Complete sequence of a novel duck astrovirus

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.

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.

Detection and Molecular Characterization of Enteric Viruses in Poultry Flocks in Hebei Province, China

Simple Summary

Enteric viruses act as etiological agents for a series of health disturbances that pose a threat to commercial chickens worldwide. The affected chickens exhibit stunted growth, low feed conversion, etc. On a global scale, research on enteric virus diversity has been performed in countries such as India, South Korea and Brazil, yet at present, there have been no conclusive reports of avian enteric viruses in China. In the present study, the virus species, infection types, clinical symptoms, and relationships among the virus species were studied in 145 positive enteric virus samples. Additionally, the evolutionary relationship and recombination of the viruses were also further studied. The results of this study can be used to define the distribution and infection type of enteric viruses in poultry, and to analyze the classification of and evolutionary relationship between certain viruses.

Abstract

Enteric viruses, as a potential pathogen, have been found to be vital causes of economic losses in poultry industry worldwide. The enteric viruses widely studied to date mainly include avian nephritis virus (ANV), avian reovirus (ARe), chicken astrovirus (CAstV), chicken parvovirus (ChPV), fowl adenovirus group I (FAdV-1), infectious bronchitis virus (IBV), and avian rotavirus (ARoV). This paper aimed to identify single and multiple infections of the seven enteric viruses using the data obtained from positive 145 enteric virus samples in poultry flocks from different areas in Hebei Province, throughout the period from 2019 to 2021. Next, the correlation between bird age and clinical signs was investigated using PCR and RT-PCR techniques. Furthermore, the whole genomes of seven parvovirus strains and open reading frame 2 (ORF2) of six CAstV strains and eight ANV strains were sequenced for phylogenetic analysis and recombination analysis, to characterize the viruses and evaluate species correlation and geographic patterns. A total of 11 profiles of virus combinations were detected; 191 viruses were detected in 145 samples; 106 single infections were reported in 73.1% of the samples; and multiple infections were detected in the remaining 26.9%. For viruses, 69% of ChPV was correlated with single infection, while ANV (61.4%) and CAstV (56.1%) were correlated with multiple infections. However, IBV and ARe were not detected in any of the samples. Recombination events were reported in parvovirus, and all CAstV sequences investigated in this paper were included within genotype Bii. The eight ANV strains pertained to different subtypes with significant differences. The above results revealed for the first time the complexity of enteric viruses over the past several years, thus contributing to disease prevention and control in the future.

A proposed disease classification system for duck viral hepatitis

The nomenclature of duck viral hepatitis (DVH) was historically not a problem. However, 14 hepatotropic viruses among 10 different genera are associated with the same disease name, DVH. Therefore, the disease name increasingly lacks clarity and may no longer fit the scientific description of the disease. Because one disease should not be attributed to 10 genera of viruses, this almost certainly causes misunderstanding regarding the disease-virus relationship. Herein, we revisited the problem and proposed an update to DVH disease classification. This classification is based on the nomenclature of human viral hepatitis and the key principle of Koch's postulates (“one microbe and one disease”). In total, 10 types of disease names have been proposed. These names were literately matched with hepatitis-related viruses. We envision that this intuitive nomenclature system will facilitate scientific communication and consistent interpretation in this field, especially in the Asian veterinary community, where these diseases are most commonly reported.

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.

Surveillance and genetic diversity analysis of avian astrovirus in China

Avian astroviruses (AAstVs) have caused major problem for poultry breeding industries in China in recent years, and the goose gout caused by goose astrovirus has produced particularly great economic losses. To better understand the prevalence and genetic diversity of AAstVs in China, 1210 poultry samples collected from eight provinces were tested with reverse transcription-polymerase chain reaction (RT-PCR) to detect AAstV infections in different poultry populations. Then, Open reading frames 2 (ORF2) was amplified by specific primers, and the genetic evolution was analyzed. Our surveillance data demonstrate the diversity of AAstVs in China insofar as we detected 17 AAstVs, including seven chicken astroviruses (CAstVs), five avian nephritis viruses (ANVs), two goose astroviruses (GoAstVs), two duck astrovirus (DAstVs), and one new AAstV belonging to Avastrovirus Group 3. The positive rate of AAstV infection was 1.40%. Host analysis showed that CAstVs and ANVs were isolated from chickens, DAstVs and GoAstVs were isolated from ducks. Host-species-specific AAstVs infections were also identified in numerous samples collected at each stage of production. This study provides further evidence to better understand the epidemiology of AAstVs in different species of poultry in China.

Establishment of duplex SYBR Green I-based real-time PCR assay for simultaneous detection of duck hepatitis a virus-1 and duck astrovirus-3

Duck viral hepatitis (DVH) mainly affects ducklings under 1 month of age, causes liver necrosis, enlargement, and hemorrhage, and is highly lethal, seriously jeopardizing the duck industry. The prevalence of serotypes DHAV-1 and DAstV-3 is increasing, and co-infection is common. Moreover, the similar clinical characteristics of the DHAV-1 and DAstV-3 infections and high frequency of co-infection make diagnosis difficult. In this study, to establish a method for the rapid simultaneous detection of DHAV-1 and DAstV-3 , two pairs of specific primers were designed according to their conserved gene regions. A SYBR Green I-based real-time PCR assay was successfully established that can quickly and differentially detect the two viruses. Moreover, the assay is highly specific and does not show cross-reaction with other common viruses. The detection limit of the method is 7.34 × 10 1 copies/μL and 3.78 × 10 1 copies/μL for DHAV-1 and DAstV-3, respectively, indicating high sensitivity. A total of 34 clinical samples were tested using the established method; the positive rates for DHAV-1 and DAstV-3 was 14.71% and 8.82%, respectively, and that for co-infection was 2.94% (1/34), which was better than that obtained with conventional PCR. In summary, the SYBR Green I-based real-time PCR assay established in this study has high specificity, good sensitivity and accuracy, high feasibility, and is rapid. Thus, it can be a powerful tool for the co-infection detection of DHAV-1 and DAstV-3 and for future epidemiological studies.

Metagenomic characterisation of additional and novel avian viruses from Australian wild ducks

Birds, notably wild ducks, are reservoirs of pathogenic and zoonotic viruses such as influenza viruses and coronaviruses. In the current study, we used metagenomics to detect and characterise avian DNA and RNA viruses from wild Pacific black ducks, Chestnut teals and Grey teals collected at different time points from a single location. We characterised a likely new species of duck aviadenovirus and a novel duck gyrovirus. We also report what, to the best of our knowledge, is the first finding of an avian orthoreovirus from Pacific black ducks and a rotavirus F from Chestnut teals. Other viruses characterised from the samples from these wild ducks belong to the virus families Astroviridae, Caliciviridae and Coronaviridae. Some of the viruses may have potential cross-species transmissibility, while others indicated a wide genetic diversity of duck viruses within a genus. The study also showed evidence of potential transmission of viruses along the East Asian-Australasian Flyway; potentially facilitated by migrating shorebirds. The detection and characterisation of several avian viruses not previously described, and causing asymptomatic but potentially also symptomatic infections suggest the need for more virus surveillance studies for pathogenic and potential zoonotic viruses in wildlife reservoirs.

Genomic and phylogenetic characteristics of a novel goose astrovirus in Anhui Province, Central-Eastern China

Goose astrovirus (GAstV) causes a novel disease characterized by urate deposition in the viscera and joints in goslings in many provinces of China, leading to huge economic losses in the goose industry. To better understand the genetic diversity of GAstV in the Anhui Province, Central-Eastern China, 48 kidney samples from goslings with gout were subjected to reverse-transcription polymerase chain reaction (RT-PCR) analysis for detecting GAstV, and phylogenetic analysis of whole genomes and ORFs was performed. Thirty-five samples were GAstV-positive, indicating that the virus is a frequent cause of gout. The whole genomes of 5 GAstV strains were successfully sequenced and named AHAU1-5. The sequenced genomes and those of reference GAstV strains in GenBank displayed 97.4-99.8% similarity. The isolates had high nucleotide sequence similarity with the GAstV reference strain SDPY. A phylogenetic analysis showed that AHAU1 and AHAU4 were closely related to the reference strain SDPY; AHAU2, AHAU3, and AHAU5 formed separate branches. Furthermore, recombination analysis revealed putative recombination sites in the Jiangsu strains that originated from strains in the Anhui and Shandong Provinces, accompanied by the recombination of different strains in the Anhui Province. This study is the first to carry out systematic phylogenetic analysis of GAstV isolated in the Anhui Province, Central-Eastern China. By improving our understanding of the diversity of GAstV in the Anhui Province, these results provide a basis for the prevention and control of its spread.

Complete genome sequence and phylogenetic analysis of novel avastroviruses circulating in China from 2016 to 2018

Avastrovirus-specific antibodies are widely detected in chickens in China. However, there are currently no commercially available vaccines for this group of viruses. To address this issue, we collected 76 tissue samples from Avastrovirus (AAstVs) antibody-positive chickens from farms across eight provinces in China from 2016 to 2018. The samples were then screened for the presence of AAstVs sequences by polymerase chain reaction analysis and a phylogenetic tree was constructed. Specific primers were designed to amplify the whole genome sequences of the viruses from four positive samples, with the genetic characteristics and structures of the resulting genomes then analyzed further. Overall, 42 (55.3 %) of the 76 samples were positive for AAstVs RNA. Phylogenetic analysis along with the ORF1b gene showed that 15 isolates were grouped in AAstV-1 and 27 of them were grouped in AAstV-2. None of the isolates was belonged to AAstV-3. Sequencing and structural analyses revealed that the genomes of the four isolates showed the typical characteristics of AAstVs genomes but were genetically distinct from other AAstVs. The results of this study will contribute to our understanding of the genetic characteristics of AAstVs in China.

A novel group of avian astroviruses from Neotropical passerine birds broaden the diversity and host range of Astroviridae

Metagenomics is helping to expand the known diversity of viruses, especially of those with poorly studied hosts in remote areas. The Neotropical region harbors a considerable diversity of avian species that may play a role as both host and short-distance vectors of unknown viruses. Viral metagenomics of cloacal swabs from 50 Neotropical birds collected in French Guiana revealed the presence of four complete astrovirus genomes. They constitute an early diverging novel monophyletic clade within the Avastrovirus phylogeny, representing a putative new astrovirus species (provisionally designated as Avastrovirus 5) according to the International Committee on Taxonomy of Viruses (ICTV) classification criteria. Their genomic organization shares some characteristics with Avastrovirus but also with Mamastrovirus. The pan-astrovirus RT-PCR analysis of the cloacal samples of 406 wild Neotropical birds showed a community-level prevalence of 4.9% (5.1% in passerines, the highest described so far in this order of birds). By screening birds of a remote region, we expanded the known host range of astroviruses to the avian families Cardinalidae, Conopophagidae, Furnariidae, Thamnophilidae, Turdidae and Tyrannidae. Our results provide important first insights into the unexplored viral communities, the ecology, epidemiology and features of host-pathogen interactions that shape the evolution of avastroviruses in a remote Neotropical rainforest.

Isolation and genomic characterization of gosling gout caused by a novel goose astrovirus

A severe infectious disease characterized with gout, haemorrhage and swellings of kidneys has affected goslings around the major goose-producing regions in China since November 2016. A Novel goose-origin astrovirus (AStV), designated as AStV/SDPY/Goose/1116/17 (AStV-SDPY) strain, was isolated from diseased goslings, and experimental reproduction of gout was successful using the AStV-SDPY strain. Additionally, the AStV-SDPY was conducted for its full genome sequencing characterization using next-generation sequencing (NGS) technique on Illumina HiSeq platform. A complete genome of the AStV-SDPY was 7,252 nt in length and encoded three viral proteins. Phylogenetic analysis revealed that AStV-SDPY strain belongs to an independent branch of avian astroviruses, and the nucleotide homology among AStV-SDPY and other classic avian astrovirus strains was only 48.8%-68.2%. Results of above data indicated the causative agent of the gosling gout occurring in China is a novel divergent goose astrovirus.

Genetic characterization of a novel group of avastroviruses in geese

As part of aetiological studies, we tested 28 samples collected from domestic geese showing enteritis and sporadic death. A novel group of avastroviruses was found in six samples. One isolate was completely sequenced, which comprised 7,148 nucleotides. Pairwise comparisons and phylogenetic analysis demonstrated that the goose astrovirus is highly divergent from all previously described avastroviruses. Our data support the view that domestic geese can be infected by astroviruses with different genetic backgrounds, and have raised a concern about the role of domestic geese as reservoirs for diverse astroviruses.

A novel group of avian Avastrovirus in domestic geese, China

Using an ORF1b-based astrovirus-specfic reverse transcription (RT)-PCR assay, a novel astrovirus-like was detected from domestic geese in China. Pairwise comparisons and phylogenetic analyzes suggested that a novel group of goose astrovirus, different with previously known astroviruses in the genus Avastrovirus, was found circulating in geese. This study has expanded our understanding about the role of domestic waterfowls as reservoirs for diverse astroviruses.

Hepatitis Virus Infections in Poultry

Viral hepatitis in poultry is a complex disease syndrome caused by several viruses belonging to different families including avian hepatitis E virus (HEV), duck hepatitis B virus (DHBV), duck hepatitis A virus (DHAV-1, -2, -3), duck hepatitis virus Types 2 and 3, fowl adenoviruses (FAdV), and turkey hepatitis virus (THV). While these hepatitis viruses share the same target organ, the liver, they each possess unique clinical and biological features. In this article, we aim to review the common and unique features of major poultry hepatitis viruses in an effort to identify the knowledge gaps and aid the prevention and control of poultry viral hepatitis. Avian HEV is an Orthohepevirus B in the family Hepeviridae that naturally infects chickens and consists of three distinct genotypes worldwide. Avian HEV is associated with hepatitis-splenomegaly syndrome or big liver and spleen disease in chickens, although the majority of the infected birds are subclinical. Avihepadnaviruses in the family of Hepadnaviridae have been isolated from ducks, snow geese, white storks, grey herons, cranes, and parrots. DHBV evolved with the host as a noncytopathic form without clinical signs and rarely progressed to chronicity. The outcome for DHBV infection varies by the host's ability to elicit an immune response and is dose and age dependent in ducks, thus mimicking the pathogenesis of human hepatitis B virus (HBV) infections and providing an excellent animal model for human HBV. DHAV is a picornavirus that causes a highly contagious virus infection in ducks with up to 100% flock mortality in ducklings under 6 wk of age, while older birds remain unaffected. The high morbidity and mortality has an economic impact on intensive duck production farming. Duck hepatitis virus Types 2 and 3 are astroviruses in the family of Astroviridae with similarity phylogenetically to turkey astroviruses, implicating the potential for cross-species infections between strains. Duck astrovirus (DAstV) causes acute, fatal infections in ducklings with a rapid decline within 1-2 hr and clinical and pathologic signs virtually indistinguishable from DHAV. DAstV-1 has only been recognized in the United Kingdom and recently in China, while DAstV-2 has been reported in ducks in the United States. FAdV, the causative agent of inclusion body hepatitis, is a Group I avian adenovirus in the genus Aviadenovirus. The affected birds have a swollen, friable, and discolored liver, sometimes with necrotic or hemorrhagic foci. Histologic lesions include multifocal necrosis of hepatocytes and acute hepatitis with intranuclear inclusion bodies in the nuclei of the hepatocytes. THV is a picornavirus that is likely the causative agent of turkey viral hepatitis. Currently there are more questions than answers about THV, and the pathogenesis and clinical impacts remain largely unknown. Future research in viral hepatic diseases of poultry is warranted to develop specific diagnostic assays, identify suitable cell culture systems for virus propagation, and develop effective vaccines.

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

Astroviruses are a diverse family of viruses that infect a wide range of mammalian and avian hosts. Here we describe the phylogenetic diversity and current classification methodology of astroviruses based on the ORF1b and ORF2 genes, highlighting the propensity of astroviruses to undergo interspecies transmission and genetic recombination which greatly increase diversity and complicate attempts at a unified and comprehensive classification strategy.

Isolation and detection of duck astrovirus CPH: implications for epidemiology and pathogenicity

The transmission routes of duck astrovirus CPH (DAstV/CPH) and its pathogenicity in duck embryos were investigated. Using a reverse transcription-polymerase chain reaction (RT-PCR) developed in this study, DAstV/CPH was detected in 23/50 fresh droppings of breeder ducks, 39/65 breeding eggs, 26/31 dead embryos, and 6/10 newly hatched ducklings, which were taken from a Pekin duck farm where DAstV/CPH had previously been identified. This finding, and the detection of DAstV/CPH in 36/130 dead-in-shell duck embryo samples collected from different hatcheries located in six provinces, suggests that the virus may be horizontally and vertically transmitted and associated with hatchability problems. Inoculation and repeated passages in embryonating duck eggs resulted in isolation of DAstV/CPH. The virus caused severe chorioallantoic membrane lesions as well as growth retardation and embryo mortality, indicating that DAstV/CPH is pathogenic for duck embryos. The effect of DAstV/CPH on hatching was confirmed by an embryo infection experiment in which 8/10 9-day-old duck embryos inoculated with the third passage of DAstV/CPH were unable to hatch, with most embryos succumbing in the final stage of incubation. The use of RT-PCR on the hatched ducklings provided evidence that the embryos could develop into infected ducklings.

Complete genome sequence analysis of chicken astrovirus isolate from India

Objective

Chicken astroviruses have been known to cause severe disease in chickens leading to increased mortality and “white chicks” condition. Here we aim to characterize the causative agent of visceral gout suspected for astrovirus infection in broiler breeder chickens.

Methods

Total RNA isolated from allantoic fluid of SPF embryo passaged with infected chicken sample was sequenced by whole genome shotgun sequencing using ion-torrent PGM platform. The sequence was analysed for the presence of coding and non-coding features, its similarity with reported isolates and epitope analysis of capsid structural protein.

Results

The consensus length of 7513 bp genome sequence of Indian isolate of chicken astrovirus was obtained after assembly of 14,121 high quality reads. The genome was comprised of 13 bp 5′-UTR, three open reading frames (ORFs) including ORF1a encoding serine protease, ORF1b encoding RNA dependent RNA polymerase (RdRp) and ORF2 encoding capsid protein, and 298 bp of 3′-UTR which harboured two corona virus stem loop II like “s2m” motifs and a poly A stretch of 19 nucleotides. The genetic analysis of CAstV/INDIA/ANAND/2016 suggested highest sequence similarity of 86.94% with the chicken astrovirus isolate CAstV/GA2011 followed by 84.76% with CAstV/4175 and 74.48%% with CAstV/Poland/G059/2014 isolates. The capsid structural protein of CAstV/INDIA/ANAND/2016 showed 84.67% similarity with chicken astrovirus isolate CAstV/GA2011, 81.06% with CAstV/4175 and 41.18% with CAstV/Poland/G059/2014 isolates. However, the capsid protein sequence showed high degree of sequence identity at nucleotide level (98.64-99.32%) and at amino acids level (97.74–98.69%) with reported sequences of Indian isolates suggesting their common origin and limited sequence divergence. The epitope analysis by SVMTriP identified two unique epitopes in our isolate, seven shared epitopes among Indian isolates and two shared epitopes among all isolates except Poland isolate which carried all distinct epitopes.

Electronic supplementary material

The online version of this article (doi:10.1007/s11259-016-9673-6) contains supplementary material, which is available to authorized users.

Novel human astroviruses: Novel human diseases?

Astroviruses are small, non-enveloped, single-stranded positive RNA viruses that belong to the Astroviridae family. While classical human astroviruses (HAstV) are a well-recognized cause of acute non-bacterial diarrhea among young children worldwide, novel astroviruses, named HAstV-MLB and HAstV-VA/HMO, have been identified recently in humans by molecular assays. They are phylogenetically more related to animal astroviruses than to classical human astroviruses, thus suggesting cross-species transmission. Serological studies demonstrated a surprisingly high seroprevalence in certain populations and highlighted a high infection rate in the early years of life. Although their pathogenic role has not yet been clearly determined, novel astrovirus RNA sequences have been identified in different biological specimens of symptomatic patients, including the feces, plasma, cerebrospinal fluid, and brain biopsies. Thus, there is evidence that they could contribute not only to digestive tract infection, but also to unexpected clinical syndromes, notably encephalitis and meningitis. Severe infections affect mainly immunocompromised patients. These findings indicate that novel astroviruses should be considered in the differential diagnosis of immunocompromised patients with meningitis or encephalitis of unknown origin.

Nearly full-length genome sequence of a novel astrovirus isolated from chickens with 'white chicks' condition

Avian astroviruses (aAstVs) are divided into three species, Avastrovirus 1, Avastrovirus 2, and Avastrovirus 3, but there are a few strains are waiting to be assigned to an official taxonomic group. This study presents the molecular characterization of chicken astrovirus (CAstV), PL/G059/2014, which is involved in the induction of “white chicks” condition. The 7382-nucleotide-long genome sequence was determined by next-generation sequencing using an Illumina MiSeq System. Phylogenetic analysis showed that it has the characteristics that are typical of avian astroviruses. However, overall degree of nucleotide sequence identity was 43.6 % to 73.7 % between PL/G059/2014 and other available genome sequences of aAstV strains. The amino acid sequences of the proteins encoded by ORF1a and ORF1b of the studied strain were very similar (86.5-93.8 % identity) to those of CAstVs 4175 and GA2011, but they were only 32.7-35.2 % identical in the case of ORF2, which is used officially for astrovirus species demarcation. These features could suggest that the PL/G059/2014 strain should be assigned to a new species in the genus Avastrovirus. Moreover, the different phylogenetic topology of PL/G059/2014 and its nucleotide sequence similarity in different genomic regions could suggest that a recombination event occurred during its evolution and that it has ancestors in common with duck astroviruses.