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 a virulent goose astrovirus genotype-2 with high mortality in vitro and in vivo.

Goose astrovirus (GAstV) is a newly identified viral pathogen threatening waterfowl, exhibiting a high prevalence across various regions in China. Notably, the Guanghan District of Deyang City, situated in Sichuan Province, has faced a outbreak of GAstV, resulting in significant mortality among goslings due to the induction of gout-like symptoms. In our research, we successfully isolated a GAstV strain known as GAstV SCG3. This strain exhibits efficient replication capabilities, proving virulent in goslings and goose embryos. Our study delved into the characteristics of GAstV SCG3 both in vitro and in vivo. Additionally, we examined tissue phagocytosis and the distribution of GAstV SCG3 in deceased goslings using H&E staining and IHC techniques. According to the classification established by the ICTV, GAstV SCG3 falls under the category of GAstV genotype-2. Notably, it demonstrates the highest homology with the published AHAU5 sequences, reaching an impressive 98%. Furthermore, our findings revealed that GAstV SCG3 exhibits efficient proliferation exclusively in goose embryos and in LMH cells, while not manifesting in seven other types of avian and mammalian cells. Significantly, the mortality of GAstV on goslings and goose embryos are 93.1 and 80%, respectively. Moreover, the viral load in the livers of infected goslings surpasses that in the kidneys when compared with the attenuated strain GAstV SCG2. The mortality of GAstV is usually between 20% and 50%, our study marks the first report of a virulent GAstV strain with such a high mortality.

Molecular characterization and pathogenicity of novel Malaysian chicken astrovirus isolates.

ABSTRACTChicken astrovirus (CAstV) has for over a decade been associated with runting stunting syndrome, severe kidney disease and visceral gout, and white chick syndrome. However, knowledge of the molecular characteristics and pathogenicity of the virus in day-old specific pathogen-free (SPF) chicks is scarce. This study focused on the characterization of near-complete genome of three Malaysian CAstV isolates following virus propagation in SPF embryonated chicken eggs 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 (s2m) in ORF-2. Pairwise sequence comparison and phylogenetic analysis of the ORF-2 amino acid sequence of the three isolates revealed an identity share of 86-91% 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% and 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 numbers 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. RESEARCH HIGHLIGHTSA single run of NGS protocol is capable of generating a near-complete genome sequence of CAstV.The Malaysian CAstV isolates cluster together and exhibit 86-91% identity with published group B CAstVs.The Malaysian CAstVs encode an additional stem-loop II-like motif (s2m) in ORF-2.The isolates are pathogenic to day-old SPF chicks with lesions mainly in the intestine and kidneys.

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.

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

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

Pathogenicity of novel goose-origin astrovirus causing gout in goslings.

BACKGROUND: A novel goose-origin astrovirus (GoAstV) has broken out across China in recent years, causing gout in goslings with a mortality rate of around 50%. However, our understanding of the dynamic distribution, tissue tropism and pathogenesis of GoAstV is incomplete. In order to assess its pathogenicity, one-day-old goslings were inoculated separately with GoAstV via oral and subcutaneous injection routes. RESULTS: Clinical symptoms, gross and microscopic lesions, blood biochemical parameters and viral loads were detected and recorded for 20 days after infection. Typical gout was observed in experimental goslings. GoAstV can be replicated in tissues and cause pathological damage, especially in the kidney, liver, heart and spleen. Virus-specific genomic RNA was detected in blood, cloacal swabs and all representative tissues, and virus shedding was detected up to 20 days after inoculation, suggesting that GoAstV has a wide tissue tropism and spread systematically after inoculation. The viral copy numbers examined in kidney were the highest, followed by spleen and liver. CONCLUSION: This experiment determined the accurate value of viral loads and biochemical indicators of GoAstV-induced goslings. These findings increase our understanding of the pathogenicity of GoAstV in goslings and provide more reference for future research.

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

In 2019, a new type of infectious disease characterized with haemorrhage and swellings of kidneys, occurred on commercial duck farms in Shandong province, China. Our systematic investigation led to the isolation of an astrovirus, designated AstV-SDTA strain and was isolated from a diseased duckling using LMH cells. Similar clinical symptoms were reproduced by experimental infection using the AstV-SDTA strain. The complete genome sequencing characterization of AstV-SDTA was conducted using next-generation sequencing (NGS) technique on Illumina HiSeq platform, and used polymerase chain reaction method to verify the NGS results for the obtained whole sequences. Phylogenetic analysis revealed that AstV-SDTA strain belongs to a novel goose astrovirus (GoAstV) branch of avian astroviruses, and the nucleotide homology based on the complete genome sequences among AstV-SDTA and other GoAstV strains deposited in Genbank was 97.2-98.8%. Taken together, these results suggest that the cross-species transmission of novel GoAstV between domestic waterfowl is possible. Further surveillance of novel GoAstV in poultry are needed in order to gain a better understanding of both the molecular and evolutionary characteristics of novel GoAstV.

First report of a novel goose astrovirus outbreak in Cherry Valley ducklings in China.

A highly acute disease broke out in ducklings in Shandong Province in March 2019. The disease was characterized as visceral gout, with a mortality rate of 30%. The causative agent, which has given rise to similar symptoms in goslings, has been confirmed to be a novel goose astrovirus. The novel goose astrovirus, which was designated as the SDXT strain, was identified from a diseased duck farm using duck embryo primary cells in an experimental infection test. Genomic sequence analysis, as well as phylogenetic analysis of the viral proteins, revealed that the SDXT strain was closely related to a novel goose astrovirus of the Avastrovirus three species. These results indicate that the novel goose astrovirus may cross-host infect ducklings. Further studies are needed to define its host range and transmission route.

Isolation and characterization of an astrovirus causing fatal visceral gout in domestic goslings.

Astroviruses are recognized as a leading cause of gastroenteritis in humans and animals. They are also associated with extra-intestinal diseases, such as hepatitis in ducklings, nephritis in chickens, and encephalitis in cattle. In February 2017, a fatal infection of goslings characterized by visceral urate deposition was reported in the Shandong province, China. Our systematic investigation led to the isolation of an astrovirus, designated AAstV/Goose/CHN/2017/SD01, and similar disease was reproduced by experimental infection of healthy goslings, fulfilling Koch's postulates. The isolated astrovirus replicated well and resulted in 100% mortality of goose embryos. Complete genome sequence analysis revealed that the isolate was genetically distinct from known astroviruses and closely related to members of the avastrovirus genogroup II. Experimental infection showed that the isolate was highly pathogenic in goslings, causing clinical signs, growth repression and in many cases mortality. Histopathological examination indicated that lesions occurred mainly in the kidneys of infected birds. However, virus-specific genomic RNA was detected in all representative tissues, and virus shedding was detected up to 12 days after inoculation, suggesting that the isolate was able to spread systemically and replicate efficiently in vivo. Collectively, our study demonstrates, for the first time, the etiological role of a genetically distinct astrovirus in the fatal infection of goslings.

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.

Oral Administration of Astrovirus Capsid Protein Is Sufficient To Induce Acute Diarrhea In Vivo.

The disease mechanisms associated with the onset of astrovirus diarrhea are unknown. Unlike other enteric virus infections, astrovirus infection is not associated with an inflammatory response or cellular damage. In vitro studies in differentiated Caco-2 cells demonstrated that human astrovirus serotype 1 (HAstV-1) capsid protein alone disrupts the actin cytoskeleton and tight junction complex, leading to increased epithelial barrier permeability. In this study, we show that oral administration of purified recombinant turkey astrovirus 2 (TAstV-2) capsid protein results in acute diarrhea in a dose- and time-dependent manner in turkey poults. Similarly to that induced by infectious virus, TAstV-2 capsid-induced diarrhea was independent of inflammation or histological changes but was associated with increased intestinal barrier permeability, as well as redistribution of sodium hydrogen exchanger 3 (NHE3) from the membrane to the cytoplasm of the intestinal epithelium. Unlike other viral enterotoxins that have been identified, astrovirus capsid induces diarrhea after oral administration, reproducing the natural route of infection and demonstrating that ingestion of intact noninfectious capsid protein may be sufficient to provoke acute diarrhea. Based on these data, we hypothesize that the astrovirus capsid acts like an enterotoxin and induces intestinal epithelial barrier dysfunction. IMPORTANCE: Acute gastroenteritis, with its sequela diarrhea, is one of the most important causes of childhood morbidity and mortality worldwide. A variety of infectious agents cause gastroenteritis, and in many cases, an enterotoxin produced by the agent is involved in disease manifestations. Although we commonly think of bacteria as a source of toxins, at least one enteric virus, rotavirus, produces a protein with enterotoxigenic activity during viral replication. In these studies, we demonstrate that oral administration of the turkey astrovirus 2 (TAstV-2) structural (capsid) protein induces acute diarrhea, increases barrier permeability, and causes relocalization of NHE3 in the small intestine, suggesting that rotavirus may not be alone in possessing enterotoxigenic activity.

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.

Age-Related Susceptibility of Turkeys to Enteric Viruses.

Several different enteric viruses have been identified as the causes of gastrointestinal infections in poultry. Enteric virus infections are well characterized in poults, but limited studies have been conducted in older birds. The susceptibility of 2-, 7-, 12-, 30-, and 52-wk-old turkeys to turkey coronavirus (TCoV) and turkey astrovirus (TAstV) was evaluated, as well as the effect of combined infection of TAstV and TCoV in 2-wk-old poults and turkey hens. From cloacal swabs and intestines, TCoV was consistently detected by reverse transcriptase-PCR throughout the experimental period (1-21 days postinoculation [DPI]) from all age groups. In contrast, the last detection point of TAstV gradually decreased to 21, 16, and 12 DPI in birds inoculated at 2, 7, and 12 wk of age, respectively, and viral RNA was rarely detected from cloacal swabs or intestinal contents in turkey hens within 3 DPI. Infection with TAstV alone did not affect body weight in poults or egg production in hens. The combined infection of TAstV and TCoV did not induce more severe clinical signs and pathology than the TCoV infection alone. However, a severe prolonged decrease in egg production (about 50%) was observed in turkey hens in the combined infection group compared with a transient egg production drop in the TCoV-infected hens alone. The underlying mechanism regarding the age-related TAstV susceptibility and the pathogenesis of the TAstV and TCoV coinfection in layer hens needs to be further elucidated.

Role of chicken astrovirus as a causative agent of gout in commercial broilers in India.

Several outbreaks of gout were reported in commercial broilers in India during 2011 and 2012, causing up to 40% mortality in the birds. Gross and histopathological observations confirmed gout. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis from kidney samples of gout-affected birds indicated the presence of chicken astrovirus (CAstV) in 41.7% of cases and a mixed infection of CAstV and avian nephritis virus (ANV) in 36.4% of cases. CAstV isolated from gout-affected kidneys by inoculating embryonated specific pathogen free (SPF) eggs showed dwarfing in embryos and a cytopathic effect in chicken embryo kidney cells. Inoculation of 1-day-old SPF and broiler chicks with CAstVs caused gout and mortality between 4 and 10 days post inoculation. Virus isolation and qRT-PCR analysis showed the presence of only CAstV in inoculated chicks. Sequence analysis of capsid genes indicated a major group of Indian CAstVs that displayed 92.0 to 99.2% intergroup amino acid identity and 83.9 to 90.4% identity with subgroup Bi CAstVs of UK origin. We designated this group Indian Bi. Analysis of the partial polymerase amino acid sequences of our isolates indicated two groups of CAstVs (Indian 1 and 2) that displayed 90.2 to 95.5% amino acid identity between them. We thus report for the first time that, in addition to infectious bronchitis virus and ANV, CAstVs are a causative agent of gout.

Experimental infection of poults and guinea fowl with genetically distinct avian astroviruses.

Avian astroviruses, of the genus Avastrovirus, are recognized as being the cause of enteritis in different bird species worldwide. In particular, turkeys are very susceptible and can be severely affected by this viral agent. More recently, astroviruses were detected in diseased guinea fowl in Italy but whether or not they were the causative agents of the clinical disease was not established. Despite the distribution and relevance of Avastrovirus infection, very little information on pathogenesis or factors influencing the pathogenicity of astroviruses is available. To increase available data on the pathogenesis of these viruses and to test the hypothesis of possible interspecies transmission, experimental infections were carried out in turkeys and guinea fowl with two genetically distinct avian astroviruses, namely TK-6363 and GF-5497, originating respectively from diseased turkey poults and guinea fowl. Data obtained in our study show that both of the viruses selected were able to infect young birds of the species in which they were originally detected. Additionally, these viruses were able to infect young birds of different species causing clinical signs, thus providing experimental evidence for the infection of distinct avian astroviruses in different avian species.

The role of type-2 turkey astrovirus in poult enteritis syndrome.

An experimental study was conducted to determine the comparative pathogenicity of type-2 turkey astrovirus (TAstV-2) obtained from turkey flocks afflicted with poult enteritis syndrome (PES) and from turkey flocks displaying no apparent signs of infection. In total, ninety 7-d-old poults, which tested negative for the presence of astrovirus, rotavirus, coronavirus, and reovirus by reverse transcriptase (RT) PCR , were divided evenly into 3 groups: A, B, and C. Birds in group A were inoculated orally with turkey astrovirus-positive intestinal contents from birds affected with PES. Group B received turkey astrovirus-containing intestinal contents from apparently healthy flocks. Group C served as a negative control and was given PBS. Clinical signs of diarrhea, depression, and dullness were observed in group A. Birds in group B also showed clinical signs similar to those in group A, although the signs were milder in nature. Birds in group C did not show any clinical signs. At 16 d postinoculation, the BW of birds in group A was significantly lower than that of birds in groups B or C. In addition, the bursa size was reduced in group A, but not in groups B or C. Birds in groups A and B, but not in group C, were found to shed turkey astrovirus in their feces, as detected by RT-PCR. These results provide a preliminary indication that TAstV-2 from PES birds may be more pathogenic than TAstV-2 from apparently healthy poults. Further studies are needed to determine if pathogenic and nonpathogenic strains of TAstV-2 exist in the environment. These results also reinforce our previous observations that astrovirus is involved in PES, causing significant retardation in growth and weight gain.

Detection and characterization of avian nephritis virus in ducklings.

The first evidence of avian nephritis virus (ANV) in ducks is described. A diagnostic investigation was performed on three duck farms in Croatia. Samples from dead-in-shell ducklings and ducklings aged 30 days were collected and prepared for molecular and histopathological examination. Intestinal and liver samples were tested by polymerase chain reaction (PCR) for the presence of ANV, duck enteritis virus, duck hepatitis virus 1 and Derzsy's disease virus. Multiple tissues were collected for histological examination and lesions were found to be confined to the kidney and intestine. Moderate focal interstitial and periglomerular mononuclear cell infiltrates (mostly lymphocytes and plasma cells) were detected in the kidney. The duodenum showed rather diffuse pericryptal mononuclear cell hyperplasia (lymphocytes) and fibroplasia. ANV was detected by PCR in all the intestinal samples, while no other viruses were found. Sequence comparisons of the portion of the open reading frame 1b encoding the RNA-dependent RNA polymerase gene confirmed that the virus detected and sequenced from ducklings shared high nucleotide and amino acid identities with ANV-1. Additional work is required to determine the clinicopathological significance of ANV infection in ducks.

One-year molecular survey of astrovirus infection in turkeys in Poland.

The presence of turkey astrovirus (TAstV) was monitored in meat-type turkey flocks in Poland in 2008. Clinical samples (10 individual faecal swabs/flock) from 77 flocks aged 1-19 weeks were collected from different regions of the country. RT-PCR experiments were performed for detection and molecular characterization of TAstV using four sets of primers within the RdRp gene (ORF1b). The prevalence of astrovirus was 34/77 (44.15%) in the flocks tested. TAstV type 2 was associated with 30 of 77 infections (38.9%), either alone or in mixed infections; TAstV type 1 was detected in 9 of 77 flocks (11.6%), either alone or in mixed infections; ANV was detected only in one flock (1.29%) by sequence analysis during this study. Phylogenetic analysis revealed genetic variability in the TAstV strains that were isolated. Some of Polish TAstV-2 strains were genetically related to the North American isolates; however, most of them formed a distinct subgroup of "European" isolates, suggesting their separate origin or evolution. Additionally, due to the high variability of the TAstV sequences, the most suitable method for TAstV typing seems to be sequencing.

Astrovirus infection induces sodium malabsorption and redistributes sodium hydrogen exchanger expression.

Astroviruses are known to be a leading cause of diarrhea in infants and the immunocompromised; however, our understanding of this endemic pathogen is limited. Histological analyses of astrovirus pathogenesis demonstrate clinical disease is not associated with changes to intestinal architecture, inflammation, or cell death. Recent studies in vitro have suggested that astroviruses induce actin rearrangement leading to loss of barrier function. The current study used the type-2 turkey astrovirus (TAstV-2) and turkey poult model of astrovirus disease to examine how astrovirus infection affects the ultrastructure and electrophysiology of the intestinal epithelium. These data demonstrate that infection results in changes to the epithelial ultrastructure, rearrangement of F-actin, decreased absorption of sodium, as well as redistribution of the sodium/hydrogen exchanger 3 (NHE3) from the membrane to the cytoplasm. Collectively, these data suggest astrovirus infection induces sodium malabsorption, possibly through redistribution of specific sodium transporters, which results in the development of an osmotic diarrhea.

A seroprevalence investigation of chicken astrovirus infections.

Two genetically different isolates of chicken astrovirus (CAstV), named CAstV612 and CAstV11672, which share low levels of antigenic relatedness in cross-indirect immunofluorescence (IIF) tests, have been identified recently. In the present study, separate IIF tests for detecting antibodies to the CAstV612 and CAstV11672 isolates have been used to determine the seroprevalences of CAstV infections in four generations of flocks involved in broiler chicken production. CAstV antibodies were detected in 78% (73% CAstV612; 46% CAstV11672) of serum samples from UK broiler flocks and in all 10 flocks tested, indicating that infections were very common. Twenty-three (96%) out of 24 and 26 (93%) out of 28 broiler parent flocks, aged 23 to 26 weeks from three UK organizations, were positive for antibody to CAstV612 and CAstV11672, respectively. Of 718 samples tested from these parent flocks, 415 (53%) were positive for either CAstV612 or CAstV11672 antibody. CAstV infections were also widespread in parent flocks, with screening of pooled serum samples showing that antibodies to both CAstVs were detected in flocks from seven other UK poultry organizations and in flocks from eight other European countries. The seropositivities for CAstVs were substantially less in grandparent (28%) and great grandparent (21%) flocks. Overall, higher seropositivities were observed for CAstV612 than for CAstV11672 in broiler, parent, grandparent and great-grandparent flocks. A limited study of 99 sera from 10 turkey breeder flocks showed low-level seropositivities for CAstV612 (9%) and CAstV11672 (2%), indicating that turkeys were infected with CAstVs or antigenically related viruses.