Coinfection of parvovirus and astrovirus in gout-affected goslings

Development of a chicken egg yolk antibody (IgY) could effectively prevent and treat goose astrovirus infection

Goose astrovirus (GAstV) is a major threat to the goose industry, with no effective drugs or vaccines available. Developing safe and effective prevention and treatment strategies is essential to reduce its impact. In our study, we used the GAstV GDCS strain as the vaccine antigen and found that a 1 ‰ formaldehyde concentration effectively inactivated the virus after 24 h at 37 °C. The inactivated virus antigen was subsequently emulsified with white oil to formulate the GAstV inactivated vaccine. This vaccine was administered four times to 22-week-old laying hens, and IgY was subsequently purified from the egg yolk using the polyethylene glycol (PEG) precipitation method. After the fourth immunization, IgY concentration was 3.133 mg/mL. SDS-PAGE showed IgY has a 65 kDa heavy chain and a 25 kDa light chain. The IgY effectively neutralized GAstV in vitro with a titer of up to 2^9.67. Administering IgY to goslings effectively prevents and treats GAstV infection by reducing symptoms, mortality, tissue damage, and viral load. These findings offer significant tools for the clinical prevention and management of GAstV infection.

Rapid detection of avipoxvirus using a fluorescent probe-based multienzyme isothermal amplification assay

Avipoxvirus (APV) is a prevalent DNA virus in avian species, causing clinical symptoms of fowlpox and leading to reduced egg production, slower broiler growth, and increased mortality. The spread of APV poses a significant threat to the global poultry industry, potentially causing substantial economic losses. Effective control of APV, particularly its major species such as fowlpoxvirus and pigeonpoxvirus, requires the development of rapid and specific diagnostic tools. In this study, a novel multi-enzyme isothermal rapid amplification (MIRA) assay was developed to detect APV. Various primer-probe combinations were screened to identify an optimal pair targeting a conserved region of the viral P4b gene. The MIRA assay operates at a constant temperature and results can be visualized through fluorescence signal detection. The sensitivity, specificity, and applicability of the MIRA assay were evaluated. Additionally, 86 clinical samples were tested to assess the accuracy of the MIRA assay. The MIRA assay provides results within 15 minutes demonstrated high specificity, with no cross-reactivity with other avian pathogens. It achieved a detection limit of 50 copies/μl, which is consistent with the qPCR assay. Further evaluation with 86 clinical samples showed that the accuracy of the MIRA assay was comparable to that of qPCR in detecting fowlpoxvirus and pigeonpoxvirus. The results highlight the convenience, sensitivity, and rapidity of the MIRA assay as a promising tool for diagnosing APV.

Isolation, Characterization, and Comparative Analysis of Two Subtypes of Goose Astrovirus in Guangdong Province, China

Since 2017, an infectious disease characterized by gosling gout and caused by goose astrovirus (GAstV) has affected geese in most major goose-producing regions of China. In this study, a total of 385 geese displaying gout symptoms were sampled from 12 cities in Guangdong Province, China, between 2019 and 2021. RT-PCR analysis revealed that all samples were positive for GAstV (385/385), with GAstV-II being the predominant subtype, accounting for 90.4% (348/385) of the cases. Co-infection with GAstV-I and GAstV-II was detected in 50.4% (194/385) of the samples. Additionally, different GAstV subtypes were successfully isolated using goose embryos, namely GDYJ-21-01 (GAstV-I) and GDZJ-21-01 (GAstV-II). Analysis of viral copy numbers in major pathological tissues following infection of goslings and goose embryos revealed that GDZJ strain exhibited broader tissue tropism than GDYJ strain. Compared to other tissues, GDYJ strain displayed tissue tropism exclusively in the cecal tonsils of goslings and the allantoic fluid of embryos. Structural prediction and alignment using AlphaFold 2.0 identified an α-helix in the S223-A226 region of the GDZJ VP34 protein, while a loop structure was observed in the Q235-Q237 region of the corresponding GDYJ VP34 protein. Furthermore, although the VP27 protein regions of both subtypes contained five β-sheet structures, the overall sequence similarity was relatively low, at 37.1%. This study broadens our understanding of the prevalence differences among GAstV subtypes and provides valuable insights into the development of reagents for preventing these viral infections.

Isolation, identification, whole genome sequence analysis, and pathogenicity of a potential recombinant goose parvovirus

Goose parvovirus (GPV) is the etiological agent responsible for gosling plague (GP), which is an acute hemorrhagic infectious disease affecting geese, posing significant economic challenges to the poultry industry. Furthermore, recent studies have identified that the novel goose parvovirus (NGPV), a recombinant variant of the classic GPV, is responsible for duck short beak dwarfism syndrome, which has significantly affected duck farm. Therefore, the infection and genetic evolution of GPV have attracted widespread attention of researchers in poultry disease. In order to clarify the prevalence and genetic evolution of clinically severe GPV in the Heilongjiang region, this study successfully isolated a strain of GPV HLJ2023 from goose embryos, which results in the mortality rate of 100 % after 5 generations. The electron microscope shows that the virus particles are spherical, with a diameter of approximately 28 nm, and HLJ2023 strain has a total genome length of 5048 nt. SimPlot analysis showed that HLJ2023 strain is closely related to duck parvovirus and NGPV in the VP3 gene region. Recombination analysis showed that the isolated strain is a potential recombinant of the NGPV JS191021 strain and the GMD (Goose parvovirus hosted by Muscovy duck) PT strain. the strong pathogenicity of HLJ2023 strain to goslings. 36 h after the challenge, the goslings were depressed and had a mortality rate up to 100 %. Autopsy revealed intestinal bleeding, thinning of the intestinal wall, and a large amount of fibrous clots and fragments in the intestinal cavity. This study isolated a highly pathogenic potential recombinant GPV, further expanding the genetic evolution and pathogenicity information of avian parvovirus. At the same time, the isolated strain provides a candidate strain for the development of biological products for treating GPV.

Goose parvovirus, goose hemorrhagic polyomavirus and goose circovirus infections are prevalent in commercial geese flocks in Poland and contribute to overall health and production outcomes: a two-year observational study

BACKGROUND

The intensification of poultry production and the constantly growing number of geese flocks in Poland increases the risk of infectious diseases. The study aimed to determine the health status of commercial geese, with particular emphasis on infections with goose parvovirus (GPV), goose circovirus and goose hemorrhagic polyomavirus. The study monitored 27 geese flocks, ranging in size from 3,000 to 13,000 birds, over a two-year period.

RESULTS

The results showed the presence of genetic material GPV in all flocks tested, whereas GoCV and GHPV were detected in some flocks, 44.4% and 59.3% respectively. A significant number of flocks were found to be co-infected with two (74.1%) and three viruses (22.2%). Additionally, a phylogenetic analysis of GPV and GHPV was conducted based on a fragment of the virus genome, while for GoCV the phylogenetic analysis was performed on whole genome. Analysis of the vp1 gene revealed that 30.8% of the sequences obtained belonged to a variant of the virus known as novel GPV, so far attributed to short beak and dwarfism syndrome in Pekin ducks. The majority of the GoCV genomic sequences exhibited high homology to the Polish sequence, which was previously isolated from domestic geese. Only one sequence was found to be closely related to sequences from wild birds.

CONCLUSIONS

Our research indicates that viral and bacterial co-infections are a significant problem in flocks of geese. Rarely did a single factor have a clear impact on the health status of the flock. Typically, mixed viral infections, as well as bacterial complications (mainly Escherichia coli, less frequently Ehrysipelotrix rhusiopathiae, Gallibacterium anatis, and Salmonella Typhimurium), or fungal complications lead to an increase in mortality in the flock, growth diversification of birds, and thus a reduction in production rates.

Genome-wide transcriptome analysis of gene expression profiles in Goose Astrovirus-infected GEF cells

As a novel emerging pathogen, mainly causing visceral and articular gout in goslings, the pathogenesis of goose astrovirus (GAstV) remains unclear, seriously impeding the development of effective prevention and control methods. To better understand the reprogrammed cellular genes due to GAstV infection, a high-throughput transcriptome analysis was performed with primary goose embryo fibroblasts (GEF) at 48 h after infection. A total of 2324 differentially expressed genes (DEGs) were identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that most DEGs were closely associated with immune signal pathway and metabolic process. Subsequently, several immune and metabolic related genes, such as Mx, OAS, STAT1, IFIT5, and ADA, were identified and further validated via quantitative real-time PCR and western blot. This was the first study using GEF as the cell model to explore the host response to GAstV infection, which will undoubtedly provide a solid foundation to elucidate the pathogenesis of GAstV.

Current Situation of Goose Astrovirus in China: A Review

Gosling gout disease is an infectious disease caused by goose astrovirus (GAstV), which can result in urate deposition in the internal organs and joints of goslings. Since 2015, outbreaks of gosling gout disease have occurred in several goose-producing areas in China. Subsequently, the disease spread to the vast majority of eastern China, becoming a major threat to goose farms and causing huge economic losses to the goose industry. Meanwhile, GAstV can infect species of birds other than geese. It is worth noting that, as an emerging virus, the research on GAstV is still in the early stages. Therefore, the investigation of GAstV has become an urgent issue, which can improve understanding of GAstV and develop effective measures to control its threat to poultry. The purpose of this review is to summarize the latest research progress on GAstV in recent years, mainly focusing on the genetic evolution, pathogenesis, diagnostic detection, and control strategies of GAstV, aiming to provide a reference for scientific prevention and control of GAstV infection.

Comparative transcriptomic analysis of goose astrovirus genotype 1 and 2 in goose embryonic fibroblasts

Gout in goslings has become widespread and caused huge economic losses for the goose industry. Emerging evidence suggests that goose astrovirus (GAstV) is a prominent etiological factor of gout in goslings. At present, 2 genotypes of GAstV have been identified named GAstV-1 and GAstV-2. Here, we isolated the GAstV-1 HBLY strain and GAstV-2 XT1 strain from HeBei province of China. The genome and proliferation characteristics of GAstV-1 and GAstV-2 were analyzed and the results showed that the whole genome identity was 53.8% to 55.8%, especially the nucleotide and amino acids identity of ORF2 and Cap protein was only 49.5% to 50.5% and 19.6% to 22.6 %. Interestingly, GAstV-1 and GAstV-2 with such low homology both can cause gout in goslings. To further explore this phenomenon, the whole genomic expression profile of goose embryonic fibroblasts (GEFs) infected with GAstV-1 was investigated in comparison with GAstV-2. The results revealed that 126 differentially expressed genes (DEGs) were identified between GAstV-1-infected and uninfected cells at 48 h postinfection (hpi), and 262 DEGs between GAstV-2 and uninfected. Among these, there are 15 commonly up-regulated genes and 19 commonly down-regulated genes. Gene ontology (GO) enrichment analysis, Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, and short time-series expression miner (STEM) analysis suggested that GAstV-1 can induce a higher innate immune response to GEFs, while GAstV-2 has a more pronounced effect on GEFs metabolic pathways. The transcriptomic analysis results significantly enhance our comprehension of the pathogenic mechanisms of GAstV.

Development of a multienzyme isothermal and lateral flow dipstick combination assay for the rapid detection of goose astrovirus II

Introduction

Goose astrovirus (GAstV) is a newly emerging pathogen that is currently widespread among geese, causing visceral gout and leading to substantial gosling mortalities, posing a severe threat to the waterfowl industry. GAstV II is the predominant epidemic strain, characterized by its high morbidity and mortality rate. Consequently, there is an urgent necessity to develop an effective diagnostic approach to control the dissemination of GAstV II, particularly in clinical farms with limited laboratory resources.

Methods

In this study, a novel multi-enzyme isothermal rapid amplification (MIRA) and lateral flow dipstick (LFD) combined assay was developed. Different primers designed specific targeting a highly conserved region within the viral RdRp gene for the detection of GAstV II. Primers optimized and MIRA-LFD assay analyzed its performance regarding limits of detection, specificity, and efficiency of detection.

Results

The developed MIRA amplification is conducted at a constant temperature and accomplished within 10 minutes. Subsequent naked-eye observation of the LFD strips merely takes 5 minutes. The established MIRA-LFD method exhibits high specificity, with no cross-reaction with other pathogens and attains a detection sensitivity of 1 copy/μl, which is consistent with the reverse transcription quantitative PCR (RT-qPCR) assay. Further evaluation with clinical samples indicates that the accuracy of this MIRA-LFD method correlates well with RT-qPCR for the detection of GAstV II.

Conclusion

In summary, the convenience, sensitivity, and rapidity of this newly developed detection method offer a significant advantage for on-site diagnosis of GAstV II.

Molecular characterization of a virulent goose astrovirus genotype-2 with high mortality in vitro and in vivo

Goose astrovirus (GAstV) is a newly identified viral pathogen threatening waterfowl, exhibiting a high prevalence across various regions in China. Notably, the Guanghan District of Deyang City, situated in Sichuan Province, has faced a outbreak of GAstV, resulting in significant mortality among goslings due to the induction of gout-like symptoms. In our research, we successfully isolated a GAstV strain known as GAstV SCG3. This strain exhibits efficient replication capabilities, proving virulent in goslings and goose embryos. Our study delved into the characteristics of GAstV SCG3 both in vitro and in vivo. Additionally, we examined tissue phagocytosis and the distribution of GAstV SCG3 in deceased goslings using H&E staining and IHC techniques. According to the classification established by the ICTV, GAstV SCG3 falls under the category of GAstV genotype-2. Notably, it demonstrates the highest homology with the published AHAU5 sequences, reaching an impressive 98%. Furthermore, our findings revealed that GAstV SCG3 exhibits efficient proliferation exclusively in goose embryos and in LMH cells, while not manifesting in seven other types of avian and mammalian cells. Significantly, the mortality of GAstV on goslings and goose embryos are 93.1 and 80%, respectively. Moreover, the viral load in the livers of infected goslings surpasses that in the kidneys when compared with the attenuated strain GAstV SCG2. The mortality of GAstV is usually between 20% and 50%, our study marks the first report of a virulent GAstV strain with such a high mortality.

Molecular epidemiology and virulence of goose astroviruses genotype-2 with different internal gene sequences

Goose astrovirus (GAstV) is a small, non-enveloped, single-stranded, positive-sense RNA virus. GAstV has rapidly spread across various regions in China since 2016. In Sichuan, out of 113 samples were collected from goose diseases between 2019 and 2022, 97 were positive for GAstV through PCR testing. Remarkably, over the past three years, GAstV outbreak in Sichuan has accounted for an astonishing 85.8% of all goose-origin viruses. Among these cases, 63.9% had single GAstV infections, 29.9% had dual infections, and 6.2% had quadruple infections. To comprehend the variations in virulence among distinct strains of GAstV. 12 representative strains of single GAstV infections were isolated. These strains exhibited distinct characteristics, such as prominent white urate depositions in organs and joints, as well as extensive tissues phagocytosis in major target organs' tissues. The conserved ORF1b genes and the variable ORF2 genes of these representative GAstV strains were sequenced, enabling the establishment of phylogenetic trees for GAstV. All GAstV strains were identified as belonging to genotype-2 with varying internal gene sequences. Experiments were conducted on GAstV genotype-2, both in vivo and in vitro, revealed significant variations in pathogenicity and virulence across susceptible cells, embryos, and goslings. This comprehensive study enhances researchers' understanding of the transmission characteristics and virulence of GAstV genotype-2, aiding in a better comprehension of their molecular epidemiology and pathogenic mechanism.

Global analysis of gene expression profiles and gout symptoms in goslings infected with goose astrovirus

While blocking inflammation is an effective way to ease the symptoms of gout disease in humans, the treatment and prevention of gout in goslings infected with goose astrovirus (GAstV), a recently emergent condition, remain unclear. In this study, we investigated the reprogramming of the host genes as a result of GAstV infection by combining analysis of the global transcriptome and metabolic network pathways in the kidneys of goslings infected with GAstV. We showed that as GAstV replication increased in vivo, the regulation of key enzymes in the host metabolism progressively increased, flowing metabolites into the purine/pyrimidine biosynthesis pathways. Furthermore, we found that GAstV: 1) inhibits the host oxidation-reduction response by inhibiting the expression of the catalase gene; 2) activates the Toll-like receptor 2 pathway to enhance the immune inflammatory response; and 3) activates the key enzyme in lactic acid synthesis to produce lactate accumulation which inhibits the host's antiviral response, so as to facilitate the replication of the virus itself. This study provided the first insight into the overall metabolic requirements of GAstV for replication in vivo by combining transcriptome with metabolic network pathway information.

Insertion of exogenous genes within the ORF1b coding region of porcine astrovirus

Porcine astrovirus (PAstV) is a common cause of diarrhea in swine farms. The current understanding of the molecular virology and pathogenesis of PAstV is incomplete, especially due to the limited functional tools available. Here, ten sites in the open reading frame 1b (ORF1b) of the PAstV genome were determined to tolerate random 15 nt insertions based on the infectious full-length cDNA clones of PAstV using transposon-based insertion-mediated mutagenesis of three selected regions of the PAstV genome. Insertion of the commonly used Flag tag into seven of the ten insertion sites allowed the production of infectious viruses and allowed their recognition by specifically labeled monoclonal antibodies. Indirect immunofluorescence showed that the Flag-tagged ORF1b protein partially overlapped with the coat protein within the cytoplasm. An improved light-oxygen-voltage (iLOV) gene was also introduced into these seven sites, and only one viable recombinant virus that expressed the iLOV reporter gene at the B2 site was recovered. Biological analysis of the reporter viruses showed that these exhibited similar growth characteristics to the parental virus, but they produced fewer infectious virus particles and replicated at a slower rate. The recombinant viruses containing iLOV fused to ORF1b protein, which maintained their stability and displayed green fluorescence for up to three generations after passaging in cell culture. The porcine astroviruses (PAstVs) expressing iLOV were then used to assess the in vitro antiviral activities of mefloquine hydrochloride and ribavirin. Altogether, the recombinant PAstVs expressing iLOV can be used as a reporter virus tool for the screening of anti-PAstV drugs as well as the investigation of PAstV replication and the functional activities of proteins in living cells.

TaqMan-probe-based multiplex real-time RT-qPCR for simultaneous detection of GoAstV, GPV, and GoCV

Goose astrovirus (GoAstV), goose parvovirus (GPV), and goose circovirus (GoCV) infections have similar symptoms, such as severe diarrhea, and cause serious economic losses to the goose industry globally. Therefore, it is necessary to develop a rapid and accurate method for the differential diagnosis of the 3 viruses. In this study, a TaqMan probe-based multiplex reverse transcription-qualitative polymerase chain reaction (RT-qPCR) method was established and optimized for simultaneous detection of the three viruses. Three pairs of specific primers and probes were designed considering the conserved sequences of ORF2, VP3, and Rep of GoAstV, GPV, and GoCV, respectively. Singleplex real-time RT-qPCR detected a minimum of 10 copies of these genes, while multiplex real-time RT-qPCR detected a minimum of 100 copies. The correlation coefficients exceeded 0.99, and the amplification efficiency was 80 to 100%. The assay had high sensitivity, specificity, and repeatability. In 85 tissue samples, GoAstV and GPV were the main pathogens and demonstrated co-infection. This assay provides a rapid, efficient, specific, and sensitive tool for the detection of GoAstV, GPV, and GoCV. This can facilitate disease management and epidemiological surveillance.

A Review of the Emerging Poultry Visceral Gout Disease Linked to Avian Astrovirus Infection

Avian astroviruses, including chicken astrovirus (CAstV), avian nephritisvirus (ANV), and goose astrovirus (GoAstV), are ubiquitous enteric RNA viruses associated with enteric disorders in avian species. Recent research has found that infection of these astroviruses usually cause visceral gout in chicken, duckling and gosling. However, the underlying mechanism remains unknown. In the current article, we review recent discoveries of genetic diversity and variation of these astroviruses, as well as pathogenesis after astrovirus infection. In addition, we discuss the relation between avian astrovirus infection and visceral gout in poultry. Our aim is to review recent discoveries about the prevention and control of the consequential visceral gout diseases in poultry, along with the attempt to reveal the possible producing process of visceral gout diseases in poultry.

Isolation, identification, and pathogenicity of a goose astrovirus causing fatal gout in goslings

Since November 2016, severe infectious diseases characterized by gout and kidney swelling and caused by goose astrovirus (GoAstV) have affected goslings in major goose-producing areas in China. In 2021, a similar serious infectious disease broke out in commercial goose farms in Heilongjiang Province, China. In this study, strain HLJ2021 was successfully isolated from goose embryos. Electron microscopy showed that the viral particles are spherical, with a diameter of about 28 nm. The complete genomic length of strain HLJ2021 is 7210 nt, and it encodes three viral proteins. A phylogenetic analysis showed that strain HLJ2021 belongs to GoAstV-2 (G2). Compared with the two original GoAstV strains, amino acid site 540^Q of the strain HLJ2021 spike domain has a mutation that affects the protein structure. One potential recombination event occurred between strains HLJ2021 and AstV/HB01/Goose/0123/19, which led to the generation of recombinant strain AstV/HN03/Goose/0402/19. Strain HLJ2021 also showed strong pathogenicity in goslings. Goslings infected with GoAstV began to die at 48 h post-infection (hpi), with a mortality rate of 83.3% at 240 hpi. At autopsy, visceral urate deposits, severe renal hemorrhage and swelling, and urate in the ureter were observed in the dead goslings. These findings extend our understanding of the evolution of GoAstV, which causes gout. The isolated GoAstV strain HLJ2021 provides a potential resource for the development of biological products for the prevention of goose gout.

A Review of Emerging Goose Astrovirus Causing Gout

In recent years, an infection in geese caused by goose astrovirus (GAstV) has repeatedly occurred in coastal areas of China and rapidly spread to inland provinces. The infection is characterized by joint and visceral gout and is fatal. The disease has caused huge economic losses to China's goose industry. GAstV is a nonenveloped, single-stranded, positive-sense RNA virus. As it is a novel virus, there is no specific classification. Here, we review the current understanding of GAstV. The virus structure, isolation, diagnosis and detection, innate immune regulation, and transmission route are discussed. In addition, since GAstV can cause gout in goslings, the possible role of GAstV in gout formation and uric acid metabolism is discussed. We hope that this review will inform researchers to rapidly develop effective methods to prevent and treat this disease.

Goose Astrovirus in China: A Comprehensive Review

Goose astroviruses (GoAstVs) are small non-enveloped viruses with a genome consisting of a single-stranded positive-sense RNA molecule. A novel GoAstV was identified in Shandong in 2016 and quickly spread to other provinces in China, causing gout in goslings, with a mortality rate of approximately 50%. GoAstV can also cause gout in chickens and ducks, indicating its ability to cross the species barrier. GoAstV has only been reported in China, where it has caused serious losses to the goose-breeding industry. However, in view of its cross-species transmission ability and pathogenicity in chickens and ducks, GoAstV should be a concern to poultry breeding globally. As an emerging virus, there are few research reports concerning GoAstV. This review summarizes the current state of knowledge about GoAstV, including the epidemiology, evolution analysis, detection methods, pathogenicity, pathogenesis, and potential for cross-species transmission. We also discuss future outlooks and provide recommendations. This review can serve as a valuable reference for further research on GoAstV.

Extensive genetic heterogeneity and molecular characteristics of emerging astroviruses causing fatal gout in goslings

Since 2017, outbreaks of gosling astroviruses (GoAstV) causing the major symptoms related to gout in geese have posed a threat to China's poultry industry and caused huge economic losses. In this study, tissue samples from goslings with gout and urate deposition as the main symptoms were taken from 14 goose farms in different regions of China and screened for pathogen infection. The infection rate of GoAstV was 100%, whereas the infection rates of goose parvovirus, reovirus, Tembusu virus, and goose hemorrhagic polyomavirus were 2, 4, 0, and 0%, respectively. In total, 14 GoAstV strains were isolated and their complete genomes were sequenced. Based on the phylogenetic trees, the 14 isolated strains were classified as GoAstV (G-I) and were considered distant from strains belonging to GoAstV (G-II). The multiple sequence alignments indicated a tremendous amount of amino acid mutations in some parts of the encoding proteins of these strains; the main mutations were located in open reading frames (ORFs)—ORF1a and ORF2, such as M533V and F568S in ORF1a and A614T in ORF2. On the other hand, Further, 2 of the 14 GoAstV strains were possibly derived through inter-GoAstV-I recombination. Taken together, these findings indicate that GoAstVs are evolving in a more complex manner and have diverse transmission routes.

Genomic and Epidemiological Characteristics Provide Insights into the Phylogeographic Spread of Goose Astrovirus in China

Goose astrovirus (GAstV) is an emerging pathogen with a wide distribution in China that causes visceral gout and leads to significant economic losses in the goose industry. Here, 10 GAstV strains were isolated from different farms in southeast China. We performed an integrated analysis of the full-genome sequences of these new strains alongside comprehensive epidemiological surveillance information from the database. Interestingly, the results showed two distinct genotypes of GAstV, which were evolutionarily distant from each other. Group I GAstVs were closely related to DAstV IV, and group II strains were classified with duck astrovirus (DAstV) II and turkey astrovirus (TAstV) II. Further investigation showed that among the GAstV I strains, ZJC14 and AHDY differed from FLX. Comparative analysis of 58 available genomes clustered the GAstV II strains into two subgroups. We identified two major mutation sites, 456 (E/D) and 540 (L/Q), in the capsid protein, which were related to distinct subgroups according to evolution. GAstV II subgroup 1a strains are the predominant strains in the current prevalent epidemiology. Phylogeographic analysis based on 90 reported cases from 13 provinces revealed the complexity and severity of GAstV epidemics in China, within which Henan, Anhui and Jiangsu provinces have suffered great impacts. According to these phylogeographic investigations, following the initial introduction of GAstV from Hunan Province, the dispersal of GAstV with different subgenotypes on a nationwide scale may be explained by the live gosling trade. Our findings have important implications for the evolution and dispersal of GAstV and will contribute to understanding the potential risk of GAstV. This article is protected by copyright. All rights reserved.

Isolation and phylogenetic analysis of goose astrovirus type 1 from goslings with gout in Jiangxi province, China

Goose astrovirus (GoAstV) is a new Avastrovirus of the genus astrovirus causing gout, hemorrhage, and swellings of kidneys that have affected goslings around the major goose-producing regions in China. The GoAstV is divided into goose astrovirus type 1 (GoAstV-1) and goose astrovirus type 2 (GoAstV-2). Although GoAstV-2 is known to be the causative agent of goose gout, little published information about the relationship between GoAstV-1 and goose gout is unknown. In this study, we investigated the presence of GoAstV-1 in 293 visceral tissue/dead embryos samples with gout on different farms in Jiangxi province, China. A survey result indicated that the mono-infection of GoAstV-1 (32.08%) and co-infection of GoAstV-1 (12.28%) with GoAstV-2 in gout goslings in Jiangxi, China. JXGZ, a GoAstV-1 strain, was effectively isolated from the visceral tissue of gosling gout and serially propagated for more than 25 passages in a goose embryo. The JXGZ strain's whole genome was sequenced and investigated. Phylogenetic analysis of complete genome and capsid protein sequences of JXGZ strain show that it was more closely related to GoAstV-1 strain than GoAstV-2 strain and was grouped within the GoAstV-1 cluster. These findings will aid in the development of efficient diagnostic reagents and possible vaccinations by providing insight into the prevalence and genetic evolution of GoAstV-1 in China.

Goose Nephritic Astrovirus Infection of Goslings Induces Lymphocyte Apoptosis, Reticular Fiber Destruction, and CD8 T-Cell Depletion in Spleen Tissue

The emergence of a novel goose nephritic astrovirus (GNAstV) has caused economic losses to the Chinese goose industry. High viral load is found in the spleen of goslings infected with GNAstV, but pathological injuries to the spleen due to GNAstV are largely unknown. In this study, 50 two-day-old goslings were infected orally with GNAstV, and 50 goslings were treated with PBS as control. Spleens were collected at different times following infection to assess damage. GNAstV infection caused visceral gout and urate deposition in joints, and resulted in 16% mortality. GNAstV was found in the lymphocytes and macrophages within the spleen. Lymphocyte loss, especially around the white pulp, and destruction and decline in the number of reticular fibers was observed in GNAstV-infected goslings. Moreover, in GNAstV-infected goslings, ultrahistopathological examination found that splenic lymphocytes exhibited condensed chromatin and apoptotic bodies, and reticular cells displayed damage to plasma membrane integrity and swollen mitochondria. Furthermore, TUNEL staining confirmed apoptosis of lymphocytes, and the mRNA levels of Fas and FasL were significantly increased in the GNAstV-infected goslings. In addition, GNAstV infection reduced the number and protein expression of CD8. In conclusion, GNAstV infection causes lymphocyte depletion, reticular cell necrosis, reticular fiber destruction, lymphocyte apoptosis, and reduction in CD8 levels, which contribute to spleen injury.