Bangladeshi live poultry markets detected three A(H5) genotypes, designated H5N1-R1, H5N1-R2, and H5N2-R3, that arose from reassortment of A(H5N1) clade 2.3.2.1a viruses. The H5N1-R1 and H5N1-R2 viruses contained HA, NA, and M genes from the A(H5N1) clade 2.3.2.1a viruses and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. H5N2-R3 viruses contained the HA gene from circulating A(H5N1) clade 2.3.2.1a viruses, NA and M genes from concurrently circulating A(H9N2) influenza viruses, and PB2, PB1, PA, NP, and NS genes from other Eurasian influenza viruses. Representative viruses of all three genotypes and a parental clade 2.3.2.1a strain (H5N1-R0) infected and replicated in mice without prior adaptation; the H5N2-R3 virus replicated to the highest titers in the lung. All viruses efficiently infected and killed chickens. All viruses replicated in inoculated ferrets, but no airborne transmission was detected, and only H5N2-R3 showed limited direct-contact transmission. Our findings demonstrate that although the A(H5N1) viruses circulating in Bangladesh have the capacity to infect and replicate in mammals, they show very limited capacity for transmission. However, reassortment does generate viruses of distinct phenotypes.IMPORTANCE Highly pathogenic avian influenza A(H5N1) viruses have circulated continuously in Bangladesh since 2007, and active surveillance has detected viral evolution driven by mutation and reassortment. Recently, three genetically distinct A(H5N1) reassortant viruses were detected in live poultry markets in Bangladesh. Currently, we cannot assign pandemic risk by only sequencing viruses; it must be conducted empirically. We found that the H5Nx highly pathogenic avian influenza viruses exhibited high virulence in mice and chickens, and one virus had limited capacity to transmit between ferrets, a property considered consistent with a higher zoonotic risk.

Controlling Avian Influenza Virus in Bangladesh: Challenges and Recommendations

Avian influenza virus (AIV) remains a huge challenge for poultry production with negative repercussions for micro- and macro-economy and public health in Bangladesh. High (HP) H5N1 and low pathogenicity (LP) H9N2 AIV are currently endemic in poultry, and both have been reported to infect humans sporadically. Multiple virus introductions of different clades of HPAIV H5N1, reassorted genotypes, and on-going diversification of LPAIV H9N2 create a highly volatile virological environment which potentially implicates increased virulence, adaptation to new host species, and subsequent zoonotic transmission. Allotropy of poultry rearing systems and supply chains further increase the risk of virus spreading, which leads to human exposure and fosters the emergence of new potentially pre-pandemic virus strains. Here, we review the epidemiology, focusing on (i) risk factors for virus spreading, (ii) viral genetic evolution, and (iii) options for AIV control in Bangladesh. It is concluded that improved control strategies would profit from the integration of various intervention tools, including effective vaccination, enhanced biosecurity practice, and improved awareness of producers and traders, although widespread household poultry rearing significantly interferes with any such strategies. Nevertheless, continuous surveillance associated with rapid diagnosis and thorough virus characterization is the basis of such strategies.

H9 Influenza Viruses: An Emerging Challenge

Influenza A viruses (IAVs) of the H9 subtype are enzootic in Asia, the Middle East, and parts of North and Central Africa, where they cause significant economic losses to the poultry industry. Of note, some strains of H9N2 viruses have been linked to zoonotic episodes of mild respiratory diseases. Because of the threat posed by H9N2 viruses to poultry and human health, these viruses are considered of pandemic concern by the World Health Organization (WHO). H9N2 IAVs continue to diversify into multiple antigenically and phylogenetically distinct lineages that can further promote the emergence of strains with pandemic potential. Somewhat neglected compared with the H5 and H7 subtypes, there are numerous indicators that H9N2 viruses could be involved directly or indirectly in the emergence of the next influenza pandemic. The goal of this work is to discuss the state of knowledge on H9N2 IAVs and to provide an update on the contemporary global situation.

Recombinant Lactococcus Lactis Expressing M1-HA2 Fusion Protein Provides Protective Mucosal Immunity Against H9N2 Avian Influenza Virus in Chickens

H9N2 subtype low pathogenicity avian influenza virus (LPAIV) is distributed worldwide and causes enormous economic losses in the poultry industry. Despite immunization of almost all chickens with inactivated vaccines, the disease still remains widespread. We speculated that improving mucosal or cellular immune responses could contribute to improved control of H9N2 viruses. In this study, we constructed a novel Lactococcus lactis (L. lactis) strain expressing a recombinant fusion protein consisting of the M1 and HA2 proteins derived from an antigenically conserved endemic H9N2 virus strain. The M1-HA2 fusion protein was cloned downstream of a gene encoding a secretory peptide, and we subsequently confirmed that the fusion protein was secreted from L. lactis by Western blotting. We assessed the immunogenicity and protective effects of this recombinant L. lactis strain. Eighty 1-day-old chickens were divided into four groups, and the experimental groups were orally vaccinated twice with the recombinant L. lactis strain. Fecal and intestinal samples, sera, and bronchoalveolar lavage fluid were collected at 7, 14, and 21 days post-vaccination (dpv). Chickens vaccinated with the recombinant L. lactis strain showed significantly increased levels of serum antibodies, T cell-mediated immune responses, and mucosal secretory IgA (SIgA). Following challenge with H9N2 virus at 21 dpv, chickens vaccinated with the recombinant L. lactis strain showed decreased weight loss, lower viral titers in the lung, and reduced lung pathological damage. In summary, our results demonstrated that a recombinant L. lactis strain expressing an H9N2 M1-HA2 fusion protein could induce protective mucosal and systemic immunity. This oral vaccine is H9N2 virus-specific and represents a significant design improvement compared with previous studies. Our study provides a theoretical basis for improving mucosal immune responses to prevent and control H9N2 virus infection.

Avian influenza viruses in humans: lessons from past outbreaks

BACKGROUND

Human infections with avian influenza viruses (AIV) represent a persistent public health threat. The principal risk factor governing human infection with AIV is from direct contact with infected poultry and is primarily observed in Asia and Egypt where live-bird markets are common.

AREAS OF AGREEMENT

Changing patterns of virus transmission and a lack of obvious disease manifestations in avian species hampers early detection and efficient control of potentially zoonotic AIV.

AREAS OF CONTROVERSY

Despite extensive studies on biological and environmental risk factors, the exact conditions required for cross-species transmission from avian species to humans remain largely unknown.

GROWING POINTS

The development of a universal ('across-subtype') influenza vaccine and effective antiviral therapeutics are a priority.

AREAS TIMELY FOR DEVELOPING RESEARCH

Sustained virus surveillance and collection of ecological and physiological parameters from birds in different environments is required to better understand influenza virus ecology and identify risk factors for human infection.

Laboratory-Confirmed Avian Influenza A(H9N2) Virus Infection, India, 2019

A 17-month-old boy in India with severe acute respiratory infection was laboratory confirmed to have avian influenza A(H9N2) virus infection. Complete genome analysis of the strain indicated a mixed lineage of G1 and H7N3. The strain also was found to be susceptible to adamantanes and neuraminidase inhibitors.

First report of human infection with avian influenza A(H9N2) virus in Oman: The need for a One Health approach

Following the detection of the first human case of avian influenza A subtype H9N2 in 1998, more than 40 cases were diagnosed worldwide. However, the spread of the virus has been more remarkable and significant in global poultry populations, causing notable economic losses despite its low pathogenicity. Many surveillance studies and activities conducted in several countries have shown the predominance of this virus subtype. We present the case of a 14-month-old female in Oman with an A(H9N2) virus infection. This is the first human case of A(H9N2) reported from Oman and the Gulf Cooperation Countries, and Oman is the second country outside of southern and eastern Asia to report a case (cases have also been detected in Egypt). The patient had bronchial asthma and presented with a high-grade temperature and symptoms of lower respiratory tract infection that necessitated admission to a high dependency unit in a tertiary care hospital. It is of urgency that a multisector One Health approach be established to combat the threat of avian influenza at the animal-human interface. In addition to enhancements of surveillance and control in poultry, there is a need to develop screening and preventive programs for high-risk occupations.

Molecular epidemiology of respiratory viruses in commercial chicken flocks in Pakistan from 2014 through to 2016

Background

Viral diseases are a matter of great concern for poultry farmers in Pakistan. Multiple common viral respiratory diseases (CVRDs) cause huge economic losses in the poultry industry. The prevalence of CVRDs in many countries, including Pakistan, is not clearly understood.

Results

Incidences of 5 chicken respiratory viruses: avian influenza virus (AIV), Newcastle disease virus (NDV/AAVV-1), infectious bronchitis virus (IBV), avian metapneumovirus (aMPV) and infectious laryngotracheitis virus (ILTV) were assessed on commercial Pakistani farms with respiratory problems from 2014 through to 2016. While AIV and AAVV-1 were frequently detected (16 to 17% of farms), IBV and aMPV were rarely detected (in 3 to 5% of farms) and ILTV was not detected. We characterized H9 AIV of the G1 lineage, genotype VII AAVV-1, GI-13 IBV, and type B aMPV strains with very little genetic variability in the 2-year study period. Co-infections with AIV and AAVV-1 were common and wild type AAVV-1 was detected despite the use of vaccines. Control measures to limit the virus burden in chicken flocks are discussed.

Conclusions

Our data shows that AIV (H9), AAVV-1, IBV and aMPV are prevalent in commercial poultry in Pakistan. Further studies are necessary to assess circulating strains, economic losses caused by infections and coinfections of these pathogens, and the costs and benefits of countermeasures. Furthermore, veterinarians and farmers should be informed of the pathogens circulating in the field and hence advised on the use of vaccines.

Amantadine resistance markers among low pathogenic avian influenza H9N2 viruses isolated from poultry in India, during 2009-2017

Antiviral susceptibility screening of avian influenza (AI) H9N2 viruses is crucial considering their role at the animal-human interface and potential to cause human infections. The Matrix 2 (M2) inhibitors (amantadine and rimantadine) have been used for prophylaxis and treatment of influenza A virus infections, however, resistance to these drugs has been widely reported. Information about amantadine susceptibility of H9N2 viruses from India is scanty. Matrix genes of 48H9N2 viruses isolated from India during 2009-2017 were sequenced and M2 trans-membrane region sequences were screened for mutations which are known to confer resistance to amantadine namely, L26F, V27A, A30 T/V, S31N and G34E. All the viruses isolated during the year 2009 were sensitive to amantadine. However, resistance started to appear since the year 2010 and all the viruses isolated from the year 2015 onwards showed presence of molecular markers conferring resistance to amantadine. Majority of the resistant viruses exhibited S31 N mutation. Four isolates showed presence of V27A + S31 N dual mutations. Comparison of the M2 sequences from other Asian countries showed different patterns of amantadine resistance wherein phylogenetic analysis of the M genes of the strains from Pakistan formed a separate cluster. In conclusion, the present study reports prevalence and gradual increase of amantadine resistance among AI H9N2 viruses in India, emphasizing the importance of the antiviral surveillance.

Continuing evolution of highly pathogenic H5N1 viruses in Bangladeshi live poultry markets

Since November 2008, we have conducted active avian influenza surveillance in Bangladesh. Clades 2.2.2, 2.3.4.2, and 2.3.2.1a of highly pathogenic avian influenza H5N1 viruses have all been identified in Bangladeshi live poultry markets (LPMs), although, since the end of 2014, H5N1 viruses have been exclusively from clade 2.3.2.1a. In June 2015, a new reassortant H5N1 virus (H5N1-R1) from clade 2.3.2.1a was identified, containing haemagglutinin, neuraminidase, and matrix genes of H5N1 viruses circulating in Bangladesh since 2011, plus five other genes of Eurasian-lineage low pathogenic avian influenza A (LPAI) viruses. Here we report the status of circulating avian influenza A viruses in Bangladeshi LPMs from March 2016 to January 2018. Until April 2017, H5N1 viruses exclusively belonged to H5N1-R1 clade 2.3.2.1a. However, in May 2017, we identified another reassortant H5N1 (H5N1-R2), also of clade 2.3.2.1a, wherein the PA gene segment of H5N1-R1 was replaced by that of another Eurasian-lineage LPAI virus related to A/duck/Bangladesh/30828/2016 (H3N8), detected in Bangladeshi LPM in September 2016. Currently, both reassortant H5N1-R1 and H5N1-R2 co-circulate in Bangladeshi LPMs. Furthermore, some LPAI viruses isolated from LPMs during 2016–2017 were closely related to those from ducks in free-range farms and wild birds in Tanguar haor, a wetland region of Bangladesh where ducks have frequent contact with migratory birds. These data support a hypothesis where Tanguar haor-like ecosystems provide a mechanism for movement of LPAI viruses to LPMs where reassortment with poultry viruses occurs adding to the diversity of viruses at this human-animal interface.

Development and evaluation of a new real-time RT-PCR assay for detecting the latest H9N2 influenza viruses capable of causing human infection

The H9N2 subtype of avian influenza A viruses (AIV) has spread among domestic poultry and wild birds worldwide. H9N2 AIV is sporadically transmitted to humans from avian species. A total of 42 laboratory‐confirmed cases of non‐fatal human infection with the Eurasian Y280 and G1 lineages have been reported in China, Hong Kong, Bangladesh and Egypt since 1997. H9N2 AIV infections in poultry have become endemic in Asia and the Middle East and are a major source of viral internal genes for other AIV subtypes, such that continuous monitoring of H9N2 AIV is recommended. In this study, a new, one‐step, real‐time RT‐PCR assay was developed to detect two major Eurasian H9 lineages of AIV capable of causing human infection. The sensitivity of this assay was determined using in vitro‐transcribed RNA, and the detection limit was approximately 3 copies/reaction. In this assay, no cross‐reactivity was observed against RNA from H1–15 subtypes of influenza A viruses, influenza B viruses and other viral respiratory pathogens. In addition, this assay could detect the H9 hemagglutinin (HA) gene from artificially reconstituted clinical samples spiked with H9N2 virus without any non‐specific reactions. Therefore, this assay is highly sensitive and specific for H9 HA detection. The assay is useful both for diagnostic purposes in cases of suspected human infection with influenza H9N2 viruses and for the surveillance of both avian and human influenza viruses.

Molecular characterization and receptor binding specificity of H9N2 avian influenza viruses based on poultry-related environmental surveillance in China between 2013 and 2016

H9N2 avian influenza viruses (AIVs) have become panzootic and caused sporadic human cases since 1998. Based on the poultry-related environmental surveillance data in mainland China from 2013 to 2016, a total of 68 representative environment isolates were selected and further investigated systematically. Phylogenetic analysis indicated that Y280-like H9N2 viruses have been predominant during 2013-2016 and acquired multiple specific amino acid substitutions that might favor viral transmission from avian to mammalians. Additionally, the viruses have undergone dramatic evolution and reassortment, resulting in an increased genetic diversity or acting as the gene contributors to new avian viruses. Receptor-binding tests indicated that most of the H9N2 isolates bound to human-type receptor, making them easily cross the species barrier and infect human efficiently. Our results suggested that the H9N2 AIVs prevalent in poultry may pose severe public health threat.

Review analysis and impact of co-circulating H5N1 and H9N2 avian influenza viruses in Bangladesh

Almost the full range of 16 haemagglutinin (HA) and nine neuraminidase subtypes of avian influenza viruses (AIVs) has been detected either in waterfowl, land-based poultry or in the environment in Bangladesh. AIV infections in Bangladesh affected a wide range of host species of terrestrial poultry. The highly pathogenic avian influenza (AI) H5N1 and low pathogenic AI H9N2 were found to co-circulate and be well entrenched in the poultry population, which has caused serious damage to the poultry industry since 2007. By reviewing the available scientific literature, the overall situation of AIVs in Bangladesh is discussed. All Bangladeshi (BD) H5N1 and H9N2 AIV sequences available at GenBank were downloaded along with other representative sequences to analyse the genetic diversity among the circulating AIVs in Bangladesh and to compare with the global situation. Three different H5N1 clades, 2.2.2, 2.3.2.1 and 2.3.4.2, have been detected in Bangladesh. Only 2.3.2.1a is still present. The BD LP H9N2 viruses mostly belonged to the H9 G1 lineage but segregated into many branches, and some of these shared internal genes with HP viruses of subtypes H7N3 and H5N1. However, these reassortment events might have taken place before introduction to Bangladesh. Currently, H9N2 viruses continue to evolve their HA cleavage, receptor binding and glycosylation sites. Multiple mutations in the HA gene associated with adaptation to mammalian hosts were also observed. Strict biosecurity at farms and gradual phasing out of live-bird markets could be the key measures to better control AIVs, whereas stamping out is not a practicable option in Bangladesh. Vaccination also could be an additional tool, which however, requires careful planning. Continuous monitoring of AIVs through systematic surveillance and genetic characterisation of the viruses remains a hallmark of AI control.

Evaluation of antiviral activity of Ocimum sanctum and Acacia arabica leaves extracts against H9N2 virus using embryonated chicken egg model

BACKGROUND

In the view of endemic avian influenza H9N2 infection in poultry, its zoonotic potential and emergence of antiviral resistance, two herbal plants, Ocimum sanctum and Acacia arabica, which are easily available throughout various geographical locations in India were taken up to study their antiviral activity against H9N2 virus. We evaluated antiviral efficacy of three different extracts each from leaves of O. sanctum (crude extract, terpenoid and polyphenol) and A. arabica (crude extract, flavonoid and polyphenol) against H9N2 virus using in ovo model.

METHODS

The antiviral efficacy of different leaves extracts was systematically studied in three experimental protocols viz. virucidal (dose-dependent), therapeutic (time-dependent) and prophylactic (dose-dependent) activity employing in ovo model. The maximum non-toxic concentration of each herbal extracts of O. sanctum and A. arabica in the specific pathogen free embryonated chicken eggs was estimated and their antiviral efficacy was determined in terms of reduction in viral titres, measured by Haemagglutination (HA) and real time quantitative reverse transcription polymerase chain reaction (RT-qPCR) assays.

RESULTS

All the extracts of O. sanctum (crude extract, terpenoid and polyphenol) and A. arabica (crude extract, flavonoid and polyphenol) showed significant virucidal activity, however, crude extract _ocimum and terpenoid _ocimum showed highly significant to significant (p < 0.001-0.01) decrease in virus genome copy numbers with lowest dose tested. Similarly, therapeutic effect was observed in all three extracts of O. sanctum in comparison to the virus control, nevertheless, crude extract _ocimum and terpenoid _ocimum maintained this effect for longer period of time (up to 72 h post-incubation). None of the leaves extracts of A. arabica had therapeutic effect at 24 and 48 h post-incubation, however, only the crude extract _acacia and polyphenol _acacia showed delayed therapeutic effect (72 h post-inoculation). Prophylactic potential was observed in polyphenol _acacia with highly significant antiviral activity compared to virus control (p < 0.001).

CONCLUSIONS

The crude extract and terpenoid isolated from the leaves of O. sanctum and polyphenol from A. arabica has shown promising antiviral properties against H9N2 virus. Future investigations are necessary to formulate combinations of these compounds for the broader antiviral activity against H9N2 viruses and evaluate them in chickens.

Full-length genome analysis of an avian influenza A virus (H9N2) from a human infection in Changsha City

Aim: Sequencing and phylogenetic analysis of avian influenza A (H9N2) virus strain, which was isolated from a 2-year-old child presenting influenza-like symptoms. Methods: Viral genome was acquired by RT-PCR, and phylogenetic trees were constructed using the neighbor-joining method. Results: A/Hunan/44557/2015 sequence shared identity with the RSSRGLF motif – first reported in low-pathogenic avian influenza in birds. Polymerase L336M and hemagglutinin Q226L mutation was found in the strain. Two newly mutation sites, T197D and D483N in hemagglutinin gene, were found. Phylogenetic tree analysis revealed that the eight gene segments of this virus contained three lineages. Conclusion: A/Hunan/44557/2015 may have acquired the ability to infect humans via genetic exchange with other H9N2 viruses, indicating that the H9N2 genome can generate pandemic isolates.

H9N2 avian influenza virus retained low pathogenicity after serial passage in chickens

The H9N2 strains of avian influenza viruses (AIVs) circulate worldwide in poultry and cause sporadic infection in humans. To better understand the evolution of these viruses while circulating in poultry, an H9N2 chicken isolate was passaged 19 times in chickens via aerosol inoculation. Whole-genome sequencing showed that the viruses from the initial stock and those after the 8th and 19th passages (P0, P8, and P19) all had the same monobasic cleavage site in the hemagglutinin (HA), typical for viruses of low pathogenicity. However, at position 226 of the HA protein the ratio of glutamine (which favors avian-type receptor binding) to leucine (which favors mammalian-type receptor binding) decreased from 54:46 in P0, to 87:13 in P8, and then 0:100 in P19. In chickens exposed to aerosols of P0, P8, or P19, replication of the viruses was similar and mainly limited to the respiratory tract. None of the infected chickens showed any clinical signs. Over the 19 passages the viruses maintained relatively stable infectivity but gradually lost lethality to chicken embryos. According to the hemagglutination inactivation assay, P8 was slightly and P19 significantly (P < 0.05) less thermostable than P0. Collectively, after 19 passages in chickens the H9N2 AIVs retained low pathogenicity with a positive selection of L226 in the HA. These findings suggest that H9N2 viruses might acquire mammalian specificity after asymptomatic circulation in avian species.

Influenza A(H9N2) Virus, Myanmar, 2014-2015

Routine surveillance of influenza A virus was conducted in Myanmar during 2014-2015. Influenza A(H9N2) virus was isolated in Shan State, upper Myanmar. Whole-genome sequencing showed that H9N2 virus from Myanmar was closely related to H9N2 virus of clade 4.2.5 from China.

Incidence of contamination of live bird markets in Bangladesh with influenza A virus and subtypes H5, H7 and H9

In the absence of robust active surveillance of avian influenza viruses (AIV) affecting poultry in South Asian countries, monitoring of live bird markets (LBMs) can be an alternative. In a longitudinal study of 32 LBM, five environments were sampled as follows: market floor, stall floor, slaughter area, poultry holding cage and water used for meat processing. Samples were taken monthly for 5 months, September 2013-January 2014. Incidence rates (IRs) of LBM contamination with AIV and its subtypes H5, H7 and H9 were assessed. In 10 of the LBM selected, biosecurity measures had been implemented through FAO interventions: the other 22 were non-intervened. Standard procedures were applied to detect AIV and three subtypes in pooled samples (1:5). An LBM was considered positive for AIV or a subtype if at least one of the pooled samples tested positive. The incidence rates of LBM contamination with AIV, H5, H7 and H9 were 0.194 (95% confidence interval (CI) 0.136-0.276), 0.031 (95% CI 0.013-0.075), 0 and 0.175 (95% CI 0.12-0.253) per LBM-month at risk, respectively. The log IR ratio between the FAO-intervened and non-intervened LBM for contamination with AIV was -0.329 (95% CI -1.052 to -0.394, p = .372), 0.598 (95% CI -1.593 to 2.789, p = .593) with subtype H5 and -0.500 (95% CI -1.249 to 0.248, p = .190) with subtype H9, indicating no significant difference. The results obtained suggest that both H5 and H9 were circulating in LBM in Bangladesh in the second half of 2013. The incidence of contamination with H9 was much higher than with H5.

Screening host proteins required for bacterial adherence after H9N2 virus infection

H9N2 subtype low pathogenic avian influenza virus (LPAIV) is distributed worldwide and causes great economic losses in the poultry industry, especially when complicated with other bacterial infections. Tissue damages caused by virus infection provide an opportunity for bacteria invasion, but this mechanism is not sufficient for low pathogenic strains. Moreover, although H9N2 virus infection was demonstrated to promote bacterial infection in several studies, its mechanism remained unclear. In this study, infection experiments in vivo and in vitro demonstrated that the adhesion of Escherichia coli (E. coli) to host cells significantly increased after H9N2 virus infection, and this increase was not caused by pathological damages. Subsequently, we constructed a late chicken embryo infection model and used proteomics techniques to analyze the expression of proteins associated with bacterial adhesion after H9N2 virus infection. A total of 279 significantly differential expressed proteins were detected through isobaric tags for relative and absolute quantitation (iTRAQ) coupled with nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS) analysis. The results of Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that differentially expressed proteins were enriched in host innate immunity; cell proliferation, differentiation, and apoptosis; and pathogenicity-related signaling pathways. Finally, we screened out several proteins, such as TGF-β1, integrins, cortactin, E-cadherin, vinculin, and fibromodulin, which were probably associated with bacterial adhesion. The study analyzed the mechanism of secondary bacterial infection induced by H9N2 virus infection from a novel perspective, which provided theoretical and data support for investigating the synergistic infection mechanism between the H9N2 virus and bacteria.

The Global Threat of Animal Influenza Viruses of Zoonotic Concern: Then and Now

Animal influenza viruses can reassort or mutate to infect and spread sustainably among people and cause a devastating worldwide pandemic. Since the first evidence of human infection with an animal influenza virus, in 1958, 16 different novel, zoonotic influenza A virus subtype groups in 29 countries, Taiwan, and Hong Kong have caused human infections, with differing severity and frequency. The frequency of novel influenza virus detection is increasing, and human infections with influenza A(H5N1) and A(H7N9) viruses are now annual seasonal occurrences in Asia. The study of the epidemiology and virology of animal influenza viruses is key to understanding pandemic risk and informing preparedness. This supplement brings together select recent articles that look at the risk of emergence and transmission of and approaches to prevent novel influenza virus infections.

Role of domestic ducks in the emergence of a new genotype of highly pathogenic H5N1 avian influenza A viruses in Bangladesh

Highly pathogenic avian influenza H5N1 viruses were first isolated in Bangladesh in February 2007. Subsequently, clades 2.2.2, 2.3.4.2 and 2.3.2.1a were identified in Bangladesh, and our previous surveillance data revealed that by the end of 2014, the circulating viruses exclusively comprised clade 2.3.2.1a. We recently determined the status of circulating avian influenza viruses in Bangladesh by conducting surveillance of live poultry markets and waterfowl in wetland areas from February 2015 through February 2016. Until April 2015, clade 2.3.2.1a persisted without any change in genotype. However, in June 2015, we identified a new genotype of H5N1 viruses, clade 2.3.2.1a, which quickly became predominant. These newly emerged H5N1 viruses contained the hemagglutinin, neuraminidase and matrix genes of circulating 2.3.2.1a Bangladeshi H5N1 viruses and five other genes of low pathogenic Eurasian-lineage avian influenza A viruses. Some of these internal genes were closely related to those of low pathogenic viruses isolated from ducks in free-range farms and wild birds in a wetland region of northeastern Bangladesh, where commercially raised domestic ducks have frequent contact with migratory birds. These findings indicate that migratory birds of the Central Asian flyway and domestic ducks in the free-range farms in Tanguar haor-like wetlands played an important role in the emergence of this novel genotype of highly pathogenic H5N1 viruses.

The Continuing Evolution of H5N1 and H9N2 Influenza Viruses in Bangladesh Between 2013 and 2014

In 2011, avian influenza surveillance at the Bangladesh live bird markets (LBMs) showed complete replacement of the highly pathogenic avian influenza (HPAI) H5N1 virus of clade 2.2.2 (Qinghai-like H5N1 lineage) by the HPAI H5N1 clade 2.3.2.1. This clade, which continues to circulate in Bangladesh and neighboring countries, is an intra-and interclade reassortant; its HA, polymerase basic 1 (PB1), polymerase (PA), and nonstructural (NS) genes come from subclade 2.3.2.1a; the polymerase basic 2 (PB2) comes from subclade 2.3.2.1c; and the NA, nucleocapsid protein (NP), and matrix (M) gene from clade 2.3.4.2. The H9N2 influenza viruses cocirculating in the Bangladesh LBMs are also reassortants, possessing five genes (NS, M, NP, PA, and PB1) from an HPAI H7N3 virus previously isolated in Pakistan. Despite frequent coinfection of chickens and ducks, reassortment between these H5N1 and H9N2 viruses has been rare. However, all such reassortants detected in 2011 through 2013 have carried seven genes from the local HPAI H5N1 lineage and the PB1 gene from the Bangladeshi H9N2 clade G1 Mideast, itself derived from HPAI H7N3 virus. Although the live birds we sampled in Bangladesh showed no clinical signs of morbidity, the emergence of this reassortant HPAI H5N1 lineage further complicates endemic circulation of H5N1 viruses in Bangladesh, posing a threat to both poultry and humans.

Insight into live bird markets of Bangladesh: an overview of the dynamics of transmission of H5N1 and H9N2 avian influenza viruses

Highly pathogenic avian influenza (HPAI) H5N1 and low pathogenic avian influenza (LPAI) H9N2 viruses have been recognized as threats to public health in Bangladesh since 2007. Although live bird markets (LBMs) have been implicated in the transmission, dissemination, and circulation of these viruses, an in-depth analysis of the dynamics of avian transmission of H5N1 and H9N2 viruses at the human-animal interface has been lacking. Here we present and evaluate epidemiological findings from active surveillance conducted among poultry in various production sectors in Bangladesh from 2008 to 2016. Overall, the prevalence of avian influenza viruses (AIVs) in collected samples was 24%. Our data show that AIVs are more prevalent in domestic birds within LBMs (30.4%) than in farms (9.6%). Quail, chickens and ducks showed a high prevalence of AIVs (>20%). The vast majority of AIVs detected (99.7%) have come from apparently healthy birds and poultry drinking water served as a reservoir of AIVs with a prevalence of 32.5% in collected samples. HPAI H5N1 was more frequently detected in ducks while H9N2 was more common in chickens and quail. LBMs, particularly wholesale markets, have become a potential reservoir for various types of AIVs, including HPAI H5N1 and LPAI H9N2. The persistence of AIVs in LBMs is of great concern to public health, and this study highlights the importance of regularly reviewing and implementing infection control procedures as a means of reducing the exposure of the general public to AIVs.Emerging Microbes & Infections (2017) 6, e12; doi:10.1038/emi.2016.142; published online 8 March 2017.

Genetic and antigenic evolution of H9N2 subtype avian influenza virus in domestic chickens in southwestern China, 2013-2016

H9N2 avian influenza virus (AIV) has caused significant losses in chicken flocks throughout china in recent years. There is a limited understanding of the genetic and antigenic characteristics of the H9N2 virus isolated in chickens in southwestern China. In this study a total of 12 field strains were isolated from tissue samples from diseased chickens between 2013 and 2016. Phylogenetic analysis of the Hemagglutinin (HA) and Neuraminidase (NA) nucleotide sequences from the 12 field isolates and other reference strains showed that most of the isolates in the past four years could be clustered into a major branch (HA-branch A and NA-branch I) in the Clade h9.4.2 lineages. These sequences are accompanied by nine and seven new amino acids mutations in the HA and NA proteins, respectively, when compared with those previous to 2013. In addition, four new isolates were grouped into a minor branch (HA-branch B) in the Clade h9.4.2 lineages and two potential N-glycosylation sites were observed due to amino acid mutations in the HA protein. Three antigenic groups (1-3), which had low antigenic relatedness with two commonly used vaccines in China, were identified among the 12 isolates by antigenMap analysis. Immunoprotection testing showed that those two vaccines could efficiently prevent the shedding of branch A viruses but not branch B viruses. In conclusion, these results indicate the genotype of branch B may become epidemic in the next few years and that a new vaccine should be developed for the prevention of H9N2 AIV.

Highly Pathogenic Reassortant Avian Influenza A(H5N1) Virus Clade 2.3.2.1a in Poultry, Bhutan

Highly pathogenic avian influenza A(H5N1), clade 2.3.2.1a, with an H9-like polymerase basic protein 1 gene, isolated in Bhutan in 2012, replicated faster in vitro than its H5N1 parental genotype and was transmitted more efficiently in a chicken model. These properties likely help limit/eradicate outbreaks, combined with strict control measures.

The avian influenza H9N2 at avian-human interface: A possible risk for the future pandemics

The avian influenza subtype H9N2 is considered a low pathogenic virus which is endemic in domestic poultry of a majority of Asian countries. Many reports of seropositivity in occupationally poultry-exposed workers and a number of confirmed human infections with an H9N2 subtype of avian influenza have been documented up to now. Recently, the human infections with both H7N9 and H10N8 viruses highlighted that H9N2 has a great potential for taking a part in the emergence of new human-infecting viruses. This review aimed at discussing the great potential of H9N2 virus which is circulating at avian-human interface, for cross-species transmission, contribution in the production of new reassortants and emergence of new pandemic subtypes. An intensified surveillance is needed for controlling the future risks which would be created by H9N2 circulation at avian-human interfaces.

Replication Capacity of Avian Influenza A(H9N2) Virus in Pet Birds and Mammals, Bangladesh

Avian influenza A(H9N2) is an agricultural and public health threat. We characterized an H9N2 virus from a pet market in Bangladesh and demonstrated replication in samples from pet birds, swine tissues, human airway and ocular cells, and ferrets. Results implicated pet birds in the potential dissemination and zoonotic transmission of this virus.

H9N2 low pathogenic avian influenza in Pakistan (2012-2015)

Significant economic losses from deaths and decreased egg production have resulted from H9N2 low pathogenic avian influenza virus (LPAIV) infections in poultry across North Africa, the Middle East and Asia. The H9N2 LPAIVs have been endemic in Pakistani poultry since 1996, but no new viruses have been reported since 2010. Because novel genotypes of Pakistani H9N2 contain mammalian host-specific markers, recent surveillance is essential to better understand any continuing public health risk. Here the authors report on four new H9N2 LPAIVs, three from 2015 and one from 2012. All of the viruses tested in this study belonged to Middle East B genetic group of G1 lineage and had PAKSSR/G motif at the haemagglutinin cleavage site. The mammalian host-specific markers at position 226 in the haemagglutinin receptor-binding site and internal genes suggest that Pakistan H9N2 viruses are still potentially infectious for mammals. Continued active surveillance in poultry and mammals is needed to monitor the spread and understand the potential for zoonotic infection by these H9N2 LPAIVs.

Raising Backyard Poultry in Rural Bangladesh: Financial and Nutritional Benefits, but Persistent Risky Practices

Poultry is commonly raised by households in rural Bangladesh. In 2007, the Government of Bangladesh began a mass media campaign to disseminate 10 recommended precautions to prevent transmission of H5N1 from poultry to humans. This longitudinal study explored the contribution of backyard poultry on household economy and nutrition and compared poultry-raising practices to government recommendations. From 2009 to 2012, we enrolled a nationally representative sample of 2489 primary backyard poultry raisers from 115 rural villages selected by probability proportional to population size. Researchers interviewed the raisers to collect data on poultry-raising practices. They followed the raisers for 2-12 months to collect data on household income and nutrition from poultry. Income from backyard poultry flocks accounted for 2.8% of monthly household income. Return on annual investment (ROI) per flock was 480%. Yearly, median family consumption of eggs was one-fifth of the total produced eggs and three poultry from their own flock. Respondents' reported practices conflicted with government recommendations. Sixty per cent of raisers had never heard of avian influenza or 'bird flu'. Among the respondents, 85% handled sick poultry or poultry that died due to illness, and 49% slaughtered or defeathered sick poultry. In 37% of households, children touched poultry. Fifty-eight per cent never washed their hands with soap after handling poultry, while <1% covered their nose and mouth with a cloth when handling poultry. Only 3% reported poultry illness and deaths to local authorities. These reported practices did not improve during the study period. Raising backyard poultry in rural Bangladesh provides important income and nutrition with an excellent ROI. Government recommendations to reduce the risk of avian influenza transmission did not impact the behaviour of poultry producers. Further research should prioritize developing interventions that simultaneously reduce the risk of avian influenza transmission and increase productivity of backyard poultry.

The replication of Bangladeshi H9N2 avian influenza viruses carrying genes from H7N3 in mammals

H9N2 avian influenza viruses are continuously monitored by the World Health Organization because they are endemic; they continually reassort with H5N1, H7N9 and H10N8 viruses; and they periodically cause human infections. We characterized H9N2 influenza viruses carrying internal genes from highly pathogenic H7N3 viruses, which were isolated from chickens or quail from live-bird markets in Bangladesh between 2010 and 2013. All of the H9N2 viruses used in this study carried mammalian host-specific mutations. We studied their replication kinetics in normal human bronchoepithelial cells and swine tracheal and lung explants, which exhibit many features of the mammalian airway epithelium and serve as a mammalian host model. All H9N2 viruses replicated to moderate-to-high titers in the normal human bronchoepithelial cells and swine lung explants, but replication was limited in the swine tracheal explants. In Balb/c mice, the H9N2 viruses were nonlethal, replicated to moderately high titers and the infection was confined to the lungs. In the ferret model of human influenza infection and transmission, H9N2 viruses possessing the Q226L substitution in hemagglutinin replicated well without clinical signs and spread via direct contact but not by aerosol. None of the H9N2 viruses tested were resistant to the neuraminidase inhibitors. Our study shows that the Bangladeshi H9N2 viruses have the potential to infect humans and highlights the importance of monitoring and characterizing this influenza subtype to better understand the potential risk these viruses pose to humans.

Recombinant Newcastle disease virus expressing H9 HA protects chickens against heterologous avian influenza H9N2 virus challenge

In order to produce an efficient poultry H9 avian influenza vaccine that provides cross-protection against multiple H9 lineages, two Newcastle disease virus (NDV) LaSota vaccine strain recombinant viruses were generated using reverse genetics. The recombinant NDV-H9Con virus expresses a consensus-H9 hemagglutinin (HA) that is designed based on available H9N2 sequences from Chinese and Middle Eastern isolates. The recombinant NDV-H9Chi virus expresses a chimeric-H9 HA in which the H9 ectodomain of A/Guinea Fowl/Hong Kong/WF10/99 was fused with the cytoplasmic and transmembrane domain of the fusion protein (F) of NDV. Both recombinant viruses expressed the inserted HA stably and grew to high titers. An efficacy study in chickens showed that both recombinant viruses were able to provide protection against challenge with a heterologous H9N2 virus. In contrast to the NDV-H9Chi virus, the NDV-H9Con virus induced a higher hemagglutination inhibition titer against both NDV and H9 viruses in immunized birds, and efficiently inhibited virus shedding through the respiratory route. Moreover, sera collected from birds immunized with either NDV-H9Con or NDV-H9Chi were able to cross-neutralize two different lineages of H9N2 viruses, indicating that NDV-H9Con and NDV-H9Chi are promising vaccine candidates that could provide cross-protection among different H9N2 lineage viruses.

Serological evidence of H9N2 avian influenza virus exposure among poultry workers from Fars province of Iran

Background

Since the 1990s, influenza A viruses of the H9N2 subtype have been causing infections in the poultry population around the globe. This influenza subtype is widely circulating in poultry and human cases of AI H9N2 have been sporadically reported in countries where this virus is endemic in domestic birds. The wide circulation of H9N2 viruses throughout Europe and Asia along with their ability to cause direct infection in mammals and humans, raises public health concerns. H9N2 AI was reported for the first time in Iran in 1998 and at present it is endemic in poultry. This study was carried out to evaluate the exposure to H9N2 AI viruses among poultry workers from the Fars province.

Methods

100 poultry workers and 100 healthy individuals with no professional exposure to poultry took part in this study. Serum samples were tested for antibodies against two distinct H9N2 avian influenza viruses, which showed different phylogenetic clustering and important molecular differences, such as at the amino acid (aa) position 226 (Q/L) (H3 numbering), using haemagglutination inhibition (HI) and microneutralization (MN) assays.

Results

Results showed that 17 % of the poultry workers were positive for the A/chicken/Iran/10VIR/854-5/2008 virus in MN test and 12 % in HI test using the titer ≥40 as positive cut-off value. Only 2 % of the poultry workers were positive for the A/chicken/Iran/12VIR/9630/1998 virus. Seroprevalence of non exposed individuals for both H9N2 strains was below 3 % by both tests. Statistical analyses models showed that exposure to poultry significantly increases the risk of infection with H9N2 virus.

Conclusions

The results have demonstrated that exposure to avian H9N2 viruses had occurred among poultry workers in the Fars province of Iran. Continuous surveillance programmes should be implemented to monitor the presence of avian influenza infections in humans and to evaluate their potential threat to poultry workers and public health.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-016-0472-z) contains supplementary material, which is available to authorized users.

Influenza A virus transmission via respiratory aerosols or droplets as it relates to pandemic potential

Many respiratory viruses of humans originate from animals. For instance, there are now eight paramyxoviruses, four coronaviruses and four orthomxoviruses that cause recurrent epidemics in humans but were once confined to other hosts. In the last decade, several members of the same virus families have jumped the species barrier from animals to humans. Fortunately, these viruses have not become established in humans, because they lacked the ability of sustained transmission between humans. However, these outbreaks highlighted the lack of understanding of what makes a virus transmissible. In part triggered by the relatively high frequency of occurrence of influenza A virus zoonoses and pandemics, the influenza research community has started to investigate the viral genetic and biological traits that drive virus transmission via aerosols or respiratory droplets between mammals. Here we summarize recent discoveries on the genetic and phenotypic traits required for airborne transmission of zoonotic influenza viruses of subtypes H5, H7 and H9 and pandemic viruses of subtypes H1, H2 and H3. Increased understanding of the determinants and mechanisms of respiratory virus transmission is not only key from a basic scientific perspective, but may also aid in assessing the risks posed by zoonotic viruses to human health, and preparedness for such risks.

Reassortant Avian Influenza A(H9N2) viruses in chickens in retail poultry shops, Pakistan, 2009-2010

Phylogenetic analysis of influenza viruses collected during December 2009–February 2010 from chickens in live poultry retail shops in Lahore, Pakistan, showed influenza A(H9N2) lineage polymerase and nonstructural genes generate through inter- and intrasubtypic reassortments. Many amino acid signatures observed were characteristic of human isolates; hence, their circulation could enhance inter- or intrasubtypic reassortment.

Lactobacillus plantarum vaccine vector expressing hemagglutinin provides protection against H9N2 challenge infection

Hemagglutinin (HA) has been demonstrated as an effective candidate vaccine antigen against AIVs. Dendritic cell-targeting peptide (DCpep) can enhance the robustness of immune responses. The purpose of this study was to evaluate whether DCpep could enhance the immune response against H9N2 AIV when utilizing Lactobacillus plantarum NC8 (NC8) to present HA-DCpep in mouse and chicken models. To accomplish this, a mucosal vaccine of a recombinant NC8 strain expressing HA and DCpep that was constructed in a previous study was employed. Orally administered NC8-pSIP409-HA-DCpep elicited high serum titers of hemagglutination-inhibition (HI) antibodies in mice and also induced robust T cell immune responses in both mouse and chicken models. Orally administered NC8-pSIP409-HA-DCpep elicited high serum titers of hemagglutination-inhibition (HI) antibodies in mice and also induced robust T cell immune responses in both mouse and chicken models. These results revealed that recombinant L. plantarum NC8-pSIP409-HA-DCpep is an effective vaccine candidate against H9N2 AIVs.

Molecular characterization of H9N2 avian influenza viruses isolated from vaccinated broiler chickens in northeast Iran

Avian influenza is a highly contagious respiratory disease of poultry caused by influenza A viruses, family Orthomyxoviridae. H9N2 avian influenza outbreaks are a major problem of the poultry industry in Iran. To determine the genetic differences between field viruses and the vaccine strain, the genomes of four strains isolated in 2011 from vaccinated broiler flocks with a history of respiratory illness were sequenced. Genetic and serological comparisons were made. Sequence analysis of the hemagglutinin (HA) and neuraminidase (NA) genes indicated that the isolated strains shared nucleotide homologies of 91.6-93.9 and 90.2-91.7% with the vaccine strain, respectively. Phylogenetic analyses of HA and NA genes showed that all strains isolated in this study fell into the same group and belonged to the influenza A virus (A)/quail/Hong Kong/G1/97 H9N2 sublineage. Several amino acids have changed at the antigenic sites in HA in the field viruses. Extra potential glycosylation sites were observed in the HA and NA proteins expressed by the current isolates relative to those in the vaccine strain. The deduced amino acid sequence at the cleavage site of HA in recent isolates is the KSSR/GLF motif, whereas it is RSSR/GLF in the vaccine strain. A serological analysis revealed that the currently circulating strains are antigenically distinct from the vaccine strain. These results suggest that the commercial vaccine is insufficiently genetically and antigenically similar to the viruses currently circulating in the region. These findings confirm that it is important to monitor the genetic and antigenic variations in H9N2 influenza viruses when selecting a vaccine strain.