Chicken Astrovirus Research Articles

Influence of biosecurity on the occurrence of various enteric viruses in broiler flocks

ABSTRACT Common enteric viruses affecting commercial broiler flocks include fowl adenovirus (FAdV), chicken parvovirus (ChPV), chicken astrovirus (CAstV), avian reovirus (ARV) and avian rotavirus (AvRV). To investigate their prevalence and to identify single and multiple infections we collected intestinal samples from 49 Austrian broiler flocks during necropsy of dead-on-farm birds twice during a production cycle (7–14 days and 28–35 days). Altogether, up to three consecutive clinically healthy flocks without signs of gastrointestinal disease were sampled from 17 different farms. Samples were analysed using virus isolation and PCR/RT–PCR methods. Virus prevalence was correlated with production data and on-farm biosecurity and management practices. Overall, ARV (75%) was most commonly detected in the flocks, followed by CAstV (61%), ChPV (61%), FAdV (57%) and AvRV (8%). Only in three (6%) flocks were none of the investigated enteric viruses detected. Flock infection profiles were very heterogeneous and included individual detection of the investigated viruses as well as different combinations thereof (up to all five investigated viruses). Even in the absence of clinical diarrhoea and/or macroscopic intestinal lesions, statistical analysis confirmed that the number of viruses detected had a significant economic impact characterised by poor weight gain and increased mortality, particularly due to the presence of FAdV, CAstV and/or ARV. Furthermore, the use of barn-specific clothing and/or footbaths as well as regular vermin control, resulted in lower prevalence of enteric viruses in the flocks studied. This highlights the importance of common biosecurity measures in poultry production to prevent economic losses. RESEARCH HIGHLIGHTS Detection timepoints and patterns indicate horizontal introduction of various enteric viruses. Flock infection profiles were very heterogeneous; no dominating virus profile. Broiler production was negatively affected by the number of enteric viruses detected. Common biosecurity measures had a significant negative effect on virus prevalence.

Detection and genetic characterization of chicken astrovirus and avian nephritis virus from hatchery to farm

ABSTRACT Astroviruses are an emerging hazard in hatchery management, and they are responsible for great economic losses in poultry farms worldwide. Chicken astrovirus (CAstV) and avian nephritis virus (ANV) are involved in decreased hatching rate, mainly due to embryo deaths, and pale and runted chicks too weak to hatch. Hatchery diseases occur through direct egg infection or vertical transmission. However, the specific role of astroviruses in these diseases is still largely unknown. To elucidate this a high-quality Piedmont hatchery (Italy) was selected based on farm clinical signs and the astrovirus serological positivity in the breeder farm. The viral dynamics were followed from the hatchery to the farm. The presence of both CAstV and ANV was monitored by evaluating the viral load in environmental and bird samples. Interestingly, both viruses were detected in chick yolk sacs at 18 days of incubation, and in the gut contents of 1-day chicks, whereas in the hatchery environmental samples, the eggs' external surfaces and the embryos’ intestinal contents were negative. The CAstV copy number was higher in bird tissues from the hatchery, while a greater ANV load was detected in bird tissues from the farm. Moreover, our data suggest vertical transmission of both viruses. Frequent co-infection was also observed in samples from both the hatchery and the farm. Lastly, the first Italian full-length genome and molecular characterization of ANV was obtained. RESEARCH HIGHLIGHTS Identified the role of the hatchery in astrovirus transmission. Sequenced the avian nephritis virus complete genome. Investigated tissue distribution of astrovirus from egg to chicks. Demonstrated co-infection of ANV/CAstV.

First Isolation and Genetic Characterization of Avian Nephritis Virus 4 from Commercial Poultry in India.

Avian nephritis virus (ANV), which belongs to the family Astroviridae, is associated with different clinical manifestations (enteric and kidney disorders) in poultry. Despite being a significant pathogen of the avian industry worldwide, information regarding genetic features of these viruses in India is scarce. In this study, 386 intestinal samples collected from 37 slaughterhouses in two north Indian states (Rajasthan and Haryana) were screened for ANV with reverse transcription PCR (RT-PCR) targeting the conserved ORF1b gene, followed by nucleotide sequencing of the amplified product. RT-PCR and sequencing confirmed the presence of ANV in 32 clinical samples (8.29%), with concurrent infections of infectious bronchitis virus, chicken astrovirus, and fowl adenoviruses observed in some clinical samples (n = 4). Virus isolations were successful from four out of 12 ANV-positive clinical samples passaged via the yolk-sac route in specific-pathogen-free embryonated chicken eggs. Additionally, the near-complete genomes of two viruses were determined through sequencing. Phylogenetic analysis based on full-length capsid protein sequences classified the viruses into ANV genotype 4 (ANV4), and to the best of our knowledge this is the first report of ANV4 from India. This study revealed the presence and circulation of new strains of ANV in Indian poultry. Genetic profiling and isolation of the viruses in this study will not only aid in the development of diagnostic tools and vaccines for ANV but also offer valuable insights into its epidemiology.

Molecular characterization of chicken astrovirus and pathogenicity of a novel isolate in China.

As an enteric virus, chicken astrovirus has been related to various kinds of diseases in chickens, including white chick syndrome, runting-stunting syndrome, severe kidney disease, urate deposits and visceral gout, generating economic losses in the poultry industry globally. The complete ORF2 gene of 31 CAstV isolates in six provinces of China during 2020-2022 was characterized and analyzed with the purpose of better understanding the molecular epidemiology and genetic diversity of CAstV field isolates. Phylogenetic analysis which was based on the complete ORF2 (capsid) amino acid sequence of 31 CAstV isolates and 57 reference strains indicated that 2 isolates belonged to subgroup Ai, 10 isolates belonged to subgroup Bi, 3 isolates belonged to subgroup Bii, 5 isolates belonged to subgroup Biii, 7 isolates belonged to subgroup Biv, 3 isolates belonged to subgroup Bv, and one isolate (JS202103) belonged to a new B subgroup. In addition, the novel CAstV strain JS202103 was successfully isolated in vitro, and its whole genome shared 76.9-94.3% identity with the 29 CAstV reference strains. JS202103 caused hatchability reduction, dead embryos, kidney disease and visceral gout in chicken embryos. Moreover, this is the also the initial study focusing on diverse CAstV strains including subgroups Biii, Biv, and Bv circulate in China. The current work contributes to improving our understanding of CAstV isolates in China, and it will also provide references for developing efficient measures to control this virus.

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.

Virulent Newcastle disease virus genotypes V.3, VII.2, and XIII.1.1 and their coinfections with infectious bronchitis viruses and other avian pathogens in backyard chickens in Tanzania

Oropharyngeal (OP) and cloacal (CL) swabs from 2049 adult backyard chickens collected at 12 live bird markets, two each in Arusha, Dar es Salaam, Iringa, Mbeya, Morogoro and Tanga regions of Tanzania were screened for Newcastle disease virus (NDV) using reverse transcription real-time PCR (rRT-PCR). The virus was confirmed in 25.23% of the birds (n = 517; rRT-PCR CT ≤ 30), with the highest positivity rates observed in birds from Dar es Salaam region with higher prevalence during the dry season (September–November 2018) compared to the rainy season (January and April–May 2019). Next-generation sequencing of OP/CL samples of 20 out of 32 birds that had high amounts of viral RNAs (CT ≤ 25) resulted in the assembly of 18 complete and two partial genome sequences (15,192 bp and 15,045–15,190 bp in length, respectively) of NDV sub-genotypes V.3, VII.2 and XIII.1.1 (n = 1, 13 and 4 strains, respectively). Two birds had mixed NDV infections (V.3/VII.2 and VII.2/XIII.1.1), and nine were coinfected with viruses of families Astroviridae, Coronaviridae, Orthomyxoviridae, Picornaviridae, Pneumoviridae, and Reoviridae. Of the coinfecting viruses, complete genome sequences of two avastroviruses (a recombinant chicken astrovirus antigenic group-Aii and avian nephritis virus genogroup-5) and two infectious bronchitis viruses (a turkey coronavirus-like recombinant and a GI-19 virus) were determined. The fusion (F) protein F1/F2 cleavage sites of the Tanzanian NDVs have the consensus motifs 112 RRRKR↓F 117 (VII.2 strains) and 112 RRQKR↓F 117 (V.3 and XIII.1.1 strains) consistent with virulent virus; virulence was confirmed by intracerebral pathogenicity index scores of 1.66–1.88 in 1-day-old chicks using nine of the 20 isolates. Phylogenetically, the complete F-gene and full genome sequences regionally cluster the Tanzanian NDVs with, but distinctly from, other strains previously reported in eastern and southern African countries. These data contribute to the understanding of NDV epidemiology in Tanzania and the region.

MiRNA Expression Signatures Induced by Chicken Astrovirus Infection in Chickens.

miRNAs represent ubiquitous regulators of gene expression and play an important and pivotal regulatory role in viral disease pathogenesis and virus-host interactions. Although previous studies have provided basic data for understanding the role of miRNAs in the molecular mechanisms of viral infection in birds, the role of miRNAs in the regulation of host responses to chicken astrovirus (CAstV) infection in chickens is not yet understood. In our study, we applied next-generation sequencing to profile miRNA expression in CAstV-infected chickens and to decipher miRNA-targeted specific signaling pathways engaged in potentially vital virus-infection biological processes. Among the 1354 detected miRNAs, we identified 58 mature miRNAs that were significantly differentially expressed in infected birds. Target prediction resulted in 4741 target genes. GO and KEGG pathway enrichment analyses showed that the target genes were mainly involved in the regulation of cellular processes and immune responses.

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.

Chicken Astro virus (CAstV): Isolation and characterization of new strains in broiler flocks with poor performance

Chicken astroviruses (CAstV) were associated with retarded growth, enteritis, kidney diseases, and white chick syndrome. In the current study, we aimed to evaluate the effect of CAstV infection on growth, performance, and gross and histopathological picture of commercial chicken flocks suffering increased culling rate and decreased performance. Samples were collected for virus isolation, identification, and sequencing on day one, 15 days, and 30 days of age. Body weight, feed conversion rate, and mortality rates were determined. A gross examination was performed, and tissue samples from the liver, intestine, kidneys, heart, and lungs were kept in formalin for histopathological evaluation. Embryos inoculated with CAstV revealed dwarfism, and edema. The cytopathic effect on CAstV inoculated cells included aggregation,, and sloughing. The isolated Egyptian isolates shared the highest nucleotide homology (93%) with the Korean isolate Kr/ADL102655-1/2010 and showed the most distant relation to the Indian isolate Indovax/APF/1319 with 82–83% homology. Body weight exhibited significant reduction with a decrease in feed conversion rate in CAstV infected flocks. Gross examination of CAstV-infected chickens revealed white feathered chicks on day one, and poor body condition in older chickens as well as swollen kidneys. Histopathological examination of CAstV-infected birds showed mild proventriculitis, shortening of intestinal villi, enteritis, focal hepatocellular necrosis, pericarditis, myocarditis, and proliferative response in lung tissue. Kidneys showed interstitial nephritis, urate deposition, and glomerular hypercellularity. CAstV is a chicken pathogen that could be related to decreased performance, and screening of flocks for CAstV might be an essential step for breeders.

Molecular detection of chicken astrovirus in broiler chicken, Malaysia

The emergence of avian diseases can cause major economic problems due to production losses and mortality in domestic poultry. Astrovirus is frequently associated with enteric diseases in poultry, being isolated from cases of runting-stunting syndrome (RSS) of broiler chickens, poult enteritis complex (PEC), and poult enteritis mortality syndrome (PEMS) of turkeys. Avian astrovirus can be detected in chickens from both healthy and poorly performing flocks. In Malaysia, information and reports regarding chicken astrovirus (CAstV) in poultry are limited. The objective of this study is to perform a phylogenetic study on the avian astrovirus isolated from a suspected case in 2019 and to determine the subgroups of avian astrovirus strains that existed in Malaysia. Reverse Transcription Polymerase chain reaction (RT-PCR) was performed based on the partial ORF1b gene and the nucleotide sequence was analyzed. Phylogenetic analysis showed that this isolate was clustered together with CAstV strains from several strain from USA, Malaysia and others. Furthermore, the isolate from broiler chicken showed 97.2% to 99.4% of its nucleotide identity with isolates from the American strains, compared to the previously CAstv Malaysia strain, which shared 94.8% to 95%.Therefore, the current study provides important information on the epidemiology of CAstV and highlights the importance of control strategies against CAstV-infected poultry in Malaysia.

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

Simple SummaryEnteric 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.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 Review of the Emerging Poultry Visceral Gout Disease Linked to Avian Astrovirus Infection.

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

Genetic diversity and pathogenicity of novel chicken astrovirus in China

ABSTRACT Five 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 in specific pathogen-free (SPF) chicken embryos and chickens. The complete genomes of the five 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, all belonging to different subgroups was studied. The results showed that the mortality of the chicken embryos was 100% when infected with any strain at a dose of more than 103 TCID50, 35% in SPF chickens infected with strain WSC, 25% with MHC and 15% with MHW. The body weights of chickens 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 types 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.

Pathogenesis of Chicken Astrovirus Related Illnesses.

Of the several known viruses, chicken astrovirus (CAstV) has been associated with diarrhea, runting-stunting syndrome, severe kidney disease, and gout, and white chick syndrome (WCS) in young broiler chicks. Discovered in 2004, CAstV consists of two genogroups with an expanding subgroup because of the diversity exhibited in its viral capsid sequence. Despite these findings, there exists a dearth of knowledge on its pathogenesis. This review highlights the pathogenesis and development of in vivo and in vitro models.

Detection and molecular phylogenetic analysis of chicken astrovirus in Saga prefecture, Japan.

We detected three chicken astrovirus strains in 4-day-old broiler chickens with high mortality and visceral gout and one strain from 150-day-old hens without clinical symptoms in Saga prefecture, Japan. Phylogenetic analysis based on ORF2 amino acid sequences revealed that the strains from the visceral gout cases belonged to subgroup Bi, and the strain from hens without clinical symptoms belonged to subgroup Aiii. Our study showed that CAstV had infiltrated into Saga prefecture, Japan. This is the first report of CAstV in Japan.

An Insight into the Molecular Characteristics and Associated Pathology of Chicken Astroviruses.

The chicken astrovirus (CAstV) is a ubiquitous enteric RNA virus that has been associated mainly with conditions, such as the runting-stunting syndrome, severe kidney disease, visceral gout, and white chick syndrome, in broiler-type chickens worldwide. Sequence analysis of the capsid genes’ amino acids of the strains involved in these conditions reveals a genetic relationship and diversity between and within the CAstV genogroups and subgroups based on phylogenetic analysis, genetic distance (p-dist), and pathogenicity. While the two genogroups (A and B) are demarcated phylogenetically, their pairwise amino acid sequence identity is 39% to 42% at a p-dist of 0.59 to 0.62. Group-A consists of three subgroups (Ai, Aii, and Aiii) with an inter- and intra-subgroup amino acid identity of 78% to 82% and 92% to 100%, respectively, and a p-dist of 0.18 to 0.22. On the other hand, the six subgroups (Bi, Bii, Biii, Biv, Bv, and Bvi) in Group-B, with a p-dist of 0.07 to 0.18, have an inter- and intra-subgroup amino acid identity of 82% to 93% and 93% to 100%, respectively. However, these groupings have little to no effect on determining the type of CAstV-associated pathology in chickens.

Molecular Detection, Characterisation and Serological Survey of Chicken Astrovirus from Broiler Flocks in Malaysia

Astroviruses have been associated with enteric and extra-intestinal disorders in many animal species, including chickens. Here, we describe the detection and characterisation of chicken astrovirus (CAstV) in broilers and its seroprevalence in broiler breeder flocks. Based on PCR protocol, viral confirmation was carried out on clinical tissue samples from broiler chickens suffering from uneven growth and poor performance. The tissues were molecularly detected for CAstV with differential diagnostic testing against the Newcastle disease virus, infectious bronchitis virus, avian nephritis virus, avian rotavirus, fowl adenovirus and avian reovirus. Polymerase gene-based phylogenetic analyses of the twenty samples detected positive for CAstV indicate they belong to Group I and are related to strains from the US, UK, India and Poland. From these 20 samples, CastV could be isolated from 3 samples upon inoculation in 5-day-old specific-pathogen-free (SPF) embryonated chicken eggs (ECE); virus-infected embryos showed dwarfing, haemorrhages, oedema and gelatinous lesions at harvest. The enzyme-linked immunosorbent assay (ELISA) results revealed a high prevalence of antibodies against CAstV amongst the broiler breeder flocks tested. It is the first study that describes the detection and prevalence of CAstV in broiler chickens and broiler breeder flocks in Malaysia.

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.

Isolation, Identification, and Genomic Characterization of Chicken Astrovirus Isolates From China.

Chicken astrovirus (CAstV) infection can cause diarrhea, nephritis, stunted growth, and “white chickens” condition, resulting in economic losses to the poultry industry. Currently, a few CAstVs were isolated and a few full-length genome sequences of CAstV have been deposited in the GenBank. In the present study, two CAstV isolates (AAstV/Chicken/CHN/2017/NJ01 and AAstV/Chicken/CHN/2018/CZ01) were successfully isolated by using LMH cells, and we molecularly characterized these two CAstV isolates and observed the effect of these two isolates on hatchability using chicken embryo infection experiment. The genetic analysis demonstrated that these two strains had the typical characteristics of avian astroviruses, which were composed of three open reading frames, 5′UTR, and 3′UTR. The full-length genome sequence showed a high-degree identity at nucleotide level of 97.5–98.7% among Chinese isolates suggesting their common ancestors and limited sequence divergence. Sequence analysis of ORF2, which encodes the capsid protein associated with classification of avian astrovirus, revealed our two isolates belonging to CAstV Bi subtype. At the amino acid level, the complete capsid region of Chinese strains shared genetic distances of 0.03–0.04 with FP3 strains isolated from the UK, suggesting their common origin. Meanwhile, hatchability reduction was observed. These results provided novel insights into the molecular epidemiology and hatchability effect of CAstV.

A Review of the Emerging White Chick Hatchery Disease.

White chick hatchery disease is an emerging disease of broiler chicks with which the virus, chicken astrovirus, has been associated. Adult birds typically show no obvious clinical signs of infection, although some broiler breeder flocks have experienced slight egg drops. Substantial decreases in hatching are experienced over a two-week period, with an increase in mid-to-late embryo deaths, chicks too weak to hatch and pale, runted chicks with high mortality. Chicken astrovirus is an enteric virus, and strains are typically transmitted horizontally within flocks via the faecal–oral route; however, dead-in-shell embryos and weak, pale hatchlings indicate vertical transmission of the strains associated with white chick hatchery disease. Hatch levels are typically restored after two weeks when seroconversion of the hens to chicken astrovirus has occurred. Currently, there are no commercial vaccines available for the virus; therefore, the only means of protection is by good levels of biosecurity. This review aims to outline the current understanding regarding white chick hatchery disease in broiler chick flocks suffering from severe early mortality and increased embryo death in countries worldwide.