Astrovirus-induced "white chicks" condition - field observation, virus detection and preliminary characterization

Detection and genetic characterization of chicken astrovirus and Avian Nephritis virus from hatchery to farm

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 hatching decrease mainly due to embryo deaths, pale and runted chicks too weak to hatch. Hatchery diseases occur through direct egg infection or through vertical transmission. However, the specific role of astroviruses in these diseases is still largely unknown. To elucidate this question, 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 was followed from the hatchery to the farm. The presence of both CAstV and ANV was monitored by evaluating the viral load, in environmental and animal samples. Interestingly, both viruses were detected in chick yolk sacs at 18th day incubation, in the gut contents of 1-day chicks, whereas the hatchery environmental samples, the external eggs' surfaces and the embryos intestinal contents were negative. The CAstV copy number was higher in animal tissues from hatchery, while a greater ANV load was detected in animal tissue from farm. Moreover, our data suggested a vertical transmission ascribed to both viruses. A frequent co-infection was also observed in samples from both hatchery and farm. Lastly, the first Italian full-length genome and molecular characterization of ANV was obtained.

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

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

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.

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.

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.

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.

Molecular characterization of chicken astrovirus from high embryonic mortality based on the capsid protein (ORF2) gene, in Brazil

ABSTRACTIn recent years, reports of chicken astrovirus (CAstV) infections in commercial birds have increased, affecting the poultry industries in Brazil and worldwide. The objective of this study was to use molecular methods to characterize the CAstV found in one breeding and three different incubation companies that reported increased embryonic mortality and the appearance of birds with white chick syndrome (WCS). RT-qPCR with SyBR green chemistry were used to determine the presence of the virus in the feces of breeders, organs of newborn chickens, and unhatched embryos. By sequencing the ORF2 that codes for the viral capsid, the strains responsible for these clinical signs were characterized using strains previously reported in Brazil, North America, Europe, and Asia. The percentage of identity of the amino acid sequences compared with those from group A was less than 41% (37.01% to 40.52%) and the identity with those from subgroups Bi, Bii, and Biii was less than 90% (81.81% to 89.85%). Therefore, the sequences were characterized within subgroup Biv with identity greater than 95% (95.26% to 99.59%), together with CAstV strains previously found in Brazil, Canada, and the United States. Using antigenicity prediction tools, 14 highly conserved peptides located on the surface of the capsid protein were considered potentially responsible for inducing the immune response in the host. Our data provide important information related to the increase in embryo mortality in vertically infected birds, reinforcing the potential association of WCS with CAstV Biv subgroup.

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.

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.

First Isolation and Molecular Characterization of Chicken Astrovirus and Avian Nephritis Virus in Chickens in Bangladesh

Chicken astrovirus (CAstV) and avian nephritis virus (ANV) are enteric viruses of poultry and have infected a wide range of poultry species worldwide, causing runting-stunting syndrome (RSS), which requires virus screening and results in serious economic damage. No confirmed cases have been reported from Bangladesh. In the present study, CAstV and ANV were monitored in Bangladesh. We monitored samples for CAstV and ANV and compared their genomic sequences to other reference strains. We found 8/31 flocks (25.8%) were positive for CAstV, 6/31 flocks (19.3%) had mixed infection of CAstV and ANV, and 1 flock (3.2%) was positive for ANV. Only ANV and a combination of CAstV and ANV were found in broilers and broiler breeders, but CAstV was found in all types of chickens. We isolated two of each from CAstV and ANV through specific pathogen-free chicken embryonated eggs via the yolk sac route. Phylogenetic analysis based on the ORF1b conserved region of CAstV and ANV suggested that the locally circulating strain was closely related to the strains isolated from India and Brazil. This report is the first molecular characterization of CAstV and ANV in Bangladesh. This study highlights that CAstV and ANV are circulating in Bangladeshi poultry.

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.

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.

Transcriptome Sequencing of the Spleen Reveals Antiviral Response Genes in Chickens Infected with CAstV

Astrovirus infections pose a significant problem in the poultry industry, leading to multiple adverse effects such as a decreased egg production, breeding disorders, poor weight gain, and even increased mortality. The commonly observed chicken astrovirus (CAstV) was recently reported to be responsible for the "white chicks syndrome" associated with an increased embryo/chick mortality. CAstV-mediated pathogenesis in chickens occurs due to complex interactions between the infectious pathogen and the immune system. Many aspects of CAstV-chicken interactions remain unclear, and there is no information available regarding possible changes in gene expression in the chicken spleen in response to CAstV infection. We aim to investigate changes in gene expression triggered by CAstV infection. Ten 21-day-old SPF White Leghorn chickens were divided into two groups of five birds each. One group was inoculated with CAstV, and the other used as the negative control. At 4 days post infection, spleen samples were collected and immediately frozen at -70 °C for RNA isolation. We analyzed the isolated RNA, using RNA-seq to generate transcriptional profiles of the chickens' spleens and identify differentially expressed genes (DEGs). The RNA-seq findings were verified by quantitative reverse-transcription PCR (qRT-PCR). A total of 31,959 genes was identified in response to CAstV infection. Eventually, 45 DEGs (p-value < 0.05; log2 fold change > 1) were recognized in the spleen after CAstV infection (26 upregulated DEGs and 19 downregulated DEGs). qRT-PCR performed on four genes (IFIT5, OASL, RASD1, and DDX60) confirmed the RNA-seq results. The most differentially expressed genes encode putative IFN-induced CAstV restriction factors. Most DEGs were associated with the RIG-I-like signaling pathway or more generally with an innate antiviral response (upregulated: BLEC3, CMPK2, IFIT5, OASL, DDX60, and IFI6; downregulated: SPIK5, SELENOP, HSPA2, TMEM158, RASD1, and YWHAB). The study provides a global analysis of host transcriptional changes that occur during CAstV infection in vivo and proves that, in the spleen, CAstV infection in chickens predominantly affects the cell cycle and immune signaling.

Molecular characterisation and pathogenicity of novel Malaysian chicken astrovirus isolates

ABSTRACTChicken astrovirus (CAstV) has for over a decade been associated with runting stunting syndrome (RSS), severe kidney disease and visceral gout, and white chick syndrome (WCS). However, molecular characteristics and pathogenicity of the virus in day-old specific pathogen-free (SPF) chicks is scarce. This study focused on the characterisation of near-complete genome of three Malaysian CAstV isolates following virus propagation in specific-pathogen-free (SPF) embryonated chicken eggs (ECE) and pathogenicity in day-old SPF chicks. The three isolates demonstrated unique features including a point mutation in their intergenic regions and an additional stem-loop II-like motif (s2 m) in ORF-2. Pairwise sequence comparison and phylogenetic analysis of the ORF-2 amino acid of the three isolates revealed an identity share of 86 to 91% with group B CAstVs while forming a new subgroup in addition to the known four subgroups (Bi, Bii, Biii and Biv) that exhibit high identity of between 95 to 100% within the subgroups. In the pathogenicity study, birds in the infected and exposed sentinel groups exhibited lethargy and diarrhoea 3 days post-inoculation (dpi) that declined by 6 dpi and 20% growth retardation by 9 dpi. Mild lymphocytic aggregates in the duodenum, tubular degeneration and interstitial nephritis were observed in the intestines and kidneys, respectively, in both groups. In addition, the mean virus copy number of the cloacal swabs were log₁₀ 13.23 at 3 dpi and log₁₀ 9.04 at 6 dpi for the infected and exposed sentinels, respectively. The study suggests that the Malaysian isolates should be assigned to a new subgroup, Bv within group B CAstV.

Isolation and characterization of a novel chicken astrovirus in China

Chicken astrovirus (CAstV) is associated with kidney disease and visceral gout, runting and stunting syndrome, and white chick hatchery disease, causing economic losses to the poultry industry worldwide. In this study, 55.6% of 36 clinical samples from Guangdong province in China were positive for CAstV, but negative for other common enteric viruses, including avian nephritis virus, infectious bronchitis virus, fowl adenovirus Group I, Newcastle disease virus, chicken parvovirus, reovirus, and rotavirus by PCRs and RT-PCRs. A CAstV strain, named GD202013, was isolated from Guangdong province in south China, and was identified by CAstV RT-PCR. A whole genome sequence analysis demonstrated that GD202013 shares 76.0 to 88.1% identity with 24 reference strains in GenBank. Phylogenetic analysis, based on whole genome and capsid protein, showed that GD202013 is more closely related to 2 US strains (GA2011/US/2011 and 4175/US/2011) belonging to subgroup Bii. Recombination analysis indicated that GD202013 is a recombinant strain formed by 3 strains: a major parent strain CkP5/US/2016, and 2 minor parent strains (GA2011/US/2011 and G059/PL/2014). In addition, the chicken embryo infection experiment demonstrated that GD202013 causes hatchability reduction, growth depression, and death of embryos. Macroscopic and microscopic lesions in the liver, kidney and small intestine were observed in the dead-in-shell embryos. This is the first report of the novel CAstV infection in China.

Detection and characterization of chicken astrovirus associated with hatchery disease in commercial day-old turkeys in southwestern Nigeria

Infectious diseases are a major obstacle to profitable poultry production in Nigeria due to the mortality and severe economic losses they cause. In particular, they are a potent threat to attainment of the food security goals of government and national self-sufficiency in food production. Thus, there is a need for continuous monitoring of the nation’s poultry population for these diseases. As part of an ongoing investigation of enteric viruses associated with poor performance or hatchery diseases in commercial poultry in southwestern Nigeria, intestinal contents from 97 condemned or runted day-old commercial turkey poults were examined for turkey astroviruses, infectious bronchitis virus, chicken astrovirus (CAstV), avian nephritis virus, avian rotavirus, avian reovirus, fowl adenovirus, and chicken parvovirus by virus isolation, electron microscopy (EM), polymerase chain reaction (PCR), and reverse transcription PCR. The samples were collected from five commercial hatcheries and five farms located in southwestern Nigeria. While all samples tested negative for other viruses, CAstV was detected in the majority (83.5%) of the birds, although some pleomorphic virus-like particles with surface projections that appeared fringed or fimbriated were observed in five of the cell culture samples by EM. Phylogenetic analysis revealed these CAstV strains belonged to the Bi clade. These findings not only implicate CAstV as the major cause of hatchery condemnations in commercial turkeys in southwestern Nigeria but also highlight the need for experimental studies to further establish its role in this disease condition.

A case of clubbed down syndrome in broilers

This study presents a case of clubbed down syndrome in conventional broilers. During the first week of life, severe growth retardation was observed in approximately 25% of the flock. The growth-retarded chicks weighed only 45 g and showed a typical feather disorder which was most apparent on their abdomen and was defined in literature as typical for clubbed down syndrome. Necropsies, histology, biochemical analysis of blood and liver samples, serology and different PCR tests were performed in broilers to assess the aetiology of the clinical signs that were present in the affected broiler farm. Because of the suspicion of a possible link with the broiler-breeder farms, different investigations including serology, PCR and feed analysis were also performed on these farms. The results suggest that an accidentally excessive amount of calcium and iron in the feed of broiler-breeders, 3 weeks prior to first clinical signs in broilers, led to the development of clubbed down in the offspring, because of a relative Zn-deficiency in broiler-breeders and an absolute Zn-deficiency in the hatching eggs that were produced during this period. This appeared to be a reversible process as no clinical signs were observed in younger offspring of these broiler-breeders after they had consumed more of the new batch of feed. A potential involvement of Astrovirus could not be completely ruled out. This study demonstrates the importance of correct mineral concentrations in broiler-breeder feed and the impact it can have on the development of the offspring.

Chicken Astrovirus (CAstV) Molecular Studies Reveal Evidence of Multiple Past Recombination Events in Sequences Originated from Clinical Samples of White Chick Syndrome (WCS) in Western Canada

In this study, we aimed to molecularly characterize 14 whole genome sequences of chicken astrovirus (CAstV) isolated from samples obtained from white chick syndrome (WCS) outbreaks in Western Canada during the period of 2014–2019. Genome sequence comparisons showed all these sequences correspond to the novel Biv group from which no confirmed representatives were published in GenBank. Molecular recombination analyses using recombination detection software (i.e., RDP5 and SimPlot) and phylogenetic analyses suggest multiple past recombination events in open reading frame (ORF)1a, ORF1b, and ORF2. Our findings suggest that recombination events and the accumulation of point mutations may have contributed to the substantial genetic variation observed in CAstV and evidenced by the current seven antigenic sub-clusters hitherto described. This is the first paper that describes recombination events in CAstV following analysis of complete CAstV sequences originated in Canada.

Molecular Characterization and Determination of Relative Cytokine Expression in Naturally Infected Day-Old Chicks with Chicken Astrovirus Associated to White Chick Syndrome

White chick syndrome (WCS) is an emergent disease that affects hatchability and hatched chicks, resulting in high mortality and economic losses, and is related to chicken astrovirus (CAstV). This syndrome has been reported in several countries worldwide, and groups A iii and B vi of CAstV have been determined; however, in Brazil, the virus has not been genotyped. The innate immunity of chicks affected by WCS or any CAstV is poorly understood and studied, and it is important to determine whether relative cytokine expression occurs during the early stages of the life of chicks. The aim of the present investigation is to detect and molecularly characterize CAstV associated with WCS, examine the macroscopic and microscopic lesions in the jejunum and spleen, and determine cytokine expression in the jejunum, liver, spleen and thymus of chicks naturally infected with WCS. To do so, we applied a pathological and molecular approach for CAstV detection and characterization, as well as the quantification of the relative mRNA expression of several cytokine genes. The phylogenetic analyses of the sequences obtained herein classified CAstV as uniquely belonging to group B iv, showing a high similarity of nucleotides (NT) (75.7-80.6%) and amino acids (AA) (84.2-89.9%) with the members of group B and a low similarity of NT (46.7-47.9%) and AA (37.8-38.9%) with the virus belonging in group A. CAstV was also detected and quantified in the serum, spleen, thymus and jejunum, the latter being the organ where CAstV had the highest viral concentration. However, this organ did not present any microscopical alterations. In contrast, we observed necrotic hepatitis in the liver of the affected subjects. On the other hand, we observed the activation of several T helper 1 (Th1)- and T helper 2 (Th2)-cytokines (IFN-γ, IL-2, IL-8, IL-12p40, IL-15, TGF-β4, TNF-SF-15 and t-BET), without being able to control the viral replication due to the high concentration of viral particles in some organs, principally in the gut. One possible role of these cytokines is contributing to the control of inflammation and cell protection of intestinal cells, principally during the early activation of immune responses. However, the fact that these responses are not mature enough to control the viral infection means that more studies need to be carried out to elucidate this topic.

A Cross Sectional Survey of Chicken Astroviruses Antibody in Broiler and Sonali (Cross-Bred) Chickens in Selected Areas in Bangladesh

Chicken astroviruses (CAstV) are enteric viruses of poultry causing gastroenteritis, malabsorption, gout and white chick disease commonly known as runting-stunting syndrome (RSS). It can affect the wide range of poultry birds, especially chicken, turkey and duck worldwide. To our best knowledge there is no published report on presence of antibodies against CAstV in Bangladesh. Therefore, the study aimed to detect the presence of CAstV antibodies in broilers and sonali chickens (a cross-bread) in Bangladesh through a cross-sectional survey. A total of 454 blood samples from 66 flocks of broiler (n=343) and sonali chickens (n=111) of different ages were obtained during 2017 from four districts. The birds were healthy but were not vaccinated against CAstV. The samples were tested for specific antibodies against CAstV Group B by using commercially available ELISA kit. Overall, 16.74% (76/454) samples and 34.84% (23/66) flocks were positive for CAstV antibodies. The seroprevalence of CAstV was significantly (p=0.001) higher in sonali chickens (36.96%) than broiler (10.20%), while it was significantly higher (p=0.001) in birds of Bogura district (36.94%) than the other three districts. Regarding the age groups, seroprevalence was insignificantly (p=0.192) higher in sonali chicken before laying age (45%) than during laying age (27.45%). Regarding the seasons, CAstV infection was prevalent significantly (p=0.001) higher in winter season. Thus, the present study indicated the presence of CAstV in poultry in Bangladesh, so further studies are required to find out the magnitude of the problem in the country.

Molecular characterization of chicken astroviruses in gout-affected commercial broiler chickens in Haryana, India

Chicken astroviruses (CAstVs) infect young chicks and are associated with gastroenteritis, stunted growth or visceral gout (gout). True incidence and distribution of CAstVs as well as virus variants circulating in India is not well understood. In this study, 80 gout-affected broiler chicken flocks from Haryana, a north-western state of India, were tested for the presence of astroviruses by targeting the polymerase gene of both CAstV and avian nephritis virus (ANV) and capsid gene of CAstV. Of these, 22 (27.5%) flocks were found positive for CAstV, 7(8.75%) for ANV and 2 (2.5%) for both CAstV and ANV genome by reverse-transcription-polymerase chain reaction. CAstV was isolated by inoculating tissue (kidney) homogenate from gout-affected birds into specific-pathogen free embryonated chicken eggs where the infected embryos showed stunted growth with necrosis of liver and enlarged kidney with urate deposits. Capsid gene-based phylogenetic analysis revealed the clustering of CAstV strains from this study with Indian strains of serogroup Biii suggesting their antigenic relatedness. Thus the present study reveals the presence of chicken astroviruses in broiler chickens affected with gout.

White Chick Syndrome Associated with Chicken Astrovirus in Ontario, Canada

Sixty-four cases of white chick syndrome (WCS) in broiler breeders producing affected progeny were reported from seven hatcheries in Ontario, Canada, between 2009 and 2016, with 43 of those originating from two hatcheries owned by a single company. WCS cases were identified by the presence of typical chicks in the hatchery that were generally weak with pale to white down, enlarged abdomens, and occasionally brown wiry fluff on the dorsum of the neck. Affected embryos and chicks had characteristic gross and histologic liver lesions, and livers were positive for chicken astrovirus (CAstV) RNA by real-time reverse transcriptase PCR. Affected broiler breeder flocks experienced egg production drops of 0% to 21% and hatchability drops of 0% to 68.4%. The amino acid sequence of the region encoding the capsid gene of WCS viruses demonstrated all Ontario CAstV to be in Group B, Subgroup Bii.

Investigation of Enteric Viruses Associated With Runting and Stunting in Day-Old Chicks and Older Broilers in Southwest Nigeria

Enteric viruses are known to have significant economic impact on poultry, especially broiler chicken flocks, because of production losses attributable to poor feed conversion and weight gain. To sustain the Nigerian poultry industry that contributes significantly to the livestock sector of the economy, there is a need to investigate commercial broiler flocks in the country for the presence of enteric viruses causing runting and stunting, growth retardation, and hatchery diseases. Gut contents were collected from 158 day-old and six 14-week old runted/stunted broiler chickens in commercial farms (ten) and hatcheries (six) located in Southwest Nigeria. The samples were examined for the presence of chicken astrovirus (CAstV), avian nephritis virus (ANV), avian rotavirus (AvRV), chicken parvovirus (ChPV), and turkey astroviruses (TAstV-1 and−2) by polymerase chain reaction (PCR) and reverse transcriptase-PCR (RT-PCR) whereas avian reovirus (ARV) and fowl adenovirus (FAdV) by virus isolation (VI), RT-PCR, and PCR. While CAstV was detected in all the birds (100%), sporadic detection of ANV (5%), and ChPV (5%) was observed in day-old and/or older birds. Four isolates were obtained by VI with one isolate being ARV positive and other three FAdV positive by RT-PCR and PCR, respectively. These findings strongly suggest CAstV as a major cause of runting and stunting as well as hatchery condemnations in commercial broilers in Southwest Nigeria, although co-infections with ANV, FAdV, ARV, and ChPV cannot be ruled out. In addition, the possible vertical and horizontal transmissions of these viruses are discussed.

Discovery of novel astrovirus and calicivirus identified in ruddy turnstones in Brazil

Birds are the natural reservoir of viruses with zoonotic potential, as well as contributing to the evolution, emergence, and dissemination of novel viruses. In this study, we applied a high-throughput screening approach to identify the diversity of viruses in 118 samples of birds captured between October 2006 to October 2010 in the North and Northeast regions of Brazil. We found nearly complete genomes of novel species of astrovirus and calicivirus in cloacal swabs of ruddy turnstones (Arenaria interpres) collected in Coroa do Avião islet, Pernambuco State. These viruses are positive-sense single-stranded RNA with a genome of ~7 to 8 kb, and were designated as Ruddy turnstone astrovirus (RtAstV) and Ruddy turnstone calicivirus (RTCV), respectively. Phylogenetic analysis showed that RtAstV and RTCV grouped in a monophyletic clade with viruses identified from poultry samples (i.e., chicken, goose, and turkey), including viruses associated with acute nephritis in chickens. Attempts of viral propagation in monkey and chicken cell lines for both viruses were unsuccessful. Also, we found genomes related with viral families that infect invertebrates and plants, suggesting that they might be ingested in the birds’ diet. In sum, these findings shed new light on the diversity of viruses in migratory birds with the notable characterization of a novel astrovirus and calicivirus.

Economic Impacts of White Chick Syndrome in Ontario, Canada

A cluster of 12 cases of White Chick Syndrome (WCS) in broiler breeder flocks producing affected progeny occurred from June to November 2015 in two broiler chicken hatcheries owned by a single company in Ontario, Canada. Cases were identified by the presence of typical chicks in the hatchery characterized by pale to white down, enlarged abdomens, and occasionally brown wiry fluff on the dorsum of the neck that were generally weak. Affected broiler breeder flocks experienced egg production drops of 0% to 15% and hatchability drops of 1.8% to 49.1%. Some flocks experienced increased feed clean-up duration and/or reduced hatching egg weight. The financial impacts of WCS to affected hatching egg producers averaged $5,912 CAD (US$4,417) per 10 000 hens and were as great as $16,788 CAD (US$12,544) per 10 000 hens. The financial impacts of WCS to the affected hatcheries averaged $1,723 CAD (US$1,287) per 10 000 broiler breeder hens and were as great as $4,096 (US$3,060) per 10 000 hens.

Novel viruses in birds: Flying through the roof or is a cage needed?

Emerging viral diseases continue to have a major global impact on human beings and animals. To be able to take adequate measures in case of an outbreak of an emerging disease, rapid detection of the causative agent is a crucial first step. In this review, various aspects of virus discovery are discussed, with a special focus on recently discovered viruses in birds. Novel viruses with a potential major impact have been discovered in domestic and wild bird species in recent years using various virus discovery methods. Only a few studies report the detection of novel viruses in endangered bird species, although increased knowledge about viruses circulating in these species is important. Additional studies focusing on the exact role of a novel virus in disease and on the impact of a novel virus on bird populations are often lacking. Intensive collaboration between different disciplines is needed to obtain useful information about the role of these novel viruses.

Astrovirus Biology and Pathogenesis

Astroviruses are nonenveloped, positive-sense single-stranded RNA viruses that cause gastrointestinal illness. Although a leading cause of pediatric diarrhea, human astroviruses are among the least characterized enteric RNA viruses. However, by using in vitro methods and animal models to characterize virus-host interactions, researchers have discovered several important properties of astroviruses, including the ability of the astrovirus capsid to act as an enterotoxin, disrupting the gut epithelial barrier. Improved animal models are needed to study this phenomenon, along with the pathogenesis of astroviruses, particularly in those strains that can cause extraintestinal disease. Much like for other enteric viruses, the current dogma states that astroviruses infect in a species-specific manner; however, this assumption is being challenged by growing evidence that these viruses have potential to cross species barriers. This review summarizes these remarkable facets of astrovirus biology, highlighting critical steps toward increasing our understanding of this unique enteric pathogen.

Seroprevalence of antibodies to astrovirus in chickens in Grenada, West Indies

Aim:

Chicken astroviruses (CAstV) are known to cause mild gastroenteritis, growth depression, and even mortality in poultry, especially in chickens, turkeys, and ducks. To the best our knowledge, there is no published information on CAstV in Grenada. This study was conducted to determine the prevalence of astrovirus in chickens in Grenada.

Materials and Methods:

Blood samples from 366 indigenous chickens and 92 commercial chicken layers were collected from all parishes of the island and tested for antibodies against CAstV using commercial enzyme-linked immunosorbent assay.

Results:

The seroprevalence of antibodies against astrovirus was 57.6% (95%, Confidence interval [CI]: 47.4-67.2) in commercial layers and 61.5% (95%, CI: 56.4-66.3) in indigenous chickens. The results show the presence of infection throughout the island.

Conclusion:

The results show the infection with CAstV in approximately half of the chicken population in Grenada. This is the first report on the prevalence of CAstV in chickens in Grenada and the Caribbean region.

The first serological investigation of Chicken astrovirus infection in China

Chicken astrovirus (CAstV) is associated with 'white chick' syndrome, which increases embryo mortality and reduces hatchability in chickens. In the present study, 1760 sera were collected from 21 provinces in China to detect antibodies directed against CAstV with an ELISA. The sera were from different varieties of chicken in 85 flocks and all the flocks produced positive reactions. The overall seroprevalence in the birds tested was 60.68%. The prevalence increased from 34.17% to 74.44% with the increase of age. The positivity rates in layer flocks, layer parent flocks, broiler flocks, broiler parent flocks, and domestic chicken flocks were 70.17%, 89.00%, 31.67%, 59.05%, and 45.79%, respectively. These data indicate that CAstV infections are very common in China. This is the first report of the seroprevalence of CAstV infections in China.

A Review of the Strain Diversity and Pathogenesis of Chicken Astrovirus

Although a relatively recently emerged virus, identified only in 2004 as a separate species of avian astrovirus, chicken astrovirus (CAstV) has been associated with poor growth of broiler flocks, enteritis and diarrhea and is a candidate pathogen in cases of runting stunting syndrome. More recently CAstV has been implicated in cases of two other diseases of broilers as the sole etiological agent, namely severe kidney disease of young broilers with visceral gout and the “White Chicks” hatchery disease. Examination of the strains of CAstV associated with the two latter diseases reveals they are closely related genetically. This review will discuss the pathogenesis of CAstV in relation to strain diversity and the effects of vertical versus horizontal transmission, virus load, co-infections and age of bird at infection, all factors that may impact upon disease severity.

Astrovirus Pathogenesis

Astroviruses are a major cause of diarrhea in the young, elderly, and the immunocompromised. Since the discovery of human astrovirus type 1 (HAstV-1) in 1975, the family Astroviridae has expanded to include two more human clades and numerous mammalian and avian-specific genotypes. Despite this, there is still little known about pathogenesis. The following review highlights the current knowledge of astrovirus pathogenesis, and outlines the critical steps needed to further astrovirus research, including the development of animal models of cell culture systems.

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.

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.