Avian Influenza Virus and Avian Paramyxoviruses in Wild Waterfowl of the Western Coast of the Caspian Sea (2017-2020).

The flyways of many different wild waterfowl pass through the Caspian Sea region. The western coast of the middle Caspian Sea is an area with many wetlands, where wintering grounds with large concentrations of birds are located. It is known that wild waterfowl are a natural reservoir of the influenza A virus. In the mid-2000s, in the north of this region, the mass deaths of swans, gulls, and pelicans from high pathogenicity avian influenza virus (HPAIV) were noted. At present, there is still little known about the presence of avian influenza virus (AIVs) and different avian paramyxoviruses (APMVs) in the region's waterfowl bird populations. Here, we report the results of monitoring these viruses in the wild waterfowl of the western coast of the middle Caspian Sea from 2017 to 2020. Samples from 1438 individuals of 26 bird species of 7 orders were collected, from which 21 strains of AIV were isolated, amounting to a 1.46% isolation rate of the total number of samples analyzed (none of these birds exhibited external signs of disease). The following subtypes were determined and whole-genome nucleotide sequences of the isolated strains were obtained: H1N1 (n = 2), H3N8 (n = 8), H4N6 (n = 2), H7N3 (n = 2), H8N4 (n = 1), H10N5 (n = 1), and H12N5 (n = 1). No high pathogenicity influenza virus H5 subtype was detected. Phylogenetic analysis of AIV genomes did not reveal any specific pattern for viruses in the Caspian Sea region, showing that all segments belong to the Eurasian clades of classic avian-like influenza viruses. We also did not find the amino acid substitutions in the polymerase complex (PA, PB1, and PB2) that are critical for the increase in virulence or adaptation to mammals. In total, 23 hemagglutinating viruses not related to influenza A virus were also isolated, of which 15 belonged to avian paramyxoviruses. We were able to sequence 12 avian paramyxoviruses of three species, as follows: Newcastle disease virus (n = 4); Avian paramyxovirus 4 (n = 5); and Avian paramyxovirus 6 (n = 3). In the Russian Federation, the Newcastle disease virus of the VII.1.1 sub-genotype was first isolated from a wild bird (common pheasant) in the Caspian Sea region. The five avian paramyxovirus 4 isolates obtained belonged to the common clade in Genotype I, whereas phylogenetic analysis of three isolates of Avian paramyxovirus 6 showed that two isolates, isolated in 2017, belonged to Genotype I and that an isolate identified in 2020 belonged to Genotype II. The continued regular monitoring of AIVs and APMVs, the obtaining of data on the biological properties of isolated strains, and the accumulation of information on virus host species will allow for the adequate planning of epidemiological measures, suggest the most likely routes of spread of the virus, and assist in the prediction of the introduction of the viruses in the western coastal region of the middle Caspian Sea.

Genetic Diversity of the Human Adenovirus C Isolated from Hospitalized Children in Russia (2019-2022).

The human adenovirus (HAdV) is a common pathogen in children that can cause acute respiratory virus infection (ARVI). However, the molecular epidemiological and clinical information relating to HAdV among hospitalized children with ARVI is rarely reported in Russia. A 4-year longitudinal (2019-2022) study among hospitalized children (0-17 years old) with ARVI in Novosibirsk, Russia, was conducted to evaluate the epidemiological and molecular characteristics of HAdV. Statistically significant differences in the detection rates of epidemiological and virological data of all positive viral detections of HAdV were analyzed using a two-tailed Chi-square test. The incidence of HAdV and other respiratory viruses such as human influenza A and B viruses, respiratory syncytial virus, coronavirus, parainfluenza virus, metapneumovirus, rhinovirus, bocavirus, and SARS-CoV-2 was investigated among 3190 hospitalized children using real-time polymerase chain reaction. At least one of these respiratory viruses was detected in 74.4% of hospitalized cases, among which HAdV accounted for 4%. A total of 1.3% co-infections with HAdV were also registered. We obtained full-genome sequences of 12 HAdVs, which were isolated in cell cultures. Genetic analysis revealed the circulation of adenovirus of genotypes C1, C2, C5, C89, and 108 among hospitalized children in the period from 2019-2022.

Highly Pathogenic Avian Influenza A(H5N1) Virus-Induced Mass Death of Wild Birds, Caspian Sea, Russia, 2022.

In May 2022, we observed a substantial die-off of wild migratory waterbirds on Maliy Zhemchuzhniy Island in the Caspian Sea, Russia. The deaths were caused by highly pathogenic avian influenza A(H5N1) clade 2.3.4.4.b virus. Continued surveillance of influenza viruses in wild bird populations is needed to predict virus spread over long distances.

The Development of the SARS-CoV-2 Epidemic in Different Regions of Siberia in the 2020-2022 Period.

The comparison of the development of the SARS-CoV-2 epidemic in several neighboring regions can help researchers to assess the risks and develop more effective strategies and approaches in the field of preventive medicine. We analyzed the infection and mortality statistics for the 2020-2022 period in ten individual regions of the Siberian Federal District of Russia. We also sequenced complete genomes, which allowed us to analyze the genetic diversity of SARS-CoV-2 circulated in each of the ten regions and to build a phylogenetic dendrogram for the virus variants. The ParSeq v.1.0 software was developed to automate and speed up the processing and analysis of viral genomes. At the beginning of the pandemic, in the first two waves, the B.1.1 variant (20B) dominated in all regions of the Siberian Federal District. The third and fourth waves were caused by the Delta variant. Mortality during this period was at a maximum; the incidence was quite high, but the number of deposited genomes with GISAID during this period was extremely low. The maximum incidence was at the beginning of 2022, which corresponds to the arrival of the Omicron variant in the region. The BA.5.2 variant became the dominant one. In addition, by using NextClade, we identified three recombinants in the most densely populated areas.

Does Avian Coronavirus Co-Circulate with Avian Paramyxovirus and Avian Influenza Virus in Wild Ducks in Siberia?

Avian coronaviruses (ACoV) have been shown to be highly prevalent in wild bird populations. More work on avian coronavirus detection and diversity estimation is needed for the breeding territories of migrating birds, where the high diversity and high prevalence of Orthomyxoviridae and Paramyxoviridae have already been shown in wild birds. In order to detect ACoV RNA, we conducted PCR diagnostics of cloacal swab samples from birds, which we monitored during avian influenza A virus surveillance activities. Samples from two distant Asian regions of Russia (Sakhalin region and Novosibirsk region) were tested. Amplified fragments of the RNA-dependent RNA-polymerase (RdRp) of positive samples were partially sequenced to determine the species of Coronaviridae represented. The study revealed a high presence of ACoV among wild birds in Russia. Moreover, there was a high presence of birds co-infected with avian coronavirus, avian influenza virus, and avian paramyxovirus. We found one case of triple co-infection in a Northern Pintail (Anas acuta). Phylogenetic analysis revealed the circulation of a Gammacoronavirus species. A Deltacoronavirus species was not detected, which supports the data regarding the low prevalence of deltacoronaviruses among surveyed bird species.

Changes in the Etiology of Acute Respiratory Infections among Children in Novosibirsk, Russia, between 2019 and 2022: The Impact of the SARS-CoV-2 Virus.

A wide range of human respiratory viruses are known that may cause acute respiratory infections (ARIs), such as influenza A and B viruses (HIFV), respiratory syncytial virus (HRSV), coronavirus (HCoV), parainfluenza virus (HPIV), metapneumovirus (HMPV), rhinovirus (HRV), adenovirus (HAdV), bocavirus (HBoV), and others. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COronaVIrus Disease (COVID) that lead to pandemic in 2019 and significantly impacted on the circulation of ARIs. The aim of this study was to analyze the changes in the epidemic patterns of common respiratory viruses among children and adolescents hospitalized with ARIs in hospitals in Novosibirsk, Russia, from November 2019 to April 2022. During 2019 and 2022, nasal and throat swabs were taken from a total of 3190 hospitalized patients 0-17 years old for testing for HIFV, HRSV, HCoV, HPIV, HMPV, HRV, HAdV, HBoV, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by real-time PCR. The SARS-CoV-2 virus dramatically influenced the etiology of acute respiratory infections among children and adolescents between 2019 and 2022. We observed dramatic changes in the prevalence of major respiratory viruses over three epidemic research seasons: HIFV, HRSV, and HPIV mainly circulated in 2019-2020; HMPV, HRV, and HCoV dominated in 2020-2021; and HRSV, SARS-CoV-2, HIFV, and HRV were the most numerous agents in 2021-2022. Interesting to note was the absence of HIFV and a significant reduction in HRSV during the 2020-2021 period, while HMPV was absent and there was a significant reduction of HCoV during the following epidemic period in 2021-2022. Viral co-infection was significantly more frequently detected in the 2020-2021 period compared with the other two epidemic seasons. Certain respiratory viruses, HCoV, HPIV, HBoV, HRV, and HAdV, were registered most often in co-infections. This cohort study has revealed that during the pre-pandemic and pandemic periods, there were dramatic fluctuations in common respiratory viruses registered among hospitalized patients 0-17 years old. The most dominant virus in each research period differed: HIFV in 2019-2020, HMPV in 2020-2021, and HRSV in 2021-2022. Virus-virus interaction was found to be possible between SARS-CoV-2 and HRV, HRSV, HAdV, HMPV, and HPIV. An increase in the incidence of COVID-19 was noted only during the third epidemic season (January to March 2022).

Virological and Genetic Characterization of the Unusual Avian Influenza H14Nx Viruses in the Northern Asia.

Wild aquatic birds are generally identified as a natural reservoir of avian influenza viruses (AIVs), where a high diversity of subtypes has been detected. Some AIV subtypes are considered to have relatively low prevalence in wild bird populations. Six-year AIV surveillance in Siberia revealed sporadic cases of the rarely identified H14-subtype AIV circulation. Complete genome sequencing of three H14 isolates were performed, and the analysis indicated interconnections between low pathogenic avian influenza (LPAI) viruses. We conducted hemagglutination inhibition and virus neutralization assays, estimated the susceptibility of isolates to neuraminidase inhibitors, and characterized receptor specificity. Our study revealed circulation of a new H14N9 subtype described for the first time. However, the low prevalence of the H14-subtype AIV population may be the reason for the underestimation of the diversity of H14-subtype AIVs. According to the available data, a region in which H14-subtype viruses were detected several times in 2007-2022 in the Eastern Hemisphere is Western Siberia, while the virus was also detected once in South Asia (Pakistan). Phylogenetic analysis of HA segment sequences revealed the circulation of two clades of H14-subtype viruses originated from initial 1980s Eurasian clade; the first was detected in Northern America and the second in Eurasia.

Virological and genetic characteristics of human respiratory syncytial viruses isolated in Russia, 2017-2018.

Isolation of human respiratory syncytial virus (HRSV) from clinical samples and storage of isolates for long period remains a considerable problem. We describe in detail the optimized conditions of HRSV isolation and cultivation in three cell cultures HeLa, HEp-2, and Vero. HRSV was detected in 35.2% (166/471) specimens by real-time PCR from symptomatic infants and children up to 15 years from October 2017 to March 2018 in Russia. HRSV-positive samples were used for virus isolation in HeLa, HEp-2, and Vero cells in different manners (in monolayer or suspension). To optimize the conditions of HRSV cultivation, these cell cultures were treated or not with receptor-destroying enzyme (RDE). Ten isolates were successfully obtained by the way of infection of the suspension of cells with subsequent RDE treatment. Among them, several isolates induced the cytopathogenic effect (CPE) by the syncytium formation in both Hela and HEp-2 cell cultures. The genetic analysis revealed that the manners of isolation by using monolayer or suspension and subsequent RDE treatment did not influence the nucleotide and amino acid structures of obtained HRSVs. The CPE characteristics of obtained viruses were the same in HeLa, HEp-2, and Vero cell cultures, and were described as large syncytium up to 150 microns or more in size with the nuclei peripheral location and an optically bright zone in the center of the formation. We showed that infection of cell suspension with the subsequent RDE treatment increased the chance of HRSVs isolation from clinical samples.

Detection of coronaviruses in insectivorous bats of Fore-Caucasus, 2021.

Coronaviruses (CoVs) pose a huge threat to public health as emerging viruses. Bat-borne CoVs are especially unpredictable in their evolution due to some unique features of bat physiology boosting the rate of mutations in CoVs, which is already high by itself compared to other viruses. Among bats, a meta-analysis of overall CoVs epizootiology identified a nucleic acid observed prevalence of 9.8% (95% CI 8.7-10.9%). The main objectives of our study were to conduct a qPCR screening of CoVs' prevalence in the insectivorous bat population of Fore-Caucasus and perform their characterization based on the metagenomic NGS of samples with detected CoV RNA. According to the qPCR screening, CoV RNA was detected in 5 samples, resulting in a 3.33% (95% CI 1.1-7.6%) prevalence of CoVs in bats from these studied locations. BetaCoVs reads were identified in raw metagenomic NGS data, however, detailed characterization was not possible due to relatively low RNA concentration in samples. Our results correspond to other studies, although a lower prevalence in qPCR studies was observed compared to other regions and countries. Further studies should require deeper metagenomic NGS investigation, as a supplementary method, which will allow detailed CoV characterization.

Detection of New H5N1 High Pathogenicity Avian Influenza Viruses in Winter 2021-2022 in the Far East, Which Are Genetically Close to Those in Europe.

Many high pathogenicity avian influenza (HPAI) cases in wild birds due to H5N1 HPAI virus (HPAIV) infection were reported in northern Japan in the winter of 2021-2022. To investigate the epidemiology of HPAIVs brought to Japan from surrounding areas, a genetic analysis of H5 HPAIVs isolated in northern Japan was performed, and the pathogenicity of the HPAIV in chickens was assessed by experimental infection. Based on the genetic analysis of the hemagglutinin gene, pathogenic viruses detected in northern Japan as well as one in Sakhalin, the eastern part of Russia, were classified into the same subgroup as viruses prevalent in Europe in the same season but distinct from those circulating in Asia in winter 2020-2021. High identities of all eight segment sequences of A/crow/Hokkaido/0103B065/2022 (H5N1) (Crow/Hok), the representative isolates in northern Japan in 2022, to European isolates in the same season could also certify the unlikeliness of causing gene reassortment between H5 HPAIVs and viruses locally circulating in Asia. According to intranasal challenge results in six-week-old chickens, 50% of the chicken-lethal dose of Crow/Hok was calculated as 104.5 times of the 50% egg-infectious dose. These results demonstrated that the currently prevalent H5 HPAIVs could spread widely from certain origins throughout the Eurasian continent, including Europe and the Far East, and implied a possibility that contagious viruses are gathered in lakes in the northern territory via bird migration. Active monitoring of wild birds at the global level is essential to estimate the geographical source and spread dynamics of HPAIVs.

Genomic and Epidemiological Features of COVID-19 in the Novosibirsk Region during the Beginning of the Pandemic.

In this retrospective, single-center study, we conducted an analysis of 13,699 samples from different individuals obtained from the Federal Research Center of Fundamental and Translational Medicine, from 1 April to 30 May 2020 in Novosibirsk region (population 2.8 million people). We identified 6.49% positive for SARS-CoV-2 cases out of the total number of diagnostic tests, and 42% of them were from asymptomatic people. We also detected two asymptomatic people, who had no confirmed contact with patients with COVID-19. The highest percentage of positive samples was observed in the 80+ group (16.3%), while among the children and adults it did not exceed 8%. Among all the people tested, 2423 came from a total of 80 different destinations and only 27 of them were positive for SARS-CoV-2. Out of all the positive samples, 15 were taken for SARS-CoV-2 sequencing. According to the analysis of the genome sequences, the SARS-CoV-2 variants isolated in the Novosibirsk region at the beginning of the pandemic belonged to three phylogenetic lineages according to the Pangolin classification: B.1, B.1.1, and B.1.1.129. All Novosibirsk isolates contained the D614G substitution in the Spike protein, two isolates werecharacterized by an additional M153T mutation, and one isolate wascharacterized by the L5F mutation.

Genetics of Japanese H5N8 high pathogenicity avian influenza viruses isolated in winter 2020-2021 and their genetic relationship with avian influenza viruses in Siberia.

In winter 2020-2021, Japan experienced multiple serious outbreaks of H5N8 high pathogenicity avian influenza (HPAI)-52 outbreaks at poultry farms and 58 cases in wild birds or the environment-that occurred simultaneously with outbreaks in Europe. Here, we examined how the H5N8 HPAI viruses (HPAIVs) emerged and spread through Japan and across the Eurasian continent. Phylogenetic and phylogeographic analyses were performed using full genetic sequences of the viruses that caused 52 outbreaks at poultry farms or were isolated from 11 infected wild birds. Genetically, the viruses showed five genotypes (E1, E2, E3, E5 and E7) that have already been reported in Korea. The viruses showing the E3 genotype were found to have caused most of the HPAI outbreaks at poultry farms and were detected over the longest period of time. The internal genes of the viruses were genetically related to those of AIVs isolated through avian influenza surveillance activities in regions of Siberia including Buryatia, Yakutia and Amur regions, suggesting that the Japanese viruses emerged via reassortment events with AIVs genetically related to Siberian AIVs. In addition, H5N2 and H5N8 HPAIVs were isolated from wild birds during surveillance activities conducted in the Novosibirsk region of Siberia in summer 2020. Phylogenetic analyses revealed that these viruses possessed haemagglutinin genes that were related to those of H5N8 HPAIVs that were circulating in Europe in winter 2020-2021. These results suggest that the viruses in wild birds during summer in Siberia most likely spread in both Asia and Europe the following winter. Together, the present results emphasize the importance of continual monitoring of AIVs in Siberia for forecasting outbreaks not only in Asia but also further away in Europe.

Anti-Influenza Activity of Medicinal Material Extracts from Qinghai-Tibet Plateau.

To discover sources for novel anti-influenza drugs, we evaluated the antiviral potential of nine extracts from eight medicinal plants and one mushroom (Avena sativa L., Hordeum vulgare Linn. var. nudum Hook. f., Hippophae rhamnoides Linn., Lycium ruthenicum Murr., Nitraria tangutorum Bobr., Nitraria tangutorum Bobr. by-products, Potentilla anserina L., Cladina rangiferina (L.) Nyl., and Armillaria luteo-virens) from the Qinghai-Tibetan plateau against the influenza A/H3N2 virus. Concentrations lower than 125 µg/mL of all extracts demonstrated no significant toxicity in MDCK cells. During screening, seven extracts (A. sativa, H. vulgare, H. rhamnoides, L. ruthenicum, N. tangutorum, C. rangiferina, and A. luteo-virens) exhibited antiviral activity, especially the water-soluble polysaccharide from the fruit body of the mushroom A. luteo-virens. These extracts significantly reduced the infectivity of the human influenza A/H3N2 virus in vitro when used at concentrations of 15.6-125 µg/mL. Two extracts (N. tangutorum by-products and P. anserina) had no A/H3N2 virus inhibitory activity. Notably, the extract obtained from the fruits of N. tangutorum and N. tangutorum by-products exhibited different anti-influenza effects. The results suggest that extracts of A. sativa, H. vulgare, H. rhamnoides, L. ruthenicum, N. tangutorum, C. rangiferina, and A. luteo-virens contain substances with antiviral activity, and may be promising sources of new antiviral drugs.

Highly Pathogenic Avian Influenza A(H5N8) Virus Clade 2.3.4.4b, Western Siberia, Russia, 2020.

Two variants of highly pathogenic avian influenza A(H5N8) virus were detected in dead poultry in Western Siberia, Russia, during August and September 2020. One variant was represented by viruses of clade 2.3.4.4b and the other by a novel reassortant between clade 2.3.4.4b and Eurasian low pathogenicity avian influenza viruses circulating in wild birds.

Biological Properties and Genetic Characterization of Novel Low Pathogenic H7N3 Avian Influenza Viruses Isolated from Mallard Ducks in the Caspian Region, Dagestan, Russia.

Avian influenza viruses (AIVs) are maintained in wild bird reservoirs, particularly in mallard ducks and other waterfowl. Novel evolutionary lineages of AIV that arise through genetic drift or reassortment can spread with wild bird migrations to new regions, infect a wide variety of resident bird species, and spillover to domestic poultry. The vast continental reservoir of AIVs in Eurasia harbors a wide diversity of influenza subtypes, including both highly pathogenic (HP) and low pathogenic (LP) H7 AIV. The Caspian Sea region is positioned at the intersection of major migratory flyways connecting Central Asia, Europe, the Black and Mediterranean Sea regions and Africa and holds a rich wetland and avian ecology. To understand genetic reservoirs present in the Caspian Sea region, we collected 559 cloacal swabs from Anseriformes and other species during the annual autumn migration periods in 2017 and 2018. We isolated two novel H7N3 LPAIV from mallard ducks whose H7 hemagglutinin (HA) gene was phylogenetically related to contemporaneous strains from distant Mongolia, and more closely Georgia and Ukraine, and predated the spread of this H7 LPAIV sublineage into East Asia in 2019. The N3 neuraminidase gene and internal genes were prototypical of AIV widely dispersed in wild bird reservoirs sampled along flyways connected to the Caspian region. The polymerase and nucleoprotein segments clustered with contemporaneous H5 HPAI (clade 2.3.4.4b) isolates, suggesting the wide dispersal of H7 LPAIV and the potential of this subtype for reassortment. These findings highlight the need for deeper surveillance of AIV in wild birds to better understand the extent of infection spread and evolution along spatial and temporal flyways in Eurasia.

Experimental Infection Using Mouse-Adapted Influenza B Virus in a Mouse Model.

Every year, influenza B viruses (IBVs) contribute to annual illness, and infection can lead to serious respiratory disease among humans. More attention is needed in several areas, such as increasing virulence or pathogenicity of circulating B viruses and developing vaccines against current influenza. Since preclinical trials of anti-influenza drugs are mainly conducted in mice, we developed an appropriate infection model, using an antigenically-relevant IBV strain, for furtherance of anti-influenza drug testing and influenza vaccine protective efficacy analysis. A Victoria lineage (clade 1A) IBV was serially passaged 17 times in BALB/c mice, and adaptive amino acid substitutions were found in hemagglutinin (HA) (T214I) and neuraminidase (NA) (D432N). By electron microscopy, spherical and elliptical IBV forms were noted. Light microscopy showed that mouse-adapted IBVs caused influenza pneumonia on day 6 post inoculation. We evaluated the illness pathogenicity, viral load, and histopathological features of mouse-adapted IBVs and estimated anti-influenza drugs and vaccine efficiency in vitro and in vivo. Assessment of an investigational anti-influenza drug (oseltamivir ethoxysuccinate) and an influenza vaccine (Ultrix®, SPBNIIVS, Saint Petersburg, Russia) showed effectiveness against the mouse-adapted influenza B virus.

Characterization and Phylodynamics of Reassortant H12Nx Viruses in Northern Eurasia.

Wild waterfowl birds are known to be the main reservoir for a variety of avian influenza viruses of different subtypes. Some subtypes, such as H2Nx, H8Nx, H12Nx, and H14Nx, occur relatively rarely in nature. During 10-year long-term surveillance, we isolated five rare H12N5 and one H12N2 viruses in three different distinct geographic regions of Northern Eurasia and studied their characteristics. H12N2 from the Far East region was a double reassortant containing hemagglutinin (HA), non-structural (NS) and nucleoprotein (NP) segments of the American lineage and others from the classical Eurasian avian-like lineage. H12N5 viruses contain Eurasian lineage segments. We suggest a phylogeographical scheme for reassortment events associated with geographical groups of aquatic birds and their migration flyways. The H12N2 virus is of particular interest as this subtype has been found in common teal in the Russian Far East region, and it has a strong relation to North American avian influenza virus lineages, clearly showing that viral exchange of segments between the two continents does occur. Our results emphasize the importance of Avian Influenza Virus (AIV) surveillance in Northern Eurasia for the annual screening of virus characteristics, including the genetic constellation of rare virus subtypes, to understand the evolutionary ecology of AIV.

Novel reassortant of H1N1 swine influenza virus detected in pig population in Russia.

Pigs play an important role in interspecies transmission of the influenza virus, particularly as "mixing vessels" for reassortment. Two influenza A/H1N1 virus strains, A/swine/Siberia/1sw/2016 and A/swine/Siberia/4sw/2017, were isolated during a surveillance of pigs from private farms in Russia from 2016 to 2017. There was a 10% identity difference between the HA and NA nucleotide sequences of isolated strains and the most phylogenetically related sequences (human influenza viruses of 1980s). Simultaneously, genome segments encoding internal proteins were found to be phylogenetically related to the A/H1N1pdm09 influenza virus. In addition, two amino acids (129-130) were deleted in the HA of A/swine/Siberia/4sw/2017 compared to that of A/swine/Siberia/1sw/2016 HA.

Pathology of A(H5N8) (Clade 2.3.4.4) Virus in Experimentally Infected Chickens and Mice.

The emergence of novel highly pathogenic avian influenza viruses (HPAIVs) in migratory birds raises serious concerns as these viruses have the potential to spread during fall migration. We report the identification of novel HPAIV A(H5N8) clade 2.3.4.4 virus that was isolated from sick domestic duck at commercial farm during the second wave of spread that began in October and affected poultry (ducks; chiсkens) in several European regions of Russia and Western Siberia in 2016. The strain was highly lethal in experimental infection of chickens and mice with IVPI = 2.34 and MLD50 = 1.3log10⁡ EID50, accordingly. Inoculation of chickens with the HPAIV A/H5N8 demonstrated neuroinvasiveness, multiorgan failure, and death of chickens on the 3rd day post inoculation. Virus replicated in all collected organ samples in high viral titers with the highest titer in the brain (6.75±0.1 log10TCID50/ml). Effective virus replication was found in the following cells: neurons and glial cells of a brain; alveolar cells and macrophages of lungs; epithelial cells of a small intestine; hepatocytes and Kupffer cells of a liver; macrophages and endothelial cells of a spleen; and the tubular epithelial cells of kidneys. These findings advance our understanding of histopathological effect of A(H5N8) HPAIV infection.