Isolation and characterization of a duck-origin goose astrovirus in China

The Development of a Sensitive Droplet Digital Polymerase Chain Reaction Test for Quantitative Detection of Goose Astrovirus

(1) Goose astrovirus (GAstV) is a novel emerging pathogen that causes significant economic losses in waterfowl farming. A convenient, sensitive, and specific detection method for GAstV in field samples is important in order to effectively control GAstV. Droplet digital polymerase chain reaction (ddPCR) is a novel, sensitive, good-precision, and absolute quantitation PCR technology which does not require calibration curves. (2) In this study, we developed a ddPCR system for the sensitive and accurate quantification of GAstV using the conserved region of the ORF2 gene. (3) The detection limit of ddPCR was 10 copies/µL, ~28 times greater sensitivity than quantitative real-time PCR (qPCR). The specificity of the test was determined by the failure of amplification of other avian viruses. Both ddPCR and qPCR tests showed good repeatability and linearity, and the established ddPCR method had high sensitivity and good specificity to GAstV. Clinical sample test results showed that the positive rate of ddPCR (88.89%) was higher than that of qPCR (58.33%). (4) As a result, our results suggest that the newly developed ddPCR method might offer improved analytical sensitivity and specificity in its GAstV measurements. The ddPCR could be widely applied in clinical tests for GAstV infections.

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.

Effects of Goose Astrovirus Type 2 Infection on Peripheral Blood Lymphocyte and Macrophage Activity In Vitro

Goose astrovirus type 2 (GAstV-2) is a novel pathogen causing visceral gout in goslings; it not only causes necrosis of renal epithelial cells but also causes spleen damage, indicating that GAstV-2 induces immunosuppression in goslings. However, to date, the interaction between GAstV-2 and immune cells remains unclear. In this study, peripheral blood lymphocytes and macrophages were isolated from goslings without GAstV-2 infection and then inoculated in vitro with GAstV-2, and the virus localization in the lymphocytes and macrophages, proliferation and apoptosis of lymphocytes, and phagocytic activity, reactive oxygen species (ROS) and nitric oxide (NO) production, and cell polarity in macrophages were determined. The results showed that GAstV-2 was observed in the cytoplasm of CD4 and CD8 T cells and macrophages, indicating that GAstV-2 can infect both lymphocytes and macrophages. GAstV-2 infection reduced the lymphocyte proliferation induced by Concanavalin A and lipopolysaccharide stimulation and increased the lymphocyte apoptosis rate and mRNA expression of Fas, demonstrating that GAstV-2 causes damage to lymphocytes. Moreover, GAstV-2 infection enhanced phagocytic activity and production of ROS and NO and induced a proinflammatory phenotype in macrophages (M1 macrophages), indicating that macrophages play an antiviral role during GAstV-2 infection. In conclusion, these results demonstrate that GAstV-2 infection causes damages to lymphocytes, and host macrophages inhibit GAstV-2 invasion during infection.

Isolation, Identification, and Pathogenicity of a Goose Astrovirus Genotype 1 Strain in Goslings in China

Goose astrovirus genotype 1 (GAstV-1) has emerged in goose farms in some provinces of China in recent years and is considered to be one of the pathogens of gout in goslings in China. However, few studies have been conducted on the dynamic distribution, tissue tropism, and pathogenesis of GAstV-1 in goslings. In 2022, an epidemiological investigation of goose astrovirus (GAstV) in goslings was conducted in seven provinces of China. During the investigation, a GAstV-1 designated as GAstV-JSXZ was identified in the kidney of an 8-day-old gosling and was successfully isolated from a goose embryo. The full genome sequence of GAstV-JSXZ was determined using the next-generation sequencing technique. The complete genome of GAstV-JSXZ was 7299-nt-long. Interestingly, the phylogenetic analysis revealed that Chinese GAstV-1 has formed two distinct subgroups based on the ORF 2 genomes, designated GAstV-1 1a and GAstV-1 1b. The GAstV-JSXZ shared the highest identity with GAstV-1 1a strain FLX and TZ03 in nucleotides (ORF1a: 98.3-98.4%; ORF1b: 92.3-99.1%; ORF2: 95.8-98.8%) and amino acid sequences (ORF1a: 99.4-99.5%; ORF1b: 98.2-98.8%; ORF2: 97.0-99.4%). To evaluate the pathogenicity of GAstV-1, 1-day-old goslings were inoculated with the virus by oral and subcutaneous injection routes, respectively. The results revealed that the virus causes extensive pathological organ damage, especially in the kidney, liver, and thymus. Virus-specific genomic RNA could be detected in the cloacal swabs and tissues of infected goslings throughout the experiment. The viral copy numbers examined in the kidney and intestine were the highest, followed by the liver and spleen. These results are likely to provide a new understanding of the pathogenicity of GAstV-1 in geese.

Epidemiological investigation and pathogenicity analysis of waterfowl astroviruses in some areas of China

Waterfowl astroviruses are mainly duck astroviruses and goose astroviruses, of which duck astroviruses (DAstV-3, -4), goose astroviruses (GoAstV-1, -2) are the four new waterfowl 21 astroviruses in recent years, which can lead to enteritis, viral hepatitis, gout and reduce the growth performance of waterfowl, affecting the healthy development of the waterfowl farming industry. Since no targeted drugs or vaccines on the market, studies on the epidemiology of the virus are necessary for vaccine development. In this study, we collected 1546 waterfowl samples from 13 provinces in China for epidemiological investigation. The results showed that 260 samples (16.8%) were positive. Four species of astrovirus were detected in 13 provinces except Fujian province. Among the four sites tested, the highest positive rates were found in farms and slaughterhouses. Cross-host and mixed infection were observed in four species of waterfowl astroviruses. The whole genome of 17 isolates was sequenced and compared with published sequences. Genetic evolution and homology analysis showed that the isolated strains had high similarity to their reference sequences. To assess the pathogenicity of GoAstV, 7-day-old goslings were inoculated with GoAstV-1 and GoAstV-2 by the intramuscular route, and infected geese showed similar clinical signs, such as anorexia, depression, and weight loss. Organ damage was seen after infection, with histopathological changes in the heart, liver, spleen, kidney, and intestine, and higher viral loads in throat and anal swabs. These findings increase our understanding of the pathogenicity of GoAstV-1 and GoAstV-2 in goslings and provide more references for future research.

Development and application of a multiplex PCR method for the simultaneous detection of goose parvovirus, waterfowl reovirus, and goose astrovirus in Muscovy ducks

A multiplex polymerase chain reaction (PCR) method was developed to detect and distinguish goose parvovirus (GPV), waterfowl reovirus (WRV), and goose astrovirus (GAstV). Three pairs of primers were designed based on conserved regions in the genomic sequences of these enteric viruses and were used to specifically amplify targeted fragments of 493 bp from the viral protein 3 (VP3) gene of GPV, 300 bp from the sigma A-encoding gene of WRV, and 156 bp from the capsid protein-encoding gene of GAstV. The results showed that the primers can specifically amplify target fragments, without any cross-amplification with other viruses, indicating that the method had good specificity. A sensitivity test showed that the detection limit of the multiplex PCR method was 1 × 103 viral copies. A total of 102 field samples from Muscovy ducks with clinically suspected diseases were evaluated using the newly developed multiplex PCR method. The ratio of positive samples to total samples for GPV, WRV, and GAstV was 73.53% (75/102) for multiplex PCR and was 73.53% (75/102) for routine PCR. Seventy-five positive samples were detected by both methods, for a coincidence ratio of 100%. This multiplex PCR method can simultaneously detect GPV, WRV, and GAstV, which are associated with viral enteritis, thereby providing a specific, sensitive, efficient, and accurate new tool for clinical diagnosis and laboratory epidemiological investigations.

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.

Base composition, adaptation, and evolution of goose astroviruses: codon-based investigation

Goose astroviruses (GoAstVs) are causative agents that account for fatal infection of goslings characterized by visceral urate deposition, resulting in severe economic losses in major goose-producing regions in China since 2017. In this study, we sought to unravel the intrinsic properties associated with adaptation and evolution in the host environment of GoAstVs. Consistent results from phylogenetic analysis and correspondence analysis performed on the codon usage patterns (CUPs) reveal 2 clusters of GoAstVs, namely, GoAstV-1 and GoAstV-2. However, multiple similar compositional characteristics were found, despite the high divergence between GoAstV-1 and GoAstV-2. Studies on the base composition of GoAstVs reveal an A/U bias, indicating a compositional constraint, while natural selection prevailed in determining the CUPs in the virus genome based on our neutrality plot analysis, reflecting high adaptive pressure to fit the host environment. Codon adaptation index (CAI) analysis revealed a higher degree of fitness to the CUPs of the corresponding host for GoAstVs than avian influenza virus and betacoronaviruses, which may be a favorable factor contributing to the high pathogenicity and wide distribution of GoAstVs in goslings. In addition, GoAstVs were less adapted to ducks and chickens, with significantly lower CAI values than to geese, which may be a reason for the different prevalence of GoAstVs among these species. Extensive investigations on dinucleotide distribution revealed a significant suppression of the CpG and UpA motifs in the virus genome, which may facilitate adaptation to the host's innate immune system by evading surveillance. In addition, our study reported the trends of increasing fitness to the host's microenvironment for GoAstVs through increasing adaptation to host CUPs and ongoing reduction of CpG motifs in the virus genome. The present analysis deepens our understanding of the basic biology, pathogenesis, adaptation and evolutionary pattern of GoAstVs, and contributes to the development of novel antiviral strategies.

Localization and distribution of goose astrovirus 2 antigens in different tissues at different times

Goose astrovirus 2 (GAstV-2) causes visceral gout in goslings and has resulted in significant economic losses in the goose industry of China since its outbreak in 2017. To further investigate the distribution and localization of GAstV-2 in different tissues at different times, a monoclonal antibody (mAb)-based immunohistochemical (IHC) assay was developed to detect GAstV-2. A total of 80 1-day-old healthy goslings were inoculated with GAstV-2 via the oral (n = 40) and intramuscular routes (n = 40). GAstV-2 in the tissues of interest was detected using the established IHC assay. The results showed that positive signals were detected in most tissues at 1 day post-infection (dpi). Viral antigens were mainly distributed in the cytoplasm, and the staining intensity was higher in the renal tubular epithelial cells than in other cells. Taken together, our data demonstrated that GAstV-2 has a broad tissue tropism and primarily targets the kidneys. These results are likely to provide a scientific basis for further elucidation of the pathogenesis of GAstV-2.

Isolation and genomic characterization of one novel goose astrovirus causing acute gosling gout in China

Novel goose astrovirus (NGAstV) is a member of the genus Avain Avastrovirus (AAstV) and the family Astroviridae. NGAstV-associated gout disease has caused huge economic losses to the goose industry worldwide. Since early 2020, NGAstV infections characterized by articular and visceral gout emerged continuously in China. Herein, we isolated a GAstV strain from goslings with fatal gout disease and sequenced its complete genome nucleotide sequence. Then we conducted systematic genetic diversity and evolutionary analysis. The results demonstrated that two genotypic species of GAstV (GAstV-I and GAstV-II) were circulating in China, and GAstV-II sub-genotype IId had become the dominant one. Multiple alignments of amino acid sequences of GAstV capsid protein revealed that several characteristic mutations (E456D, A464N, and L540Q) in GAstV-II d strains, as well as additional residues in the newly identified isolate which varied over time. These findings enrich the understanding of the genetic diversity and evolution of GAstV and may facilitate the development of effective preventive strategies.

Rapid diagnosis of duck Tembusu virus and goose astrovirus with TaqMan-based duplex real-time PCR

The mixed infection of duck Tembusu virus (DTMUV) and goose astrovirus (GoAstV) is an important problem that endangers the goose industry. Although quantitative PCR has been widely used in monitoring these two viruses, there is no reliable method to detect them at the same time. In this study, by analyzing the published genomes of DTMUV and goose astrovirus genotype 2 (GoAstV-2) isolated in China, we found that both viruses have high conservation, showing 96.5 to 99.5% identities within different strains of DTMUV and GoAstV, respectively. Subsequently, PCR primers and TaqMan probes were designed to identify DTMUV and GoAstV-2, and different fluorescent reporters were given to two probes for differential diagnosis. Through the optimization and verification, this study finally developed a duplex TaqMan qPCR method that can simultaneously detect the above two viruses. The lower limits of detection were 100 copies/μL and 10 copies/μL for DTMUV and GoAstV-2 under optimal condition. The assay was also highly specific in detecting one or two viruses in various combinations in specimens, and provide tool for clinical diagnosis of mixed infections of viruses in goose.

Detection and Characterization of Goose Astrovirus Infections in Hatcheries and Commercial Goose Flocks

Goose astrovirus (GoAstV) has frequently been isolated in China since it was first identified as the etiological agent of visceral gout in goslings in 2017. However, the actual prevalence of GoAstV infection and its economic impact on commercial goose production remain poorly characterized. Here, virus detection and serological testing were conducted to determine the extent of GoAstV infection in commercial goose flocks. We detected GoAstV RNA in 2% (6/300) of dead-in-shell embryos and day-old hatched goslings by RT-PCR, indicating vertical transmission under natural conditions. Using a virus neutralization test, GoAstV antibodies were detected in 41.7%–61.1% of serum samples from four commercial goose flocks, indicating that infections were common. To determine the virus types circulating in the commercial flocks, we isolated 15 GoAstVs from goose tissue samples from farms located in five provinces during 2018–2022. Genomic sequence analysis showed that all sequences were corresponded to GoAstV group 2 (GoAstV-2) but were assigned into three capsid subgroups based on sequence variations in the capsid protein. Representative isolates of capsid subgroups were also antigenically evaluated using cross-neutralization tests in LMH cell cultures. The antigenic relatedness values (R) calculated using the Horsfall formula were between 62% and 86%, indicating that no significant antigenic differences exist between the isolates. Our findings indicate that GoAstV-2 viruses are an important cause of fatal gout in goose flocks, as well as hatchery contamination in China.

Isolation, identification, and pathogenicity analysis of newly emerging gosling astrovirus in South China

Goose astroviruses (GoAstV) cause fatal gout and decrease product performance in the waterfowl industry across the world. Since no effective vaccines are available, studies on the epidemiology of the virus are necessary for vaccine development. In this study, we collected 94 gout samples from goose farms in the Guangdong Province of South China. Among them, 87 samples (92.6%) tested positive for GoAstV, out of which five GoAstV strains were isolated after four generations of blind transmission through healthy 13-day-old goose embryos. The whole genome of the isolates was sequenced and further analyzed by comparing the sequences with published sequences from China and other parts of the world. The results of the alignment analysis showed that nucleotide sequence similarities among the five GoAstV isolates were around 97.4-98.8%, 98.6-100%, 98.1-99.8%, and 96.7-100% for the whole genome, ORF1a, ORF1b, and ORF2, respectively. These results showed that the GoAstV isolates were highly similar to each other, although they were prevalent in five different regions of the Guangdong Province. The results of the phylogenetic analysis showed that the whole genome, along with the ORF1a, ORF1b, and ORF2 genes of the isolates, were clustered on a single branch, along with the recently published GoAstV-2, and were very distinct from the DNA sequences of the GoAstV-1 virus. In this study, we also reproduced the clinical symptoms of natural infection using the GoAstV-GD2101 isolates, confirming that the gout-causing pathogen in goslings was the goose astrovirus. These findings provided new insights into the pathogenicity and genetic evolution of GoAstV and laid the foundation for effectively controlling the disease.

Isolation and Pathogenicity of a Novel Goose Astrovirus from Overfed Adult Landaise Geese in China

Goose astrovirus (GAstV) is an important pathogen causing visceral gout and high mortality in goslings, which has broken out and spread across China. In 2021, a disease characterized by urate deposition on the visceral surface and 30% mortality occurred in commercial adult Landaise geese in Zhejiang Province, China. A systematic study identified an infecting astrovirus, designated ZJCX, that was efficiently isolated from a diseased goose with a chicken hepatocellular carcinoma cell line (LMH). In contrast to other GAstVs originating from goslings, ZJCX caused cytopathogenic effects in LMH cells, and the crystalline arrangement of viral particles was observed through transmission electron microscopy. Indeed, phylogenetic analysis and nucleotide homology comparison revealed that ZJCX isolate belongs to the genotype II cluster of GAstVs and displays 97.8-98.4% identity with other GAstV II strains. However, several specific mutations occurred in the polyprotein and capsid protein regions. Moreover, a pathogenicity assessment of ZJCX with a gosling model was conducted, and typical visceral gout was reproduced and led to 18% mortality. The viral loads of ZJCX in the blood, kidney, and liver were detected with specific primers after inoculation, which demonstrated that the kidney and liver presented viral loads peaking at seven days post-inoculation (dpi). Biochemical parameter examination showed that AST, ALT, γ-GT, UA, and BUN levels were significantly increased by GAstV, whereas body weight was reduced. Overall, this study indicated that the GAstV isolate could infect adult geese, and the results regarding the viral loads and biochemical parameters induced by ZJCX provide insight into GAstV pathogenicity.

An IgY Effectively Prevents Goslings from Virulent GAstV Infection

Goose astrovirus (GAstV) leads to viscera and joints urate deposition in 1- to 20-day-old goslings, with a mortality rate of up to 50%, posing a severe threat to entire colonies; however, there is no efficient prevention and control method for GAstV infection. This study describes a prophylactic anti-GAstV strategy based on the specific immunoglobulin Y (IgY) from egg yolk. The specific IgY was produced by 22-week-old laying hens intramuscularly immunized with the inactivated GAstV three consecutive times, with 2-week intervals. The egg yolk was collected weekly after the immunization and the anti-GAstV IgY titer was monitored using an agar gel immune diffusion assay (AGID). The results revealed that the AGID titer began to increase on day 7, reached a peak on day 49, and remained at a high level until day 77 after the first immunization. The specific IgY was prepared from the combinations of egg yolk from day 49 to day 77 through PEG-6000 precipitation. Animal experiments were conducted to evaluate the effects of prevention and treatment. The result of the minimum prophylactic dose of the IgY showed that the protection rate was 90.9% when 2.5 mg was administrated. Results of the prevention and the treatment experiments showed prevention and cure rates of over 80% when yolk antibody was administered in the early stages of the GAstV infection. These results suggested that the specific IgY obtained from immunized hens with the inactivated GAstV could be a novel strategy for preventing and treating GAstV infection.

Complete genome sequence and phylogenetic analysis of a goose astrovirus isolate in China

Astroviruses are considered the cause of gastroenteritis in humans and animals. Studies in recent years show avian astroviruses are also associated with duckling hepatitis, gosling gout, and chicken nephritis. In this study, a GAstV strain, designated as JS2019/China, was detected in dead goslings from a commercial goose farm in Jiangsu province of China. Viral strain was proliferated in goose embryos and sequence analysis showed the isolated strain had a classical structure arrangement and a series of conserved regions compared with other GAstVs. Sequence comparison and phylogenetic analysis of whole genome and ORF2 revealed that JS2019/China belongs to the GAstV-1 group, which consists of most of the GAstV strains. Amino acid analysis indicated that some mutants might have an impact on viral protease capacity, such as V505I and K736E of ORF1a and T107I, F342S, and S606P of ORF2. Taken together, a novel GAstV strain was isolated and genomic analysis and protein polymorphism analysis indicated that some amino acid mutants might affect the viral virulence.

Epidemiological investigation of infectious diseases in geese on mainland China during 2018-2021

Geese play an important role in agricultural economics, with China producing the vast majority of goose meat consumed worldwide annually. The variations in the avian viruses and co-infections result in substantial economic losses to the goose industry in China. To understand the evolutionary characteristics and co-infections of viruses, a broad epidemiological investigation of epizootic viruses of goose was carried out in nine provinces of China during 2018-2021. Here, the results indicated that, among the 1970 clinical samples, 50.81% (1001/1970) were positive for goose astrovirus (GAstV), 18.22% (359/1970) for avian orthoreovirus, 12.74% (251/1970) for goose parvovirus, 11.02% (217/1970) for H9N2 subtype avian influenza virus, 4.01% (79/1970) for Newcastle disease virus, and 2.08% (41/1970) for fowl adenovirus. Among the six viruses, co-infections comprised a large proportion (66.37%) in the field, of which the dual infection was more common. Additionally, phylogenetic analysis of GAstVs indicated that Chinese GAstVs had formed two distinct groups, that is, GAstV-1 and GAstV-2. GAstV-2 sub-genotype II-c had arisen as the dominant genotype in the whole country. Notably, all the H9N2-AIV isolated strains harboured the mammalian adaptation markers I155T, H183N, and Q226L (H3 numbering) in the HA gene, which promotes preferential binding to human-like α2-6-linked sialic acid receptors. And beyond that, we determined that the goose-origin Muscovy Duck Reovirus isolates, showing 51.7%-96% similarities to that of other waterfowl-origin orthoreovirus isolates in sequence homology analysis of the representative part of σC, are a new variant of waterfowl-origin orthoreovirus. These data provide valuable information about the prevalence of infectious diseases in geese on mainland China.

Facile, ultrasensitive, and highly specific diagnosis of goose astrovirus via reverse transcription-enzymatic recombinase amplification coupled with a CRISPR-Cas12a system detection

Fatal gout in geese caused by goose astrovirus (GAstV) has been spreading rapidly in China since 2018, causing serious economic losses in the goose breeding industry. To achieve simple, convenient and sensitive detection of GAstV, a novel diagnostic test was developed by combining reverse transcription-enzymatic recombinase amplification (RT-ERA) and CRISPR-Cas12a technologies. RT-ERA primers were designed to pre-amplify the conserved region of the ORF2 gene of GAstV and the predefined target sequence detected using the Cas12a/crRNA complex at 37℃ for 30 min. Specific detection of GAstV was achieved with no cross-reaction with non-GAstV templates and a sensitivity detection limit of 2 copies. The experimental procedure could be completed within 1 h, including RNA extraction (15 min), RT-ERA reaction (20 min), CRISPR-Cas12a/crRNA detection (5 min) and result readout (within 2 min) steps. In conclusion, the combination of RT-ETA and CRISPR-Cas12a provides a rapid and specific method that should be effective for the control and surveillance of GAstV infections in farms from remote locations.

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.

Genome Analysis of Goose-Origin Astroviruses Causing Fatal Gout in Shanghai, China Reveals One of Them Belonging to a Novel Type Is a Recombinant Strain

Since 2014, a goose-origin astroviruses disease, which is characterized by urate precipitation in viscera, has rapidly spread to major commercial goose provinces leading to huge economic losses in the poultry industry of China. In March 2020, a goose farm locates in Shanghai, China, where there was no goose astroviruses (GAstVs) infection reported before, experienced an outbreak of gout disease in geese. The etiological investigation was carried out by virus metagenomics and bacterial culture and two GAstVs strains, designated as CHSH01 and CHSH02, were determined. Their complete genomes were measured to 7,154 and 7,330 nt in length, excludingthe poly(A) tail, respectively, and had different genomic features and classifications. CHSH01 shared a very low sequence identity with other strains in terms of not only the complete genome but also different ORFs. Phylogenetic analysis showed CHSH02 belonged to GAstV-2, which was the predominant species in the geese with gout in China according to the previous study. Meanwhile, CHSH01 strain displayed low identity with other AstVs, and phylogenetic and recombination analysis suggested that CHSH01 belonging to a novel type was a recombinant strain, one parent strain of which was an AstV determined from a bar-headed goose (a kind of migrant bird). Moreover, the primary epidemiological investigation showed that the two strains were prevalent in the same goose farm and co-infection occurred. These findings arise the potential cross-species transmission of CHSH01 between domestic and wild fowl.

Insight into the Epidemiology and Evolutionary History of Novel Goose Astrovirus-Associated Gout in Goslings in Southern China

A novel gout disease, characterized by visceral urate deposition with high-mortality, with outbreaks in goslings in China since 2016 was caused by a novel goose astrovirus (GoAstV) and resulted in serious economic loss. However, the epidemiology and variation of the GoAstV in goslings in southern China and its evolutionary history as well as the classification of the GoAstV are unclear. In the present study, systematic molecular epidemiology, and phylogenetic analyses of the GoAstV were conducted to address these issues. Our results showed that the GoAstV is widespread in goslings in southern China, and the genomes of six GoAstV strains were obtained. Two amino acid mutations (Y36H and E456D) were identified in capsid proteins in this study, which is the dominant antigen for the GoAstV. In addition, the GoAstV could be divided into two distinct clades, GoAstV-1 and GoAstV-2, and GoAstV-2 is responsible for gout outbreaks in goslings and could be classified into Avastrovirus 3 (AAstV-3), while GoAstV-1 belongs to Avastrovirus 1 (AAstV-1). Moreover, the emergence of GoAstV-2 in geese was estimated to have occurred in January 2010, approximately 12 years ago, while GoAstV-1 emerged earlier than GoAstV-2 and was estimated to have emerged in April 1985 based on Bayesian analysis. The mean evolutionary rate for the GoAstV was also calculated to be approximately 1.42 × 10⁻³ nucleotide substitutions per site per year. In conclusion, this study provides insight into the epidemiology of the GoAstV in goslings in southern China and is helpful for understanding the origin and evolutionary history as well as the classification of the GoAstV in geese.

First Identification and Genetic Characterization of a Novel Duck Astrovirus in Ducklings in China

Four divergent groups of duck astroviruses (DAstVs) have been identified that infect domestic ducks. In March 2021, a fatal disease characterized by visceral urate deposition broke out in 5-day-old Beijing ducks on a commercial farm in Guangdong province, China. We identified a novel duck astrovirus from the ducklings suffering from gout disease. The complete genome sequence of this DAstV was obtained by virome sequencing and amplification. Phylogenetic analyses and pairwise comparisons demonstrated that this DAstV represented a novel group of avastrovirus. Thus, we designated this duck astrovirus as DAstV-5 JM strain. DAstV-5 JM shared genome sequence identities of 15–45% with other avastroviruses. Amino acid identities with proteins from other avastroviruses did not exceed 59% for ORF1a, 79% for ORF1b, and 60% for ORF2. The capsid region of JM shared genetic distances of 0.596 to 0.695 with the three official avastrovirus species. suggesting that JM could be classified as a novel genotype species in the Avastrovirus genus. Meanwhile, JM shares genetic distances of 0.402–0.662 with all the other known unassigned avastroviruses, revealing that it represents an additional unassigned avastrovirus. In summary, we determined that the DAstV-5 JM strain is a novel genotype species of avastrovirus.

Genetic diversity and evolution of goose astrovirus in the east of China

Goose astrovirus (GAstV), an agent of fatal visceral gout in goslings, has been widely circulating in eastern China since 2017, but little is known about its genetic diversity and systematic evolution. In this study, we isolated and sequenced nine nearly full-length GAstV genomes and conducted comprehensive genetic diversity and evolutionary analysis and compared them with other reported GAstV sequences. Our results indicated that two genotypic species of GAstV were circulating in China, and GAstV-2 subgenotype II-c had arisen as the dominant genotype in Shandong province and across the whole country. Multiple alignment of GAstV amino acid sequences revealed several characteristic mutations in GAstV-2 II-c strains, as well as additional residues in the nine new isolates which varied over time. Phylogenetic analysis of three open reading frames demonstrated different evolutionary histories. Evidence of natural recombination was also detected in GAstV, with most of the recombination occurring in the GAstV-2 II-c subgenotype. Molecular adaptation analyses revealed that the evolution of GAstV was shaped by strong negative selection, although a number of amino acids, which potentially affect host infection and cell entry, were subjected to positive pressure. Overall, these findings improve our understanding of the epidemiology and evolution of GAstV and may help in the development of vaccines and diagnostics. This article is protected by copyright. All rights reserved.

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.

The isolation and characterization of Duck astrovirus type- 1remerging in China

Since the first report from Cherry Valley ducks on a commercial duck farm in China (2008), duck astrovirus type 1(DAstV-1) -associated duck viral hepatitis (DVH) have been detected in several commercial duck flocks. A highly acute disease characterized by hepatitis broke out in ducklings in Shandong Province in March 2021, all diseased ducks have been immunized against duck viral hepatitis vaccine. One DAstV-1 strain, designated as DAstV-SDWF, was isolated from a diseased duckling. Here, the isolation, cultivation and characterization of DAstV-1 isolate are described. The isolated astrovirus grew well in the LMH cell line. To determine the entire genomic of the DAstV-SDWF isolate, next-generation sequencing (NGS) technique was conducted on Illumina HiSeq platform. Complete genome sequence analysis revealed that DAstV-SDWF isolate was 91.6%-98.6% homology with others DAstV-1 deposited in Genbank. Similar clinical symptoms were successful reproduced by experimental infection study using the DAstV-SDWF isolate. DAstV-SDWF is the first DAstV-1 strain whose experimental infection study has been conducted in China. Results of above data demonstrated the DAstV-1 could be one of the causative agents of the DVH occurring in China. The present works are likely to provide new insights into the pathogenicity and evolution of DAstV-1 in ducks. This article is protected by copyright. All rights reserved.

First report of a novel goose astrovirus outbreak in Muscovy ducklings in China

A highly acute disease characterized as visceral gout broke out in Muscovy ducklings in Henan province (China) in June 2020, with a mortality rate of up to 61%. In this study, common pathogenic agents were screened using reverse-transcription polymerase chain reaction or polymerase chain reaction. The results found the novel goose astrovirus (GoAstV) to be the pathogenic agent. We isolated the GoAstV, which has been designated as HNNY0620, using the Leghorn male chicken hepatocellular carcinoma (LMH) cell line and sequenced the complete genome. The phylogenetic tree showed that the amino acid (aa) sequences of ORF1a and ORF2 and the completed nucleotide sequences of the HNNY0620 strain were clustered in the GoAstV-I clade. ORF1a aa and whole-genome sequences were genetically close to TAstV-2 and DHV-3, whereas the ORF2 aa sequences were clustered with TAstV-2 and DHV2. Both the duck-origin GoAstVs and HNNY0620 harbored some special mutations, but ORF1a in 700 (I/T), ORF1b in 288 (F/L), and ORF2 in 306 (A/T) were only found in HNNY0620. These results suggest that the host range of GoAstV is diffusing, which can potentially affect other waterfowl.

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.

Isolation and evolutionary analyses of gout-associated goose astrovirus causing disease in experimentally infected chickens

Astroviruses are a common cause of gastroenteritis in humans and animals. They are also associated with extraintestinal infections, including hepatitis in ducklings, nephritis in chickens, as well as fatal meningitis and encephalitis in humans and other mammals. Since 2014, outbreaks of disease characterized by visceral gout and swelling of kidneys have been reported in goslings and ducklings in China, with the causative agent revealed to be a novel avian astrovirus designated goose astrovirus (GoAstV). In the present study, this novel gout-associated GoAstV was identified in diseased goslings from 2 farms in Hunan province, China. Three genomes were successfully sequenced and analyzed and were shown to have high identities of 99.7 to 99.8% between each other, with some specific amino acid alterations revealed in open reading frame 2 when compared with other gout-associated GoAstVs. Two strains were further efficiently isolated in the DF-1 chicken fibroblast cell line with high virus titers of 10¹¹ viral genomic copies per mL of culture media. A pilot virus challenge study using GoAstV in chickens demonstrated that this virus can cause clinical visceral gout in chickens, indicating its ability to cross the species barrier. Based on the phylogenetic analyses of capsid sequences, the identified GoAstVs were proposed to be classified into 2 genotypes, GoAstV1 and GoAstV2, and the novel gout-associated GoAstVs were all clustered in GoAstV2. Further Bayesian inference analyses indicated a nucleotide substitution rate of 1.46 × 10⁻³ substitutions/site/year for avian astrovirus based on open reading frame 2 sequences, and the time to the most recent common ancestor of GoAstVs was estimated to be around 2011. This is the first report to confirm GoAstV can infect chickens while also providing an estimation of the evolutionary rates of Avastroviruses.