Low Pathogenic Avian Influenza H5 Research Articles

Annual Report on surveillance for avian influenza in poultry and wild birds in Member States of the European Union in 2020.

In 2020, Council Directive 2005/94/EC required EU Member States (MSs) to carry out surveillance for avian influenza (AI) in poultry and wild birds and notify the results to the responsible authority. Based on this, MSs, Iceland, Norway, Switzerland and the United Kingdom implemented ongoing surveillance programmes to monitor incursions of AI viruses in poultry and wild birds. EFSA received a mandate from the European Commission to collate, validate, analyse and summarise the data resulting from the avian influenza surveillance programmes in an annual report. This is the second such report produced using data directly submitted to EFSA by MSs. This report summarises the results of the surveillance activities carried out in poultry and wild birds in 2020. Overall, 24,768 poultry establishments (PEs) were sampled, of which 46 were seropositive for H5 virus strains and seven for H7 strains. Seropositive PEs were found in nine MSs (Belgium, Denmark, Finland, France, Italy, the Netherlands, Poland, Spain and Sweden) and the United Kingdom. As per previous years, the highest percentages of seropositive PEs were found in establishments raising waterfowl game birds and breeding geese. Out of the 53 PEs with positive serological tests for H5/H7, seven tested positive in polymerase chain reaction (PCR) or virology for H5/H7 virus strains: six for Low Pathogenic Avian Influenza (LPAI) and one for Highly Pathogenic Avian Influenza (HPAI). In addition, 13 countries also reported PCR results from 748 PEs which did not correspond to the follow‐up testing of a positive serology event (e.g. in some PEs, PCR tests were used for screening). Twenty‐five of these PEs were found positive for AI viral RNA. These positive PEs were located in Bulgaria, Estonia, Germany, Romania and Slovakia. A total of 18,968 wild birds were sampled, with 878 birds testing positive to HPAI virus. Fourteen countries reported HPAI‐positive wild birds, with all HPAI strains identified as H5. Most positive birds were infected with H5N8, with a smaller number of N1, N3, N5 and unidentified NA subtypes. In addition, there were 317 birds testing positive for LPAI H5 or H7 virus and 429 birds testing positive for non‐H5/H7 AI virus, reported by 31 countries. The surveillance findings for poultry and wild birds for 2020 are discussed in relation to the current knowledge of the epidemiology of AI in Europe, in particular the H5N8 epidemic which has been identified late 2020.

Quantitative risk assessment of the introduction of low pathogenic avian influenza H5 and H7 strains into Poland via legal import of live poultry

Low pathogenic avian influenza (LPAI) caused by H5 and H7 viruses is considered a threatening disease for poultry production due to the possibility of prolonged undetected virus circulation in a poultry flock and its potential to mutate to highly pathogenic avian influenza (HPAI). The occurrence of HPAI may have devastating impact on the poultry industry and has serious economic consequences. The possibility of LPAI virus (LPAIV) being introduced into Poland via import of live poultry from EU countries was considered. The main aim of the study was to quantitatively assess the probability of LPAIV H5 and H7 introduction into Poland (PLPAI) via this pathway, to evaluate the relative contribution of exporting countries and species of poultry to this probability and to present the spatial distribution of the introduction probability in Poland. To this end, a stochastic multilevel binomial risk model, taking into account uncertainty and variability of input parameter values, was developed. The results of this model indicate that the mean annual probability of LPAIV H5 or H7 introduction into Poland is 0.088 [95 % uncertainty interval: 0.0575, 0.128], which corresponds to, on average, one outbreak every 11 years. The countries contributing most to this probability are Germany, Czech Republic and Denmark. Importations of ducks, chickens and turkeys contribute most to PLPAI, whereas importations of geese and guinea fowl represent a minor risk. The probability of LPAIV introduction is not equally distributed across Poland with the majority of counties having a high probability of LPAIV introduction being located in the Western part of the country.The results of this study can be used to support decision makers on targeted prevention or risk-based surveillance strategies for LPAI.

Serologic Evidence of Exposure to Highly Pathogenic Avian Influenza H5 Viruses in Migratory Shorebirds, Australia.

Highly pathogenic avian influenza (HPAI) H5Nx viruses of the goose/Guangdong/96 lineage continue to cause outbreaks in poultry and wild birds globally. Shorebirds, known reservoirs of avian influenza viruses, migrate from Siberia to Australia along the East-Asian-Australasian Flyway. We examined whether migrating shorebirds spending nonbreeding seasons in Australia were exposed to HPAI H5 viruses. We compared those findings with those for a resident duck species. We screened >1,500 blood samples for nucleoprotein antibodies and tested positive samples for specific antibodies against 7 HPAI H5 virus antigens and 2 low pathogenicity avian influenza H5 virus antigens. We demonstrated the presence of hemagglutinin inhibitory antibodies against HPAI H5 virus clade 2.3.4.4 in the red-necked stint (Calidris ruficolis). We did not find hemagglutinin inhibitory antibodies in resident Pacific black ducks (Anas superciliosa). Our study highlights the potential role of long-distance migratory shorebirds in intercontinental spread of HPAI H5 viruses.

Highly Pathogenic and Low Pathogenic Avian Influenza H5 Subtype Viruses in Wild Birds in Ukraine.

There have been three waves of highly pathogenic avian influenza (HPAI) outbreaks in commercial, backyard poultry, and wild birds in Ukraine. The first (2005-2006) and second (2008) waves were caused by H5N1 HPAI virus, with 45 outbreaks among commercial poultry (chickens) and backyard fowl (chickens, ducks, and geese) in four regions of Ukraine (AR Crimea, Kherson, Odesa, and Sumy Oblast). H5N1 HPAI viruses were isolated from dead wild birds: cormorants (Phalacrocorax carbo) and great crested grebes (Podiceps cristatus) in 2006 and 2008. The third HPAI wave consisted of nine outbreaks of H5N8 HPAI in wild and domestic birds, beginning in November 2016 in the central and south regions (Kherson, Odesa, Chernivtsi, Ternopil, and Mykolaiv Oblast). H5N8 HPAI virus was detected in dead mute swans (Cygnus olor), peacocks (Pavo cristatus) (in zoo), ruddy shelducks (Tadorna ferruginea), white-fronted geese (Anser albifrons), and from environmental samples in 2016 and 2017. Wide wild bird surveillance for avian influenza (AI) virus was conducted from 2006 to 2016 in Ukraine regions suspected of being intercontinental (north-south and east-west) flyways. A total of 21 511 samples were collected from 105 species of wild birds representing 27 families and 11 orders. Ninety-five avian influenza (AI) viruses were isolated (including one H5N2 LPAI virus in 2010) from wild birds with a total of 26 antigenic hemagglutinin (HA) and neuraminidase (NA) combinations. Fifteen of 16 known avian HA subtypes were isolated. Two H5N8 HPAI viruses (2016-2017) and two H5N2 LPAI viruses (2016) were isolated from wild birds and environmental samples (fresh bird feces) during surveillance before the outbreak in poultry in 2016-2017. The Ukrainian H5N1, H5N8 HPAI, and H5N2 LPAI viruses belong to different H5 phylogenetic groups. Our results demonstrate the great diversity of AI viruses in wild birds in Ukraine, as well as the importance of this region for studying the ecology of avian influenza.

Serological evidence of influenza virus infection in captive wild felids, Thailand

Influenza virus is known to affect wild felids. To explore the prevalence of influenza viruses in these animal species, 196 archival sera from 5 felid species including Panthera tigris (N=147), Prionailurus viverrinus (N=35), Panthera leo (N=5), Pardofelis temminckii (N=8) and Neofelis nebulosa (N=1) collected between 2011 and 2015 in 10 provinces of Thailand were determined for the presence of antibody to avian and human influenza viruses. Blocking enzyme-linked immunosorbent (ELISA) assay and hemagglutination inhibition (HI) assay were employed as the screening tests, which the serum samples with HI antibody titers ≥20 were further confirmed by cytopathic effect/hemagglutination based-microneutralization (CPE/HA-based microNT) test. Based on HI and microNT assays, the seropositive rates of low pathogenic avian influenza (LPAI) H5 virus, highly pathogenic avian influenza (HPAI) H5 virus and human H1 virus were 1.53% (3/196), 2.04% (4/196) and 6.63% (13/196), respectively. In addition, we also found antibody against both LPAI H5 virus and HPAI H5 virus in 2 out of 196 tested sera (1.02%). Evidences of influenza virus infection were found in captive P. tigris in Kanchanaburi, Nakhon Sawan and Ratchaburi provinces of Thailand. The findings of our study highlights the need of a continuous active surveillance program of influenza viruses in wild felid species.

Highly Pathogenic and Low Pathogenic Avian Influenza H5 Subtype Viruses in Wild Birds in Ukraine.

There have been three waves of highly pathogenic avian influenza (HPAI) outbreaks in commercial, backyard poultry, and wild birds in Ukraine. The first (2005-2006) and second (2008) waves were caused by H5N1 HPAI virus, with 45 outbreaks among commercial poultry (chickens) and backyard fowl (chickens, ducks, and geese) in four regions of Ukraine (AR Crimea, Kherson, Odesa, and Sumy Oblast). H5N1 HPAI viruses were isolated from dead wild birds: cormorants (Phalacrocorax carbo) and great crested grebes (Podiceps cristatus) in 2006 and 2008. The third HPAI wave consisted of nine outbreaks of H5N8 HPAI in wild and domestic birds, beginning in November 2016 in the central and south regions (Kherson, Odesa, Chernivtsi, Ternopil, and Mykolaiv Oblast). H5N8 HPAI virus was detected in dead mute swans (Cygnus olor), peacocks (Pavo cristatus) (in zoo), ruddy shelducks (Tadorna ferruginea), white-fronted geese (Anser albifrons), and from environmental samples in 2016 and 2017. Wide wild bird surveillance for avian influenza (AI) virus was conducted from 2006 to 2016 in Ukraine regions suspected of being intercontinental (north-south and east-west) flyways. A total of 21 511 samples were collected from 105 species of wild birds representing 27 families and 11 orders. Ninety-five avian influenza (AI) viruses were isolated (including one H5N2 LPAI virus in 2010) from wild birds with a total of 26 antigenic hemagglutinin (HA) and neuraminidase (NA) combinations. Fifteen of 16 known avian HA subtypes were isolated. Two H5N8 HPAI viruses (2016-2017) and two H5N2 LPAI viruses (2016) were isolated from wild birds and environmental samples (fresh bird feces) during surveillance before the outbreak in poultry in 2016-2017. The Ukrainian H5N1, H5N8 HPAI, and H5N2 LPAI viruses belong to different H5 phylogenetic groups. Our results demonstrate the great diversity of AI viruses in wild birds in Ukraine, as well as the importance of this region for studying the ecology of avian influenza.

Novel Avian Influenza A(H5N8) Viruses in Migratory Birds, China, 2013-2014.

Novel Avian Influenza A(H5N8) Viruses in Migratory Birds, China, 2013-2014.

Avian influenza in Australia: a summary of 5 years of wild bird surveillance.

Avian influenza viruses (AIVs) are found worldwide in numerous bird species, causing significant disease in gallinaceous poultry and occasionally other species. Surveillance of wild bird reservoirs provides an opportunity to add to the understanding of the epidemiology of AIVs. This study examined key findings from the National Avian Influenza Wild Bird Surveillance Program over a 5-year period (July 2007-June 2012), the main source of information on AIVs circulating in Australia. The overall proportion of birds that tested positive for influenza A via PCR was 1.9 ± 0.1%, with evidence of widespread exposure of Australian wild birds to most low pathogenic avian influenza (LPAI) subtypes (H1-13, H16). LPAI H5 subtypes were found to be dominant and widespread during this 5-year period. Given Australia's isolation, both geographically and ecologically, it is important for Australia not to assume that the epidemiology of AIV from other geographic regions applies here. Despite all previous highly pathogenic avian influenza outbreaks in Australian poultry being attributed to H7 subtypes, widespread detection of H5 subtypes in wild birds may represent an ongoing risk to the Australian poultry industry.

Characterization of low-pathogenicity H5 and H7 Korean avian influenza viruses in chickens

To date, all isolated highly pathogenic avian influenza (HPAI) viruses that cause systemic infection with a high mortality rate in poultry species have been known to belong to either the H5 or H7 subtypes. The HPAI viruses may originate because of the insertion of multiple basic amino acids at the cleavage site of the hemagglutinin protein after the low-pathogenic H5 and H7 viruses have been introduced into poultry. In the present study, we investigated the phylogenetic characteristics of the H5 (n = 4) and H7 (n = 3) low-pathogenic avian influenza (LPAI) viruses isolated from wild birds in Korea by using nucleotide sequences of all 8 gene segments of the viral genome. Further, we evaluated the infectivity, transmissibility, and pathogenic potential of these viruses in chickens. Phylogenetic analysis showed that all viruses used in the study clustered in the Eurasian lineage and were similar to the viruses isolated in Asian countries that share the East Asian–Australasian migratory bird flyway. Our H5N2 isolates could not be replicated and transmitted in chickens, but the H7N8 isolates could efficiently be replicated and transmitted to contact-exposure chickens. In addition, because our H7N8 isolates caused watery diarrhea in chickens, these viruses cannot only serve as progenitors of novel HPAI strains but also potentially cause clinical disease in poultry. Although there have been no reports of LPAI mutation to HPAI in these regions, the wild bird surveillance effort should focus on monitoring the introduction and transmission of the HPAI H5N1 and LPAI H5 and H7 viruses.

Avian Influenza A Virus Monitoring in Wild Birds in Bavaria: Occurrence and Heterogeneity of H5 and N1 Encoding Genes

To define avian influenza virus prevalence in wild birds in Bavaria, 12,930 tracheal, cloacal swabs or tissue samples from various waterfowl species were screened between January 2006 and December 2007. In 291 (2.3%) birds, genomes of influenza A viruses were detected by reverse transcription real-time PCR (rRT-PCR) targeting the matrix protein genes. Furthermore, solitary H5 hemagglutinin or N1 neuraminidase encoding genes were identified in 35 (0.3%) apparently healthy birds; whereas highly pathogenic (HPAI) H5N1 virus genomes were only diagnosed in dead wild birds (n = 93; 0.7%) found across this federal state region. In this study, multiple import events for H5N1 viruses were confirmed during 2006 and 2007. In addition, our findings argue against an existing HPAI H5N1 reservoir in aquatic birds in Bavaria. By contrast, phylogenetic analyses of the H5 or N1 sequences of low pathogenic avian influenza (LPAI) viruses revealed a marked diversity and multiple genetic lineages. This diversity of LPAI H5 and N1 subtype components indicates the existence of LPAI HA and NA gene pools which differ from the Bavarian HPAI H5N1. Moreover, the hemagglutinin amino acid differences between LPAI H5 viruses of a western European genotypic lineage observed in wild birds suggest a continuous evolution of LPAI viruses in Bavaria.

Characterization of H5N2 influenza viruses isolated in South Korea and their influence on the emergence of a novel H9N2 influenza virus

We characterized low pathogenic avian influenza (LPAI) H5N2 and H9N2 viruses isolated in South Korea from 2008 to 2009. Genetic analysis of the H5N2 viruses isolated from wild birds and domestic ducks demonstrated that they were related to the recently isolated southern Chinese LPAI H5 viruses and various influenza viruses circulating in Eurasia. Three H9N2 viruses obtained at live bird markets and duck farms were reassortant viruses generated from the H5N2 viruses of domestic ducks and the H9N2 virus endemic in Korean chickens. The H5N2 viruses did not replicate well in experimentally infected chickens and mice, but novel H9N2 viruses, without pre-adaptation, were recovered at high titres in chickens. Our results show that reassortment between H5N2 and H9N2 viruses must have occurred in domestic ducks and may have contributed to the diversity expansion of the gene pool, which has potential to alter the pathogenicity and host range of the influenza virus.

Surveillance for Avian Influenza in Wild Birds in the European Union in 2007

Surveillance of wild birds for avian influenza viruses has been compulsory in the European Union (EU) since 2005, primarily as a means of detecting H5N1 highly pathogenic avian influenza (HPAI) virus and of monitoring the circulation of low pathogenicity avian influenza (LPAI) virus H5 and H7 strains. In 2007, 79,392 wild birds were tested throughout the EU. H5N1 HPAI was detected in 329 birds from four Member States (MS); affected birds were almost entirely of the orders Podicipediformes (grebes) and Anseriformes (waterfowl) during the summer months. LPAI was detected in 1485 wild birds among 21 MS. A total of 1250 birds were positive for influenza A but were not discriminated any further; LPAI H5 was detected in 105 birds, exclusively of the order Anseriformes. LPAI H7 was detected in seven birds. LPAI of other subtypes was found in 123 birds. Epidemiologic evidence and phylogenetic analysis of H5N1 viruses indicate that H5N1 did not appear to persist in the EU from 2006 but was reintroduced, probably from the Middle East.

Efficacy of a Replikin Peptide Vaccine against Low Pathogenicity Avian Influenza H5 Virus

Efficacy of a Replikin Peptide Vaccine against Low Pathogenicity Avian Influenza H5 Virus

Australian surveillance for avian influenza viruses in wild birds between July 2005 and June 2007

To identify and gain an understanding of the influenza viruses circulating in wild birds in Australia. A total of 16,303 swabs and 3782 blood samples were collected and analysed for avian influenza (AI) viruses from 16,420 wild birds in Australia between July 2005 and June 2007. Anseriformes and Charadriiformes were primarily targeted. Cloacal, oropharyngeal and faecal (environmental) swabs were tested using polymerase chain reaction (PCR) for the AI type A matrix gene. Positive samples underwent virus culture and subtyping. Serum samples were analysed using a blocking enzyme-linked immunosorbent assay for influenza A virus nucleoprotein. No highly pathogenic AI viruses were identified. However, 164 PCR tests were positive for the AI type A matrix gene, 46 of which were identified to subtype. A total of five viruses were isolated, three of which had a corresponding positive PCR and subtype identification (H3N8, H4N6, H7N6). Low pathogenic AI H5 and/or H7 was present in wild birds in New South Wales, Tasmania, Victoria and Western Australia. Antibodies to influenza A were also detected in 15.0% of the birds sampled. Although low pathogenic AI virus subtypes are currently circulating in Australia, their prevalence is low (1.0% positive PCR). Surveillance activities for AI in wild birds should be continued to provide further epidemiological information about circulating viruses and to identify any changes in subtype prevalence.

Characterization of Low-Pathogenic H5 Subtype Influenza Viruses from Eurasia: Implications for the Origin of Highly Pathogenic H5N1 Viruses

Highly pathogenic avian influenza (HPAI) H5N1 viruses are now endemic in many Asian countries, resulting in repeated outbreaks in poultry and increased cases of human infection. The immediate precursor of these HPAI viruses is believed to be A/goose/Guangdong/1/96 (Gs/GD)-like H5N1 HPAI viruses first detected in Guangdong, China, in 1996. From 2000 onwards, many novel reassortant H5N1 influenza viruses or genotypes have emerged in southern China. However, precursors of the Gs/GD-like viruses and their subsequent reassortants have not been fully determined. Here we characterize low-pathogenic avian influenza (LPAI) H5 subtype viruses isolated from poultry and migratory birds in southern China and Europe from the 1970s to the 2000s. Phylogenetic analyses revealed that Gs/GD-like virus was likely derived from an LPAI H5 virus in migratory birds. However, its variants arose from multiple reassortments between Gs/GD-like virus and viruses from migratory birds or with those Eurasian viruses isolated in the 1970s. It is of note that unlike HPAI H5N1 viruses, those recent LPAI H5 viruses have not become established in aquatic or terrestrial poultry. Phylogenetic analyses revealed the dynamic nature of the influenza virus gene pool in Eurasia with repeated transmissions between the eastern and western extremities of the continent. The data also show reassortment between influenza viruses from domestic and migratory birds in this region that has contributed to the expanded diversity of the influenza virus gene pool among poultry in Eurasia.