The Broad Host Range and Genetic Diversity of Mammalian and Avian Astroviruses

Metatranscriptomic identification of novel RNA viruses from raccoon dog (Nyctereutes procyonoides) feces in Japan

The raccoon dog (Nyctereutes procyonoides), classified in the order Carnivora within the family Canidae, is native to East Asia and widely distributed throughout Japan due to its adaptability to various environments. Despite the close relationship between raccoon dogs and other animals, viruses infecting raccoon dogs have not been thoroughly investigated in Japan. In this study, we performed metatranscriptomic analyses using fecal samples collected from latrines of wild raccoon dogs in two locations on mainland Japan. Nearly complete viral genomes were identified, including viruses belonging to the genus Kobuvirus (CaKoV), an unclassified canine sapelovirus within the subfamily Ensavirinae (CaSaV), the Genius Mamastrovirus (CaAstV), unclassified hepe-astro-like virus (bastrovirus-like) (Bast-like V), and an unclassified dicistrovirus (DiciV) within the family Dicistroviridae. Phylogenetic analyses revealed that raccoon dog CaKoV, CaSaV, and CaAstV are related to canine strains but form independent clusters specific to raccoon dogs, suggesting they have evolved within this host population. Bast-like V, detected for the first time in raccoon dogs, showed high sequence identity with viruses previously identified in Chinese shrews. The shared insectivorous nature of these hosts and in silico host range predictions suggest that Bast-like Vs may originate from arthropod viruses. Although DiciV is likely of dietary origin due to its arthropod hosts, the large number of sequence reads detected and the phylogenetic clustering of raccoon dog DiciVs with mammalian DiciVs indicate the need to assess their potential infectivity in mammals and the risk of spillover. These findings suggest that raccoon dogs harbor endemic viruses within the canine population and may act as potential vectors for viruses with unknown infectivity in mammals but with spillover risk.

Global prevalence of Porcine Astrovirus: A systematic review and meta-analysis

Porcine astrovirus (PAstV) is a widespread enteric virus in pigs, often co-infecting with other enteric viruses and contributing to diarrhea, leading to significant economic losses in the global swine industry. This study aims to identify the factors influencing PAstV prevalence by conducting a statistical meta-analysis of global data and evaluating heterogeneity across various subgroups. A systematic literature search was performed across PubMed, Web of Science, CNKI, Wanfang, and VIP databases, covering studies from the inception of the databases up to December 2023. A random-effects model was employed to estimate the global pooled prevalence of PAstV infection, and subgroup analyses were performed to evaluate the impact of different continents, years, detection methods, and sample types on the prevalence. Publication bias was assessed using a funnel plot and Egger's test. A total of 45 studies from 10 countries across three continents, involving 376 articles, were included in the meta-analysis. The global pooled prevalence of PAstV infection was found to be 28.19 % (95 % CI, 21.94 %-34.89 %). Subgroup analysis indicated significant differences in PAstV prevalence across continents, with Asia at 26.25 % (95 % CI, 25.41 %-27.09 %), Europe at 36.19 % (95 % CI, 34.09 %-38.33 %), and North America at 63.24 %. The prevalence of PAstV was highest between 2012 and 2014 (49.86 %, 95 % CI, 47.21 %-52.51 %), followed by a decreasing trend that stabilized below 30 % from 2015 to 2023. The analysis showed no significant influence of detection methods on PAstV prevalence. However, the prevalence in non-fecal samples (43.09 %, 95 % CI: 41.05 %-45.15 %) was significantly higher than in fecal samples (22.92 %, 95 % CI: 21.87 %-23.99 %). Additionally, the prevalence of PAstV in asymptomatic pigs (36.71 %, 95 % CI, 34.97 %-38.48 %) exceeded that in diarrheic pigs (28.18 %, 95 % CI, 26.94 %-29.44 %). Among different age groups, nursery pigs(6-10 weeks) exhibited the highest infection rate (63.19 %, 95 % CI, 58.45 %-67.75 %), followed by weaning pigs(3-6 weeks) (60.00 %, 95 % CI, 56.48 %-63.45 %), finisher pigs(>10 weeks) (49.89 %, 95 % CI, 46.59 %-53.19 %), sows (35.33 %, 95 % CI, 31.45 %-39.37 %), with suckling pigs(0-3 weeks) showing the lowest rate (31.93 %, 95 % CI, 30.23 %-33.68 %). This study highlights the widespread nature of PAstV infection in pig populations globally, with notable variations in prevalence across regions, years, and sample types. The high prevalence of asymptomatic infections underscores the need for enhanced PAstV surveillance and control measures.

Mamastrovirus species are shaped by recombination and can be reliably distinguished in ORF1b genome region

Astroviruses are a diverse group of small non-enveloped positive sense single-stranded RNA viruses that infect animals and birds. More than half of all known genome sequences of mammalian astroviruses are not assigned to provisional species, and the biological mechanisms that could support segregation of astroviruses into species are not well understood. The systematic analysis of recombination in Mamastrovirus genomes available in GenBank was done to identify mechanisms providing genetic distinction between astroviruses. Recombination breakpoints were present in all Mamastrovirus genome regions, but occurred most commonly at the ORF1b/ORF2 junction. Recombination was ubiquitous within, but never between established and putative new species, and may be suggested as an additional species criterion. The current species criterion for the genus Mamastrovirus based on ORF2 amino acid sequence p-distances did not reliably distinguish several established species and was of limited use to identify distinct groups among unclassified astroviruses that were isolated recently, predominantly from cattle and pigs. A 17% nucleotide sequence distance cut-off in ORF1b fairly distinguished the established species and several groups among the unclassified viruses, providing better correspondence between phylogenetic grouping, reproductive isolation and the virus hosts. Sequence distance criteria (17% in nucleotide sequence of ORF1b and 25% in amino acid sequence of ORF2) and the recombination pattern corresponded fairly well as species criteria, but all had minor exclusions among mammalian astroviruses. A combination of these taxonomic criteria supported the established Mamastrovirus species and suggested redefining a few provisional species that were proposed earlier and introducing at least six novel species among recently submitted rat and bovine astroviruses.

Towards Detecting Associations of Canine Astrovirus and Caliciviruses with Health and Living Characteristics of Dogs in Greece

Astroviruses and caliciviruses are important causative agents of gastroenteritis in humans worldwide. They have been detected in a variety of animal species, including dogs, but their role in the induction of disease in animals remains uncertain. In a molecular study that was conducted in Greece, including healthy and gastroenteritis-affected dogs of different ages, astrovirus (AstV) and sapovirus (SaV) were detected in 15% and 26% of the examined animals, respectively. A specialized questionnaire was filled out for each of the dogs participating in the study, including information about different characteristics and risk factors that could possibly affect their health status. This information was analyzed with the use of two innovative statistical methods, i.e., a Multiple Correspondence Analysis (MCA) and the Ascending Hierarchical Classification (AHC). Based on their results, it was possible to define various groups of dogs based on their characteristics. AstV seems to occur more often in low-health-status dogs, usually mongrels, living in rural areas, showing vomit, diarrhea, and diet changes. Dogs of this group usually live with other pets in the same household and have frequent contact with stray animals. The presence of SaV does not seem to be associated with any of the examined factors.

Mamastrovirus spike protein: Sequence and structural characterization as a basis for understanding cross-species transmission

Astroviruses (AstVs) are notable for their propensity for cross-species transmission; however, the molecular determinants underlying this phenomenon remain poorly understood. The spike protein, which is responsible for host cell entry and is a major antigenic determinant, is hypothesized to play a pivotal role. In this study, we observed high sequence variability in the spike region of AstV. Structural analyses have revealed variability, arising from diverse evolutionary relationships, among AstVs of the same host origin. AstV spike proteins can be categorized into six groups, each of which encompasses AstVs from diverse hosts that exhibit high degrees of structural similarity. These six groups correspond to branches observed in the phylogenetic tree. Notably, the spike surface-exposed loops emerged as focal hotspots for B-cell epitopes across groups, with sequence variability that may contribute to immune evasion upon host switching. Differences in the spike structures of AstVs infecting the same host raise the possibility of distinct tissue tropisms and corresponding clinical manifestations. Collectively, our findings provide insights into the roles of spike protein similarities and immune epitope diversity in driving AstV cross-species transmission. Understanding these molecular mechanisms is crucial to predicting and mitigating the emergence of novel AstV strains.

Occurrence of astrovirus in young racing pigeons and genome characterization of 2 new astrovirus genomes representing 2 new species

Enteropathies are a serious concern in racing pigeons as they significantly impair performance in races and their training, and viruses are suspected to be one of the main factors. Astroviruses are well-known to be responsible for causing enteric disease in humans and various other animals including birds, although their prevalence and pathogenicity in pigeons is poorly understood. In this study, we investigated 2 groups of young racing pigeons (sick-study group and healthy-control group) to assess the correlation between the number of astrovirus genome copies in cloacal swabs and the occurrence of enteropathy. To determine this, we developed a novel TaqMan quantitative PCR (qPCR) and digital droplet PCR (ddPCR) methods for astrovirus detection and absolute quantitative analysis. We also performed high-throughput sequencing to obtain the complete genome sequences and establish the genetic similarity of the obtained strains to known astroviruses of poultry and other avian species. Two new complete genome sequences of pigeon astroviruses in the Avastrovirus genus were identified, representing 2 new species. These were found most closely related to astroviruses identified in Columbidae species and chickens. They share an average of 75.8% genome-wide pairwise identity and 57.6% and 64.6% capsid protein sequence identity with other unclassified columbid avastrovirus sequences in GenBank. Although the difference in prevalence of astrovirus in the study and control group was found statistically insignificant, there was a significant difference between the number of genome copies in positive samples from both groups. These unambiguous results leave the role of astroviruses as enteropathogenic factors in pigeons still undetermined.

Porcine Astrovirus Infection in Brains of Pigs in Korea

Recently, neurological diseases associated with astroviruses (AstVs) have been reported in pigs, ruminants, minks, and humans. In 2017, neuro-invasive porcine astrovirus (Ni-PAstV) 3 was detected in the central nervous system (CNS) of pigs with encephalomyelitis in Hungary and the USA. In the process of diagnosing domestic pigs exhibiting neurological signs, histopathologic lesions of non-suppurative encephalomyelitis with meningitis, neuronal vacuolation, and gliosis were detected, and PAstV was identified using reverse transcriptase PCR in CNS samples of four pigs in three farms from August to September in 2020, South Korea. Subsequently, the ORF2 region was successfully acquired from three brain samples, facilitating subsequent analysis. Four genotypes of PAstV (PAstV1, 3, 4, and 5) were detected, and coinfection of PAstV with multiple genotypes was observed in brain samples. This is the first study to report Ni-PAstV infection in pigs in South Korea.

First Report on Detection and Molecular Characterization of Astroviruses in Mongooses

Applying a pan-astrovirus (AstV) RT-hemi-nested PCR assay, we report here high detection rates (28.3%, 15/53) of AstVs in the small Indian mongoose (Urva auropunctata) on the Caribbean Island of St. Kitts. Based on deduced amino acid (aa) identities and phylogenetic analysis of long RNA-dependent RNA polymerase (RdRp) sequences (~315 aa, partial RdRp), the AstVs detected in the mongooses (designated as Mon-AstVs) were classified into two distinct groups (deduced aa identities of 66.45-67.30% between the groups). The putative RdRps of the Mon-AstVs shared low deduced aa identities with those of AstVs from other host species (<69%, <54%, and <50% identities with reptilian/amphibian AstVs, avastroviruses, and mamastroviruses, respectively). Phylogenetically, the group-I and group-II Mon-AstVs formed two distinct clusters, near the cluster of reptilian/amphibian AstVs, and were distantly related to avastroviruses and mamastroviruses. Since the mongooses were apparently healthy during sampling, we could not establish if the Mon-AstVs infected the animal or were of dietary origin. Although we could not ascertain the true host of the Mon-AstVs, phylogenetic analysis indicated that these viruses might have originated from lower vertebrates. To our knowledge, this is the first report on the detection and molecular characterization of AstVs in mongooses, highlighting the wide host range and significant genetic diversity within the family Astroviridae.

Next-generation sequencing technology reveals the viruses carried by poultry in the live poultry market of Guangdong, China

This study aimed to analyze the species and abundance of viruses carried by avian species in live poultry markets. In 2022, we collected 196 bird samples from two representative live poultry markets in Guangdong, China, of which 147 were randomly selected for metatranscriptome sequencing to construct a metatranscriptome library. This analysis yielded 17 viral families. Statistical analysis of the virus abundance of the six libraries showed that Picornaviridae, Retroviridae, Coronaviridae, and Othomyxoviridae were more abundant in the J1, J2, and J3 libraries, and Coronaviridae, Retroviridae, and Faviviridae were more abundant in the Y1, Y2, and E1 libraries. Finally, samples were screened using nested PCR and three viruses were identified. The positive results combined with high-throughput sequencing abundance data showed a positive correlation between virus abundance and the number of positive samples. This study provides scientific data to support the diagnosis and prevention of avian viral diseases.

Monitoring of Astroviruses, Brno-Hantaviruses, Coronaviruses, Influenza Viruses, Bornaviruses, Morbilliviruses, Lyssaviruses and Pestiviruses in Austrian Bats

Here, we report the results of a monitoring study of bat viruses in Austria to strengthen the knowledge of circulating viruses in Austrian bat populations. In this study, we analyzed 618 oropharyngeal and rectal swab samples from 309 bats and 155 pooled tissue samples from dead bats. Samples were collected from 18 different bat species from multiple locations in Austria, from November 2015 to April 2018, and examined for astroviruses, bornaviruses, coronaviruses, hantaviruses, morbilliviruses, orthomyxoviruses (influenza A/C/D viruses), pestiviruses and rhabdoviruses (lyssaviruses) using molecular techniques and sequencing. Using RT-qPCR, 36 samples revealed positive or suspicious results for astroviruses, Brno-hantaviruses, and coronaviruses in nine different bat species. Further sequencing revealed correspondent sequences in five samples. In contrast, none of the tested samples was positive for influenza viruses A/C/D, bornaviruses, morbilliviruses, lyssaviruses, or pestiviruses.

Identification and Full-Length Sequence Analysis of a Novel Recombinant Goat Astrovirus Genotype in Guangxi, China

Astroviruses are single-stranded, positive-sense RNA viruses capable of infecting humans as well as a wide range of mammalian and avian species, with a length of approximately 6.6-7.7 kb. In this study, 139 goat fecal samples collected from the Guangxi province were used for the RT-PCR detection, and two of these were positive for goat astrovirus, with a positivity rate of 1.44% (2/139). The complete genome sequence of an astrovirus strain and the partial genome sequence of a strain astrovirus, named GX WZ 2023 and GX HC 2023, were amplified and sequenced, and their sequence lengths were 6284 nt and 6213 nt, respectively. Among them, the capsid protein of goat astrovirus GX HC 2023 showed the highest amino acid identity of 95.9% with ovine astrovirus GX, which belonged to the MAstV-2 genotype. However, the closest relative of the GX WZ 2023 strain was found to be the caprine astrovirus Sichuan, with a nucleotide sequence identity of 76.8%. The ORF1ab nonstructural protein of this strain showed the highest amino acid identities of 89.2 and 95.8% with the ovine astrovirus S5.1 and caprine astrovirus G5.1 strains, respectively. However, its ORF2 capsid protein has 68.4% amino acid identity with the bovine astrovirus (BAstV) 16 2021 CHN strain and only 21.9-64% amino acid identity with all available strains of goat astrovirus. The GX WZ 2023 strain was recombined with the Chinese (BAstV 16 2021 CHN) and Japanese bovine strains (BAstV JPN 2015) in the ORF2 region. Therefore, the goat astrovirus GX WZ 2023 is proposed as a new member of the family goat astroviridae based on the species classification criteria of the International Committee on Taxonomy of Viruses. These findings enhance our understanding of the prevalence and genetic evolution of goat astrovirus and provide a scientific basis for future studies of these viruses in other animals.

Mouse and human immune responses share neutralization epitopes of HAstV-VA1

Astroviruses are highly divergent and infect a wide variety of animal hosts. In 2009, a genetically divergent human astrovirus (HAstV) strain VA1 was first identified in an outbreak of acute gastroenteritis. This strain has also been associated with fatal central nervous system disease. In this work, we report the isolation of three high-affinity neutralizing monoclonal antibodies (Nt-MAbs) targeting the capsid spike domain of HAstV-VA1. These antibodies (7C8, 2A2, 3D8) were used to select individual HAstV-VA1 mutants resistant to their neutralizing activity and a HAstV-VA1 triple mutant that escapes neutralization from all three Nt-MAbs. Sequencing of the virus genome capsid region revealed escape mutations that map to the surface of the capsid spike domain, define three potentially independent neutralization epitopes, and help delineate four antigenic sites in human astroviruses. Notably, two of the escape mutations were found to be present in the spike sequence of the HAstV-VA1-PS strain isolated from an immunodeficient patient with encephalitis, suggesting that those mutations arose as a result of the immune pressure generated by the patient's immunotherapy. In agreement with this observation, human serum samples exhibiting strong neutralization activity against wild-type HAstV-VA1 had a 2.6-fold reduction in neutralization titer when evaluated against the triple-escape HAstV-VA1 mutant, suggesting that both mouse and human antibody responses target shared neutralization epitopes. The isolated Nt-MAbs reported in this work will help to characterize the functional domains of the virus during cell entry and have the potential for developing a specific antibody therapy for the neurological disease associated with HAstV-VA1.

IMPORTANCE

Human astroviruses (HAstVs) have been historically associated with acute gastroenteritis. However, the genetically divergent HAstV-VA1 strain has been associated with central nervous system disease. In this work high-affinity neutralizing monoclonal antibodies directed to HAstV-VA1 were isolated and characterized. The proposed binding sites for these antibodies and for neutralizing antibodies against classical HAstVs suggest that there are at least four neutralization sites on the capsid spike of astroviruses. Our data show that natural infection with human astrovirus VA1 elicits a robust humoral immune response that targets the same antigenic sites recognized by the mouse monoclonal antibodies and strongly suggests the emergence of a variant HAstV-VA1 virus in an immunodeficient patient with prolonged astrovirus infection. The isolated Nt-MAb reported in this work will help to define the functional sites of the virus involved in cell entry and hold promise for developing a specific antibody therapy for the neurological disease associated with HAstV-VA1.

Establishment and application of quadruple fluorescence quantitative RT-PCR method for the identification of waterfowl astrovirus

Avian astrovirus can infect a variety of poultry species and cause viral diarrhea, with a wide epidemic range strong pathogenicity and a high incidence. Among them, Duck astrovirus 3(DAstV-3), Duck astrovirus 4(DAstV-4), Goose astrovirus 1(GoAstV-1) and Goose astrovirus 2(GoAstV-2) are four types of astroviruses newly discovered in waterfowl in recent years. In order to realize the rapid detection of these four kinds of waterfowl stellate viruses, specific primers and probes were engineered to target a highly conserved region of ORF1b gene of DAstV-3, GoAstV-1 and GoAstV-2 and the ORF2 gene of DAstV-4, and a quadruple fluorescence quantitative RT-PCR method was developed. The results indicate that the method established in this study has good specificity and no cross reactivity with other pathogens. This method can detect viruses with a minimum concentration of 1 × 101 copies/μL for DAstV-4, GoAstV-1 and GoAstV-2, respectively, while the minimum concentration for DAstV-3 is 1 × 102 copies/μL. Compared with the routinely used RT-PCR method, the limit of detection by the multiplex RT-PCR lower. Both intra- and inter-assay variability tests revealed excellent reproducibility. This method was then used to analyze 269 field samples, and the results were verified by genome sequencing. In conclusion, this study presents a sensitive, accurate, and specific method for detecting DAstV-3, DAstV-4, GoAstV-1, and GoAstV-2 in a single reaction, enabling the monitoring and differential diagnosis of these four types of waterfowl astroviruses.

Genetic diversity of astroviruses detected in wild aquatic birds in Hong Kong

Wild waterfowl serve as a reservoir of some astroviruses. Fecal samples from wild waterfowl collected at Hong Kong's Marshes were tested using pan-astrovirus reverse transcription-PCR. Positive samples underwent subsequent host identification using DNA barcoding. Based on deduced partial sequences, noteworthy samples from three astrovirus groups (mammalian, avian and unclassified astroviruses) were further analyzed by next-generation sequencing. One sample of Avastrovirus 4 clade, MP22-196, had a nearly complete genome identified. The results of ORF2 phylogenetic analysis and genetic distance analysis indicate that Avastrovirus 4 is classified as a distinct subclade within Avastrovirus. MP22-196 has typical astrovirus genome characteristics. The unique characteristics and potential differences of this genome, compared to other avian astrovirus sequences, involve the identification of a modified sgRNA sequence situated near the ORF2 start codon, which precedes the ORF1b stop codon. Additionally, the 3' UTR of MP22-196 is shorter than other avian astroviruses. This study expands our understanding of the Avastrovirus 4 clade.

Development of a label-free photoelectrochemical immunosensor for novel astrovirus detection

Since 2017, an infectious goose gout disease characterized by urate precipitation in viscera, mainly caused by novel goose astrovirus (GoAstV) infection, has emerged in the main goose-producing region of China. The current challenge in managing goose gout disease is largely due to the absence of a rapid and efficient detection method for the GoAstV pathogen. Notably, the potential application of immunosensors in detecting GoAstV has not yet been explored. Herein, a label-free PEC immunosensor was fabricated by using purchased TiO2 as the photoactive material and antibody against GoAstV P2 proteins as the specific recognition element. First, we successfully expressed the capsid spike domain P2 protein of ORF2 from GoAstV CHSH01 by using the pET prokaryotic expression system. Meanwhile, the polyclonal antibody against GoAstV capsid P2 protein was produced by purified protein. To our knowledge, this is the first establishment and preliminary application of the label-free photoelectrochemical immunosensor method in the detection of AstV. The PEC immunosensor had a linear range of 1.83 fg mL-1 to 3.02 ng mL-1, and the limit of detection (LOD) was as low as 0.61 fg mL-1. This immunosensor exhibited high sensitivity, great specificity, and good stability in detecting GoAstV P2 proteins. To evaluate the practical application of the immunosensor in real-world sample detection, allantoic fluid from goose embryos was collected as test samples. The results indicated that of the eight positive samples, one false negative result was detected, while both negative samples were accurately detected, suggesting that the constructed PEC immunosensor had good applicability and practical application value, providing a platform for the qualitative detection of GoAstV.

Epidemiological Investigation of Goose Astrovirus in Hebei Province, China, 2019-2021

The goose astrovirus (GAstV), a key pathogen causing visceral gout and high mortality in geese, has spread widely in China, with frequent outbreaks in recent years. Outbreaks and transmissions of this virus have been reported across China, causing considerable economic losses to the goose industry worldwide, with losses exceeding tens of billions in China alone. However, there is still no effective prevention strategy against this virus. Therefore, continuous monitoring of the genetic diversity of dominant GAstV strains is crucial for developing targeted vaccines and appropriate therapeutics. As a crucial region for goose breeding in China, Hebei Province has previously lacked reports on the epidemiology of GAstV. Hence, investigating the epidemiology of GAstV in Hebei Province is highly important. From January 2019 to December 2021, 474 samples suspected of having a GAstV infection were collected in Hebei Province in this study. Through detailed histological observations, pathological examinations, virus isolation and identification, and genetic diversity analysis, we found that GAstV-2 has become the predominant circulating genotype. However, the presence of GAstV-1 and mixed infections cannot be ignored and should receive increased attention. The findings of this study not only deepened our understanding of GAstV in waterfowl in China but also provided scientific evidence for developing effective prevention and control measures, thereby promoting the healthy development of the goose industry in China.

Characterization of natural co-infection with goose astrovirus genotypes I and II in gout affected goslings

RESEARCH HIGHLIGHTS

Urate tophi were found in the kidneys, liver, spleen and lungs.IFA confirmed the co-expression of GoAstV-I and II antigens in the same kidney.

First Detection of Benign Rabbit Caliciviruses in Chile

Pathogenic lagoviruses (Rabbit hemorrhagic disease virus, RHDV) are widely spread across the world and are used in Australia and New Zealand to control populations of feral European rabbits. The spread of the non-pathogenic lagoviruses, e.g., rabbit calicivirus (RCV), is less well studied as the infection results in no clinical signs. Nonetheless, RCV has important implications for the spread of RHDV and rabbit biocontrol as it can provide varying levels of cross-protection against fatal infection with pathogenic lagoviruses. In Chile, where European rabbits are also an introduced species, myxoma virus was used for localised biocontrol of rabbits in the 1950s. To date, there have been no studies investigating the presence of lagoviruses in the Chilean feral rabbit population. In this study, liver and duodenum rabbit samples from central Chile were tested for the presence of lagoviruses and positive samples were subject to whole RNA sequencing and subsequent data analysis. Phylogenetic analysis revealed a novel RCV variant in duodenal samples that likely originated from European RCVs. Sequencing analysis also detected the presence of a rabbit astrovirus in one of the lagovirus-positive samples.

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.

Antigenic determinants of HAstV-VA1 neutralization and their relevance in the human immune response

Astroviruses are highly divergent and infect a wide variety of animal hosts. In 2009, a genetically divergent human astrovirus (HAstV) strain VA1 was first identified in an outbreak of acute gastroenteritis. This strain has also been associated with fatal central nervous system disease. In this work, we report the isolation of three high-affinity neutralizing monoclonal antibodies (Nt-MAbs) targeting the capsid spike domain of HAstV-VA1. These antibodies (7C8, 2A2, 3D8) were used to select individual HAstV-VA1 mutants resistant to their neutralizing activity and also select a HAstV-VA1 triple mutant that escapes neutralization from all three Nt-MAbs. Sequencing of the virus genome capsid region revealed escape mutations that map to the surface of the capsid spike domain, define three potentially independent neutralization epitopes, and help delineate four antigenic sites in rotaviruses. Notably, two of the escape mutations were found to be present in the spike sequence of the HAstV-VA1-PS strain isolated from an immunodeficient patient with encephalitis, suggesting that those mutations arose as a result of the immune pressure generated by the patient's immunotherapy. In accordance with this observation, human serum samples exhibiting strong neutralization activity against wild-type HAstV-VA1 had a 2.6-fold reduction in neutralization titer when evaluated against the triple-escape HAstV-VA1 mutant, indicating shared neutralization epitopes between the mouse and human antibody response. The isolated Nt-MAbs reported in this work will help characterize the functional sites of the virus during cell entry and have the potential for developing a specific antibody therapy for the neurological disease associated with HAstV-VA1.

Importance

Human astroviruses (HAstVs) have been historically associated with acute gastroenteritis. However, the genetically divergent HAstV-VA1 strain has been associated with central nervous system disease. This work isolated high-affinity neutralizing monoclonal antibodies directed to HAstV-VA1. The proposed binding sites for these antibodies, together with previously reported sites for neutralizing antibodies against classical HAstVs, suggest the existence of at least four neutralization sites on the capsid spike of astroviruses. Our data show that natural infection with human astrovirus VA1 elicits a robust humoral immune response that targets the same antigenic sites recognized by the mouse monoclonal antibodies and strongly suggests the emergence of a variant HAstV-VA1 virus in an immunodeficient patient with prolonged astrovirus infection. The isolated Nt-MAb reported in this work will be helpful in defining the functional sites of the virus involved in cell entry and hold promise for developing a specific antibody therapy for the neurological disease associated with HAstV-VA1.

Diversity of astroviruses in wild animals in Yunnan province, China

BACKGROUND

Astroviruses (AstVs) are single-stranded RNA viruses that have been detected in a wide range of mammals and birds. They are associated with numerous interspecies transmissions and viral recombination events, posing a threat to human and animal health.

METHODS

We collected 1,333 samples from wild animals, including bats, rodents, wild boars, and birds, from various states and cities in the Yunnan Province, China, between 2020 and 2023 to investigate the presence of AstVs. AstVs were detected using a polymerase chain reaction targeting the RdRp gene. Finally, the Molecular Evolutionary Genetics Analysis software was used to construct the phylogenetic tree.

RESULTS

The overall positivity rate for AstVs was 7.12% in four species, indicating their widespread occurrence in the region. High genetic diversity among AstVs was observed in different animal species, suggesting the potential for interspecies transmission, particularly among rodents and birds. Additionally, we identified a novel AstV strain and, for the first time, provided information on the presence of bastroviruses in Yunnan, China.

CONCLUSIONS

The widespread distribution and high genetic diversity of AstVs, along with the observed potential for interspecies transmission, highlight the importance of further investigation and surveillance in the region. The findings emphasize the need for increased attention to AstVs and their potential impact on human and animal health in Yunnan and other regions.

A survey of fecal virome and bacterial community of the diarrhea-affected cattle in northeast China reveals novel disease-associated ecological risk factors

Limited information on the virome and bacterial community hampers our ability to discern systemic ecological risk factors that cause cattle diarrhea, which has become a pressing issue in the control of disease. A total of 110 viruses, 1,011 bacterial genera, and 322 complete viral genomes were identified from 70 sequencing samples mixed with 1,120 fecal samples from 58 farms in northeast China. For the diarrheic samples, the identified virome and bacterial community varied in terms of composition, abundance, diversity, and geographic distribution in relation to different disease-associated ecological factors; the abundance of identified viruses and bacteria was significantly correlated with the host factors of clinical status, cattle type, and age, and with environmental factors such as aquaculture model and geographical location (P < 0.05); a significant interaction occurred between viruses and viruses, bacteria and bacteria, as well as between bacteria and viruses (P < 0.05). The abundance of SMB53, Butyrivibrio, Facklamia, Trichococcus, and Turicibacter was significantly correlated with the health status of cattle (P < 0.05). The proportion of BRV, BCoV, BKV, BToV, BoNoV, BoNeV, BoAstV, BEV, BoPV, and BVDV in 1,120 fecal samples varied from 1.61% to 12.05%. A series of significant correlations were observed between the prevalence of individual viruses and the disease-associated ecological factors. A genome-based phylogenetic analysis revealed high variability of 10 bovine enteric viruses. The bovine hungarovirus was initially identified in both dairy and beef cattle in China. This study elucidates the fecal virome and bacterial community signatures of cattle affected by diarrhea, and reveals novel disease-associated ecological risk factors, including cattle type, cattle age, aquaculture model, and geographical location.IMPORTANCEThe lack of data on the virome and bacterial community restricts our capability to recognize ecological risk factors for bovine diarrhea disease, thereby hindering our overall comprehension of the disease's cause. In this study, we found that, for the diarrheal samples, the identified virome and bacterial community varied in terms of composition, abundance, diversity, configuration, and geographic distribution in relation to different disease-associated ecological factors. A series of significant correlations were observed between the prevalence of individual viruses and the disease-associated ecological factors. Our study aims to uncover novel ecological risk factors of bovine diarrheal disease by examining the pathogenic microorganism-host-environment disease ecology, thereby providing a new perspective on the control of bovine diarrheal diseases.

Leveraging machine learning for taxonomic classification of emerging astroviruses

Astroviruses are a family of genetically diverse viruses associated with disease in humans and birds with significant health effects and economic burdens. Astrovirus taxonomic classification includes two genera, Avastrovirus and Mamastrovirus. However, with next-generation sequencing, broader interspecies transmission has been observed necessitating a reexamination of the current host-based taxonomic classification approach. In this study, a novel taxonomic classification method is presented for emergent and as yet unclassified astroviruses, based on whole genome sequence k-mer composition in addition to host information. An optional component responsible for identifying recombinant sequences was added to the method's pipeline, to counteract the impact of genetic recombination on viral classification. The proposed three-pronged classification method consists of a supervised machine learning method, an unsupervised machine learning method, and the consideration of host species. Using this three-pronged approach, we propose genus labels for 191 as yet unclassified astrovirus genomes. Genus labels are also suggested for an additional eight as yet unclassified astrovirus genomes for which incompatibility was observed with the host species, suggesting cross-species infection. Lastly, our machine learning-based approach augmented by a principal component analysis (PCA) analysis provides evidence supporting the hypothesis of the existence of human astrovirus (HAstV) subgenus of the genus Mamastrovirus, and a goose astrovirus (GoAstV) subgenus of the genus Avastrovirus. Overall, this multipronged machine learning approach provides a fast, reliable, and scalable prediction method of taxonomic labels, able to keep pace with emerging viruses and the exponential increase in the output of modern genome sequencing technologies.

Prevalence of Astroviruses in Different Animal Species in Poland

Astroviruses (AstVs) are small RNA viruses characterized by a high mutation rate, the ability to recombine, and interspecies transmission, which allows them to infect a multitude of hosts including humans, companion animals, and farmed animals as well as wildlife. AstVs are stable in the environment, and their transmission is usually through the fecal-oral route or via contaminated water and food. Although direct zoonotic transmission was not confirmed, interspecies transmission events have occurred or have been indicated to occur in the past between wild and domestic animals and humans. They cause large economic losses, mainly in the poultry sector, due to gastroenteritis and mortality. In young children, they are the second most common cause of diarrhea. This study involved 166 intestine samples and pools of spleen, lymph node, and kidney samples collected from 352 wild animals, 52 pigs, and 31 companion animals. Astroviruses were detected in the intestine samples and were separately detected in pools of tissue samples prepared for individual animals using a heminested RT-PCR protocol. Amplicons were subjected to Sanger sequencing, and a phylogenetic analysis of 320 nt RNA-dependent RNA polymerase (RdRp) fragments referring to known nt sequences of astroviruses was performed. Astroviral RNA was detected in the intestine samples and/or tissue pools of red foxes (nine positive intestines and six positive tissue pools), rats (two positive intestines and three positive tissue pools), a cat (one AstV detected in an intestine sample), pigs (eight positive tissue pools), and wild boars (two positive pools of spleens, kidneys, and lymph nodes). No astroviral RNA was detected in wild mustelids, dogs, or other small wild animals including rodents. A phylogenetic analysis revealed that the astroviruses detected during this study were mostly host-specific, such as porcine, canine, and rat astroviruses that were highly homologous to the sequences of reference strains. In one of two wild boars, an AstV distinct to porcine species was found with the highest nt identity to Avastroviruses, i.e., turkey astroviruses, which suggests potential cross-species transmission of the virus, as previously described. Here, we present the first detection of astroviruses in the population of wild animals, companion animals, and pigs in Poland, confirming that astroviruses are frequent pathogens circulating in animals in the field. Our study also suggests potential cross-species transmission of Avaastrovirus to wild boars; however, further molecular characterization is needed.

The genomic and epidemiological investigations of enteric viruses of domestic caprine (Capra hircus) revealed the presence of multiple novel viruses related to known strains of humans and ruminant livestock species

IMPORTANCE

Compared with other domestic animals, the virome and viral diversity of small ruminants especially in caprine are less studied even of its zoonotic potential. In this study, the enteric virome of caprine was investigated in detail using next-generation sequencing and reverse transcription PCR techniques. The complete or nearly complete genomes of seven novel viruses were determined which show a close phylogenetic relationship to known human and ruminant viruses. The high similarity between the identified caprine tusavirus (family Parvoviridae) and an unassigned CRESS DNA virus with closely related human strains could indicate the (reverse) zoonotic potential of these viruses. Others, like astroviruses (family Astroviridae), enteroviruses, or novel caripiviruses (named after the term caprine picornavirus) of family Picornaviridae found mostly in multiple co-infections in caprine and ovine, could indicate the cross-species transmission capabilities of these viruses between small ruminants.

Molecular characteristics and pathogenicity of a novel chicken astrovirus variant

It is well-established that the genetic diversity, regional prevalence, and broad host range of astroviruses significantly impact the poultry industry. In July 2022, a small-scale commercial broiler farm in China reported cases of growth retardation and a 3% mortality rate. From chickens displaying proventriculitis and pancreatitis, three chicken astroviruses (CAstV) isolates were obtained and named SDAU2022-1-3. Complete genomic sequencing and analysis revealed the unique characteristics of these isolates from known CAstV strains in ORF1a, ORF1b, and ORF2 genes, characterized by an unusually high variability. Analysis of amino acid mutations in ORF1a, ORF1b, and ORF2 indicated that the accumulation of these mutations played a pivotal role in the emergence of the variant strain. Inoculation experiments demonstrated that affected chickens exhibited liver and kidney enlargement, localized proventricular hemorrhage, and a dark reddish-brown appearance in about two-thirds of the pancreas. Histopathological examination unveiled hepatic lymphocytic infiltration, renal tubular epithelial cell swelling, along with lymphocytic proventriculitis and pancreatitis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis indicated viremia and viral shedding at 3 days post-infection (dpi). The proventriculus displayed the highest viral loads, followed by the liver, kidney, duodenum, and pancreas. Liver parameters (AST and ALT) and kidney parameters (UA and UN) demonstrated mild damage consistent with earlier findings. While the possibility of new mutations in the ORF2 gene of CAstV causing proventriculitis and pancreatitis warrants further investigation, these findings deepen our comprehension of CAstV's pathogenicity in chickens. Additionally, they serve as valuable references for subsequent research endeavors.

Universal primer multiplex PCR assay for detection and genotyping of porcine astroviruses

Porcine astroviruses (PAstV) are members of the family Astroviridae, Mamastravirus genus and have been identified to have five genotypes (PAstV1-5). These viruses are highly prevalent in pigs and can cause enteric disease as well as neurological or respiratory symptoms depending on their genotypes. At present, the epidemiological impacts of some PAstV genotypes on pigs are largely unknown and hence continuously monitoring of these PAstVs may be needed. The purpose of this research was to develop an improved and efficient detection tool for PAstVs and to evaluate the developed method using clinical samples. Initially, a set of five chimeric primers (CP), each comprising genotype specific primer pairs with an identical universal adapter at the 5' end, and a universal primer (UP) that is identical to universal adapter sequence, were designed. With these tools in place, a novel multiplex PCR system with universal primer was established for the simultaneous detection of the five types of PAstV. This method can specifically detect PAstV genotypes, with a limit of detection (LOD) of 5 copies/μL for each genotype irrespective of single or mixed target template. Using this new assay, 273 pig fecal samples were investigated for further assay evaluation. Among all samples, the positive rate was 70.0% with PAstV4 in 56.8% of the samples, PAstV2 in 38.8%, PAstV1 in 16.8%, and PAstV5 in 11.0%. More than one PAstV in a sample were detected in 39.2% of the samples. The consistency rate between the novel multiplex PCR and singleplex PCRs was 96.4-100%. Given its rapidity, specificity and sensitivity, the novel multiplex PCR is a useful approach for demonstrating single or mixed genotype infections of PAstV.

Evaluating the zoonotic potential of RNA viromes of rodents provides new insight into rodent-borne zoonotic pathogens in Guangdong, China

Emerging and re-emerging infectious diseases have been on the rise, with a significant proportion being zoonotic. Rodents, as the natural reservoirs of numerous diverse zoonotic viruses, pose a substantial threat to human health. To investigate the diversity of known and unknown viruses harbored by rodents in Guangdong (southern province of China), we conducted a comprehensive analysis of viral genomes through metagenomic sequencing of organs from 194 rodents. Our analysis yielded 2163 viral contigs that were assigned to 25 families known to infect a wide range of hosts, including vertebrates, invertebrates, amoebas, and plants. The viral compositions vary considerably among different organs, but not in rodent species. We also assessed and prioritized zoonotic potential of those detected viruses. Ninety-two viral species that are either known to infect vertebrates and invertebrates or only vertebrates were identified, among which 21 are considered high-risk to humans. The high-risk viruses included members of the Hantavirus, Picobirnaviruses, Astroviruses and Pestivirus. The phylogenetic trees of four zoonotic viruses revealed features of novel viral genomes that seem to fit evolutionarily into a zone of viruses that potentially pose a risk of transmission to humans. Recognizing that zoonotic diseases are a One Health issue, we approached the problem of identifying the zoonotic risk from rodent-transmitted disease in the Guangdong province by performing next-generation sequencing to look for potentially zoonotic viruses in these animals.

Rapid detection of goose astrovirus genotypes 2 using real-time reverse transcription recombinase polymerase amplification

BACKGROUND

Goose astrovirus (GoAstV) is an important pathogen that causes joint and visceral gout in goslings. It has been circulating in many provinces of China since 2017. Goose astrovirus genotypes 2 (GoAstV-2) is the main epidemic strain, and its high morbidity and mortality have caused huge economic losses to the goose industry. An accurate point-of-care detection for GoAstV-2 is of great significance. In this study, we developed a real-time reverse transcription recombinase polymerase amplification (RT-RPA) method for the on-site detection of GoAstV-2 infection.

RESULTS

The real-time RT-RPA reaction was carried out at a constant temperature of 39 °C, and the entire detection time from nucleic acid preparation to the end of amplification was only 25 min using the portable device. The results of a specificity analysis showed that no cross-reaction was observed with other related pathogens. The detection limit of the assay was 100 RNA copies/μL. The low coefficient of variation value indicated excellent repeatability. We used 270 clinical samples to evaluate the performance of our established method, the positive concordance rates with RT-qPCR were 99.6%, and the linear regression analysis revealed a strong correlation.

CONCLUSIONS

The established real-time RT-RPA assay showed high rapidity, specificity and sensitivity, which can be widely applied in the laboratory, field and especially in the resource-limited settings for GoAstV-2 point-of-care diagnosis.

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.

Virome of high-altitude canine digestive tract and genetic characterization of novel viruses potentially threatening human health

The majority of currently emerging infectious illnesses are zoonotic infections, which have caused serious public health and economic implications. The development of viral metagenomics has helped us to explore unknown viruses. We collected 1,970 canine feces from Yushu and Guoluo in the plateau region of China for this study to do a metagenomics analysis of the viral community of the canine digestive tract. Our analysis identified 203 novel viruses, classified into 11 known families and 2 unclassified groups. These viruses include the hepatitis E virus, first identified in dogs, and the astrovirus, coronavirus, polyomavirus, and others. The relationship between the newly identified canine viruses and known viruses was investigated through the use of phylogenetic analysis. Furthermore, we demonstrated the cross-species transmission of viruses and predicted new viruses that may cause diseases in both humans and animals, providing technical support for the prevention and control of diseases caused by environmental pollution viruses. IMPORTANCE Most emerging infectious diseases are due to zoonotic disease agents. Because of their effects on the security of human or animal life, agriculture production, and food safety, zoonotic illnesses and livestock diseases are of worldwide significance. Because dogs are closely related to humans and domestic animals, they serve as one of the important links in the transmission of zoonotic and livestock diseases. Canines can contaminate the environment in which humans live such as water and soil through secretions, potentially altering the human gut microbiota or causing diseases. Our study enriched the viral community in the digestive tract microbiome of dogs and found types of viruses that threaten human health, providing technical support for the prevention and control of early warning of diseases caused by environmental contaminant viruses.

Identification of new astroviruses in synanthropic squamates

Astroviruses have been identified in a wide variety of animal species and are associated with gastro-intestinal disease in humans. Pathologies due to extra-intestinal localization are known in different hosts. We report the detection of astroviruses in synanthropic squamate reptile species (Podercis siculus and Tarentola mauritanica). Fecal samples were collected from 100 squamates from urban and peri-urban areas of three regions in South Italy and tested for the presence of astroviruses using a broadly reactive (pan-astrovirus) RT-PCR protocol targeting the RNA-dependent RNA polymerase. Astrovirus RNA was detected in 11% of the samples and for six strains a 3 kb-long fragment at the 3' end of the genome was sequenced, obtaining information on the complete capsid-encoding ORF2 sequence. Viral RNA was also detected in the brain of one of the positive animals. The sequences generated from the astrovirus strains shared low nucleotide identities in the ORF2 (< 43.7%) with other known reptilian astrovirus sequences, hinting to the massive genetic diversity of members of this viral family. Based on the partial RdRp gene of the sequenced strains, however, we observed species-specific patterns, regardless of the geographic origin of the animals, and we also identified a possible inter-species transmission event between geckoes and lizards.

Genome Sequences and Characterization of Chicken Astrovirus and Avian Nephritis Virus from Tanzanian Live Bird Markets

The enteric chicken astrovirus (CAstV) and avian nephritis virus (ANV) are the type species of the genus Avastrovirus (AAstV; Astroviridae family), capable of causing considerable production losses in poultry. Using next-generation sequencing of a cloacal swab from a backyard chicken in Tanzania, we assembled genome sequences of ANV and CAstV (6918 nt and 7318 nt in length, respectively, excluding poly(A) tails, which have a typical AAstV genome architecture (5'-UTR-ORF1a-ORF1b-ORF2-'3-UTR). They are most similar to strains ck/ANV/BR/RS/6R/15 (82.72%) and ck/CAstV/PL/G059/14 (82.23%), respectively. Phylogenetic and sequence analyses of the genomes and the three open reading frames (ORFs) grouped the Tanzanian ANV and CAstV strains with Eurasian ANV-5 and CAstV-Aii viruses, respectively. Compared to other AAstVs, the Tanzanian strains have numerous amino acid variations (substitutions, insertions and deletions) in the spike region of the capsid protein. Furthermore, CAstV-A has a 4018 nt recombinant fragment in the ORF1a/1b genomic region, predicted to be from Eurasian CAstV-Bi and Bvi parental strains. These data should inform future epidemiological studies and options for AAstV diagnostics and vaccines.

Identification of a Novel Astrovirus Associated with Bovine Respiratory Disease

Astroviruses (AstVs) cause gastrointestinal disease in mammals and avians. Emerging evidence suggests that some AstVs have extraintestinal tissue tropism, with AstVs detected in the liver, kidney, central nervous system, and the respiratory tract variably associated with disease. In cattle, AstV infection has been linked to gastroenteric or neurologic disease. Here, metagenomic sequencing of a lung from a bovine with respiratory disease identified a novel AstV with a predicted capsid-encoding ORF2 amino acid sequence with 66% identity to caprine astrovirus (CAstV G2.1). A quantitative reverse transcription PCR (qRT-PCR) targeting ORF2 found four out of 49 (8%) lungs and one out of 48 (2%) enteric samples obtained from bovine diagnostic submissions positive for the novel bovine astrovirus (BAstV). In two strongly qRT-PCR-positive lung samples, intense novel BAstV nucleic acid signals were mainly localized in the cytoplasm of alveolar macrophages and mononuclear cells using RNAscope® in situ hybridization (ISH). Genetic analysis of two novel BAstV genomes determined from qRT-PCR positive samples found high similarity for ORF1ab nucleotide sequence (92.1% and 93.9%) to BAstV strain BSRI-1, while ORF2 nucleotide sequence was most similar to CAstV G2.1 (74.6% and 77.6%). Phylogenetic analysis of the novel BAstV sequences found a close genetic relationship to the single BAstV (BSRI-1) previously identified from a bovine respiratory sample as well as bovine and caprine AstVs identified from various tissues. Further research is needed to determine the clinical significance of BAstV in respiratory diseases.

Meta-Transcriptomic Analysis Reveals Novel RNA Viruses in Hippocampus erectus

Lined seahorse, Hippocampus erectus, is an important aquatic animal due to its medicinal and ornamental purposes. However, our understanding of the viral spectrum in H. erectus is still limited. Here, we studied the viruses in H. erectus using meta-transcriptomic sequencing. A total of 213,770,166 reads were generated and assembled de novo into 539 virus-associated contigs. Three novel RNA viruses from the Astroviridae, Paramyxoviridae, and Picornaviridae families were finally identified. In addition, we identified a strain of nervous necrosis virus from H. erectus. In particular, the unhealthy group showed a higher viral diversity and abundance than the normal group. These results revealed the diversity and cross-species transmission of viruses in H. erectus and highlighted the threat of viral infections to H. erectus.

Multiplex gel-based PCR assay for the simultaneous detection of 5 genotypes of porcine astroviruses

Porcine astrovirus (PAstV) has been associated experimentally with diarrhea in piglets, but much more knowledge is needed about this virus. PAstV has high genetic variability, and 5 genotypes have been identified, namely PAstV1-5. To obtain information on the epidemiology of PAstV, we established a multiplex PAstV PCR assay to detect and differentiate the 5 PAstV genotypes simultaneously. The assay utilized specific primers for each genotype, producing fragments of 307, 353, 205, 253, and 467 bp, representing PAstV1-5, respectively. Our multiplex PCR assay amplified all 5 DNA fragments from single or mixed viral genomes without cross-reactions with other PAstV genotypes or other viruses in pigs. The limit of detection of the multiplex PCR assay was 5 × 102 copies/μL for PAstV1 and PAstV4, and 5 × 103 copies/μL for PAstV2, PAstV3, and PAstV5. We examined 76 pig fecal specimens with our multiplex PCR assay. PAstV was detected in 36 of 76 (47.4%) samples; ≥2 PAstVs were found in 20 of 76 (26.3%) samples. The multiplex PCR assay results were essentially the same as the results using a monoplex PAstV PCR assay, with a coincidence rate of >96%. Our multiplex PCR method provides a simple, sensitive, and specific detection tool for PAstV detection and epidemiologic surveys.

A peptide-based ELISA for detection of antibodies against novel goose astrovirus type 1

Goose gout disease is a high morbidity and mortality disease caused by novel serotype 1 goose astrovirus (GAstV-1), which has resulted in huge economic loss to the goose industry of China. However, few diagnostic methods have been developed for serological surveillance of GAstV-1. In our previous study, several novel B cell epitopes were identified in the ORF2 protein of GAstV-1. In this study, one novel peptide of 627-646 aa in the ORF2 recognized by monoclonal antibody (mAb) 6C6 was used as an antigen to develop an efficient peptide-based ELISA (pELISA) for detection of antibodies against GAstV-1. Specificity analysis showed that the pELISA only reacted with sera against GAstV-1, but not with sera against other pathogens tested. The sensitivity of the pELISA in detecting positive sera was higher than that of the IFA (Indirect immunofluorescence assay). The coefficients of variation (CV) of the intra-assay and inter-assay were both < 10%, indicating that the reproducibility of pELISA was good. For detection of clinical samples, the pELISA had 87.5% concordance with the IFA. Our data demonstrate that the pELISA generated here provides an accurate, rapid, and economical method for the detection antibodies against GAstV-1 for serological surveillance.

Discovery of novel Mamastroviruses in Bactrian camels and dromedaries reveals complex recombination history

Virus emergence may occur through interspecies transmission and recombination of viruses coinfecting a host, with potential to pair novel and adaptive gene combinations. Camels are known to harbor diverse ribonucleic acid viruses with zoonotic and epizootic potential. Among them, astroviruses are of particular interest due to their cross-species transmission potential and endemicity in diverse host species, including humans. We conducted a molecular epidemiological survey of astroviruses in dromedaries from Saudi Arabia and Bactrian camels from Inner Mongolia, China. Herein, we deployed a hybrid sequencing approach coupling deep sequencing with rapid amplification of complementary deoxyribonucleic acid ends to characterize two novel Bactrian and eight dromedary camel astroviruses, including both partial and complete genomes. Our reported sequences expand the known diversity of dromedary camel astroviruses, highlighting potential recombination events among the astroviruses of camelids and other host species. In Bactrian camels, we detected partially conserved gene regions bearing resemblance to human astrovirus types 1, 4, and 8 although we were unable to recover complete reading frames from these samples. Continued surveillance of astroviruses in camelids, particularly Bactrian species and associated livestock, is highly recommended to identify patterns of cross-species transmission and to determine any epizootic threats and zoonotic risks posed to humans. Phylogenomic approaches are needed to investigate complex patterns of recombination among the astroviruses and to infer their evolutionary history across diverse host species.

Candida albicans-enteric viral interactions-The prostaglandin E2 connection and host immune responses

The human microbiome comprises trillions of microorganisms residing within different mucosal cavities and across the body surface. The gut microbiota modulates host susceptibility to viral infections in several ways, and microbial interkingdom interactions increase viral infectivity within the gut. Candida albicans, a frequently encountered fungal species in the gut, produces highly structured biofilms and eicosanoids such as prostaglandin E₂ (PGE₂), which aid in viral protection and replication. These biofilms encompass viruses and provide a shield from antiviral drugs or the immune system. PGE₂ is a key modulator of active inflammation with the potential to regulate interferon signaling upon microbial invasion or viral infections. In this review, we raise the perspective of gut interkingdom interactions involving C. albicans and enteric viruses, with a special focus on biofilms, PGE₂, and viral replication. Ultimately, we discuss the possible implications of C. albicans-enteric virus associations on host immune responses, particularly the interferon signaling pathway.

Establishing farm dust as a useful viral metagenomic surveillance matrix

Farm animals may harbor viral pathogens, some with zoonotic potential which can possibly cause severe clinical outcomes in animals and humans. Documenting the viral content of dust may provide information on the potential sources and movement of viruses. Here, we describe a dust sequencing strategy that provides detailed viral sequence characterization from farm dust samples and use this method to document the virus communities from chicken farm dust samples and paired feces collected from the same broiler farms in the Netherlands. From the sequencing data, Parvoviridae and Picornaviridae were the most frequently found virus families, detected in 85-100% of all fecal and dust samples with a large genomic diversity identified from the Picornaviridae. Sequences from the Caliciviridae and Astroviridae familes were also obtained. This study provides a unique characterization of virus communities in farmed chickens and paired farm dust samples and our sequencing methodology enabled the recovery of viral genome sequences from farm dust, providing important tracking details for virus movement between livestock animals and their farm environment. This study serves as a proof of concept supporting dust sampling to be used in viral metagenomic surveillance.

Diversity of Astrovirus in Goats in Southwest China and Identification of Two Novel Caprine Astroviruses

A total of 232 goat fecal samples (124 diarrheic and 108 nondiarrheic) collected from 12 farms in Southwest China were tested for astrovirus using RT-PCR. A total of 16.9% (21/124) of diarrheic and 20.4% (22/108) of nondiarrheic samples were astrovirus-positive, and no statistical difference was found in the detection rate between healthy and sick goats. Furthermore, 28 obtained complete ORF2 sequences could be classified into six genotypes according to the species classification criteria of the International Committee on Taxonomy of Viruses (ICTV). It is worth noting that, in addition to four known caprine astrovirus genotypes (MAstV-33, MAstV-34, Caprine Astrovirus G5.1, and Caprine Astrovirus G3.1), MAstV-13 and MAstV-24 genotypes were identified in goats. Interestingly, five of 19 ORF2 sequences in the Caprine Astrovirus G3.1 genotype showed possible intragenotypic recombination events. Furthermore, nearly complete caprine astrovirus genomes of MAstV-13 and MAstV-24 genotypes were obtained. The genome of the SWUN/ECJK3/2021 strain shared the highest similarity (62.0% to 73.9%) with astrovirus in MAstV-13, and clustered in the so-called human-mink-ovine (HMO) clade, which contained the majority of the neurotropic astrovirus strains. Moreover, the SWUN/LJK2-2/2020 strain showed the highest similarity (69.7% to 78.6%) and the closest genetic relationship to the known porcine and bovine astroviruses in MAstV-24. In conclusion, this study confirmed six genotypes of astrovirus circulating among goats in Southwest China, including MAstV-13 and MAstV-24 genotypes. These findings enhance our knowledge of the prevalence and diversity of astroviruses. IMPORTANCE Caprine astrovirus is a newly emerging virus, and information regarding its prevalence and molecular characteristics remains limited. In this study, six genotypes of astrovirus, including MAstV-13 and MAstV-24, were identified in goats, adding two novel caprine astrovirus genotypes to the four previously known genotypes, thereby enriching the diversity of the caprine astrovirus. Moreover, genomes of MAstV-13 SWUN/ECJK3/2021 and MAstV-24 SWUN/LJK2-2/2020 strains were obtained from goats, which aids in the understanding of the infection spectrum and host range of the two genotypes. This study is the first to demonstrate the presence of neurotropic-like astrovirus (MAstV-13) in goats, which has significant implications for the diagnosis of neurological diseases in goats.

Metagenomic analysis of viral diversity and a novel astroviruse of forest rodent

Background

Rodents are important virus reservoirs and natural hosts for multiple viruses. They are one of the wild animals that are extremely threatening to the spread of human viruses. Therefore, research on rodents carrying viruses and identifying new viruses that rodents carry is of great significance for preventing and controlling viral diseases.

Methods

In this study, fecal samples from six species of forest rodents in Northeast China were sequenced using metagenomics, and an abundance of virome information was acquired. Selection of important zoonotic in individual rodents for further sequence and evolutionary analysis.

Results

Among the top 10 most abundant viral families, RNA virus include Orthomyxoviridae, Picornaviridae, Bunyaviridae and Arenaviridae, DNA virus include Herpesviridae, Insect virus include Nodaviridae and Baculoviridae, Plant virus Tombusviridae and Phage (Myoriviridae). Except for Myoviridae, there was no significant difference in the abundance of virus families in the feces of each rodent species. In addition, a new strain of astrovirus was discovered, with an ORF and genome arrangement comparable to other rodent astroviruses.The newly identified astrovirus had the highest similarity with the rodent astrovirus isolate, CHN/100.

Conclusions

The data obtained in this study provided an overview of the viral community present in these rodent fecal samples, revealing some rodent-associated viruses closely related to known human or animal pathogens. Strengthening our understanding of unclassified viruses harbored by rodents present in the natural environment could provide scientific guidance for preventing and controlling new viral outbreaks that can spread via rodents.

Global public health implications of human exposure to viral contaminated water

Enteric viruses are common waterborne pathogens found in environmental water bodies contaminated with either raw or partially treated sewage discharge. Examples of these viruses include adenovirus, rotavirus, noroviruses, and other caliciviruses and enteroviruses like coxsackievirus and polioviruses. They have been linked with gastroenteritis, while some enteric viruses have also been implicated in more severe infections such as encephalitis, meningitis, hepatitis (hepatitis A and E viruses), cancer (polyomavirus), and myocarditis (enteroviruses). Therefore, this review presents information on the occurrence of enteric viruses of public health importance, diseases associated with human exposure to enteric viruses, assessment of their presence in contaminated water, and their removal in water and wastewater sources. In order to prevent illnesses associated with human exposure to viral contaminated water, we suggest the regular viral monitoring of treated wastewater before discharging it into the environment. Furthermore, we highlight the need for more research to focus on the development of more holistic disinfection methods that will inactivate waterborne viruses in municipal wastewater discharges, as this is highly needed to curtail the public health effects of human exposure to contaminated water. Moreover, such a method must be devoid of disinfection by-products that have mutagenic and carcinogenic potential.

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.

Genetic diversity and pathogenicity of novel chicken astrovirus in China

AbstractFive novel chicken astrovirus (CAstV) strains, designated ZDF, MHC, WSC, WSW and MHW, were successfully isolated from chickens with gout and were subjected to full genome sequencing characterization and tested for their pathogenic effects on Specific pathogen free (SPF) chicken embryos and chickens. The complete genomes of the 5 isolated strains were approximately 7436 nt to 7511 nt in length. Phylogenetic analysis revealed that strains ZDF and MHC were clustered in a clade with strains isolated in China and that the others were clustered with strains from other countries. Based on the amino acids of ORF2, strains MHW and WSW belonged to subgroup Ai, strain WSC belonged to Bii, and strains ZDF and MHC belonged to Bi. The pathogenicity of strains MHW, MHC and WSC belonging to different subgroups was studied. The results showed that the mortality of the chicken embryos was 100% when infected with any strain more than 10³ TCID₅₀, 35% in SPF chickens infected with strain WSC, 25% with MHC and 15% with MHW. The body weights of chickens infected and embryos infected with 0.2 mL 10 TCID₅₀ were significantly reduced after hatching. SPF chickens infected with any of the strains had similar lesions characterized by urate deposits on the epicardium and kidney and necrotic spots on the liver. This study identified the three kinds of genotypic CAstV prevalent in China, with high mortality in embryonated chicken eggs and leading to white chick syndrome, retarded growth and visceral gout in infected chicks.

Detection of multiple human astroviruses in sewage by next generation sequencing

Human astrovirus (HAstV) composes of classic HAstV serotypes 1-8 and recently discovered novel HAstV-MLB and HAstV-VA strains. A number of studies have demonstrated that wastewater analysis is an effective approach to understand the prevalence and diversity of enteric viruses in local population. However, a comprehensive analysis of classic and novel HAstVs in sewage is still lacking. In this study, sewage samples were collected monthly from Jinan, China during 2018-2019. Quantification of HAstV genomes was performed by real-time quantitative PCR. Different from previous studies which focused on partial ORF1b or ORF2 gene, complete ORF2 region of HAstV was amplified from sewage concentrates, and amplicons were subjected to next generation sequencing (NGS) and genetic analysis. This methodology allowed detection of 18 astroviruses, of which 7 (HAstV-1, -2, -4, -5, VA1, VA2, and VA3) were detected in all sewage samples. A new strain VA6 mapped to the HMO clade was identified in 20.8% of samples, with 82.4%-83.3% nucleotide identities to the closest strain VA5. The viral load of classic, MLB and VA clades in sewage samples ranged from 3.7 × 10⁴ to 4.6 × 10⁷, 3.4 × 10⁴ to 3.9 × 10⁶, and 3.3 × 10⁴ to 4.1 × 10⁶ copies per liter, respectively. Phylogenetic analysis based on complete ORF2 region reflected local HAstVs within each genotype constituted multiple co-circulating lineages. Existence of several new lineages composed exclusively or predominantly of Chinese sequences was observed as well. These results demonstrate sewage contains astroviruses with considerable high diversities. NGS based environmental surveillance greatly improves the understanding of HAstV circulation and should be encouraged.

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.

Discovery of novel DNA viruses in small mammals from Kenya

Emergence and re-emergence of infectious diseases of wildlife origin have led pre-emptive pathogen surveillances in animals to be a public health priority. Rodents and shrews are among the most numerically abundant vertebrate taxa and are known as natural hosts of important zoonotic viruses. Many surveillance programs focused more on RNA viruses. In comparison, much less is known about DNA viruses harbored by these small mammals. To fill this knowledge gap, tissue specimens of 232 animals including 226 rodents, five shrews and one hedgehog were collected from 5 counties in Kenya and tested for the presence of DNA viruses belonging to 7 viral families by PCR. Diverse DNA sequences of adenoviruses, adeno-associated viruses, herpesviruses and polyomaviruses were detected. Phylogenetic analyses revealed that most of these viruses showed distinction from previously described viruses and formed new clusters. Furthermore, this is the first report of the discovery and full-length genome characterization of a polyomavirus in Lemniscomys species. This novel polyomavirus, named LsPyV KY187, has less than 60% amino acid sequence identity to the most related Glis glis polyomavirus 1 and Sciurus carolinensis polyomavirus 1 in both large and small T-antigen proteins and thus can be putatively allocated to a novel species within Betapolyomavirus. Our findings help us better understand the genetic diversity of DNA viruses in rodent and shrew populations in Kenya and provide new insights into the evolution of those DNA viruses in their small mammal reservoirs. It demonstrates the necessity of ongoing pathogen discovery studies targeting rodent-borne viruses in East Africa.

Bovine Astrovirus—A Comprehensive Review

Bovine astrovirus (BoAstV) is a small non-enveloped virus with a single-stranded positive-sense RNA. In 1978, BoAstV was first found in calf diarrhea fecal samples in the United Kingdom and since then it has been reported in many other countries. It has wide tissue tropism and can infect multiple organs, including the intestine, nerves and respiratory tract. Since BoAstV is prevalent in healthy as well as clinically infected bovines, and is mostly associated with co-infection with other viruses, the pathogenic nature of BoAstV is still unclear. At present, there are no stable passage cell lines available for the study of BoAstV and animal model experiments have not been described. In addition, it has been reported that BoAstV may have the possibility of cross-species transmission. This review summarizes the current state of knowledge about BoAstV, including the epidemiology, evolution analysis, detection methods, pathogenesis and potential cross species transmission, to provide reference for further research of BoAstV.

Interaction between MHC diversity and constitution, gut microbiota and Astrovirus infections in a neotropical bat

Astroviruses (AstVs) infect numerous mammalian species including reservoirs such as bats. Peptides encoded by the genes of the highly polymorphic Major Histocompatibility Complex (MHC) form the first line of host defence against pathogens. Aside from direct involvement in mounting adaptive immune responses, MHC class II genes are hypothesized to regulate gut commensal diversity and shape the production of immune-modulatory substances by microbes, indirectly affecting host susceptibility. Despite initial empirical evidence for the link between host MHC and the microbiota, associations among these factors remain largely unknown. To fill this gap, we examined MHC allelic diversity and constitution, the gut bacterial community and abundance pattern of a wild population of the neotropical bat (Artibeus jamaicensis) challenged by AstV infections. First, we show an age-dependent relationship between the host MHC class II diversity and constitution and the gut microbiota in AstV uninfected bats. Crucially, these associations changed in AstV infected bats. Additionally, we identify changes in abundance of specific bacterial taxa linked to the presence of certain MHC supertypes and AstV infection. We suggest changes in the microbiota to be either a result of AstV infection or the MHC-mediated modulation of microbial communities. The latter could subsequently affect microbe-mediated immunity and resistance against AstV infection. Our results underscore that the reciprocal nature of host immune genetics, gut microbial diversity and pathogen infection requires attention, which is particularly important given its repercussions for disease susceptibility and severity in wild animal populations with a history of zoonotic spillover and frequent human contact.