Novel avian coronavirus and fulminating disease in guinea fowl, France

Coronaviruses: Troubling Crown of the Animal Kingdom

The existence of coronaviruses has been known for many years. These viruses cause significant disease that primarily seems to affect agricultural species. Human coronavirus disease due to the 2002 outbreak of Severe Acute Respiratory Syndrome and the 2012 outbreak of Middle East Respiratory Syndrome made headlines; however, these outbreaks were controlled, and public concern quickly faded. This complacency ended in late 2019 when alarms were raised about a mysterious virus responsible for numerous illnesses and deaths in China. As we now know, this novel disease called Coronavirus Disease 2019 (COVID-19) was caused by Severe acute respiratory syndrome-related-coronavirus-2 (SARS-CoV-2) and rapidly became a worldwide pandemic. Luckily, decades of research into animal coronaviruses hastened our understanding of the genetics, structure, transmission, and pathogenesis of these viruses. Coronaviruses infect a wide range of wild and domestic animals, with significant economic impact in several agricultural species. Their large genome, low dependency on host cellular proteins, and frequent recombination allow coronaviruses to successfully cross species barriers and adapt to different hosts including humans. The study of the animal diseases provides an understanding of the virus biology and pathogenesis and has assisted in the rapid development of the SARS-CoV-2 vaccines. Here, we briefly review the classification, origin, etiology, transmission mechanisms, pathogenesis, clinical signs, diagnosis, treatment, and prevention strategies, including available vaccines, for coronaviruses that affect domestic, farm, laboratory, and wild animal species. We also briefly describe the coronaviruses that affect humans. Expanding our knowledge of this complex group of viruses will better prepare us to design strategies to prevent and/or minimize the impact of future coronavirus outbreaks.

Novel Virus Identification through Metagenomics: A Systematic Review

Metagenomic Next Generation Sequencing (mNGS) allows the evaluation of complex microbial communities, avoiding isolation and cultivation of each microbial species, and does not require prior knowledge of the microbial sequences present in the sample. Applications of mNGS include virome characterization, new virus discovery and full-length viral genome reconstruction, either from virus preparations enriched in culture or directly from clinical and environmental specimens. Here, we systematically reviewed studies that describe novel virus identification through mNGS from samples of different origin (plant, animal and environment). Without imposing time limits to the search, 379 publications were identified that met the search parameters. Sample types, geographical origin, enrichment and nucleic acid extraction methods, sequencing platforms, bioinformatic analytical steps and identified viral families were described. The review highlights mNGS as a feasible method for novel virus discovery from samples of different origins, describes which kind of heterogeneous experimental and analytical protocols are currently used and provides useful information such as the different commercial kits used for the purification of nucleic acids and bioinformatics analytical pipelines.

Genome Analysis of Goose-Origin Astroviruses Causing Fatal Gout in Shanghai, China Reveals One of Them Belonging to a Novel Type Is a Recombinant Strain

Since 2014, a goose-origin astroviruses disease, which is characterized by urate precipitation in viscera, has rapidly spread to major commercial goose provinces leading to huge economic losses in the poultry industry of China. In March 2020, a goose farm locates in Shanghai, China, where there was no goose astroviruses (GAstVs) infection reported before, experienced an outbreak of gout disease in geese. The etiological investigation was carried out by virus metagenomics and bacterial culture and two GAstVs strains, designated as CHSH01 and CHSH02, were determined. Their complete genomes were measured to 7,154 and 7,330 nt in length, excludingthe poly(A) tail, respectively, and had different genomic features and classifications. CHSH01 shared a very low sequence identity with other strains in terms of not only the complete genome but also different ORFs. Phylogenetic analysis showed CHSH02 belonged to GAstV-2, which was the predominant species in the geese with gout in China according to the previous study. Meanwhile, CHSH01 strain displayed low identity with other AstVs, and phylogenetic and recombination analysis suggested that CHSH01 belonging to a novel type was a recombinant strain, one parent strain of which was an AstV determined from a bar-headed goose (a kind of migrant bird). Moreover, the primary epidemiological investigation showed that the two strains were prevalent in the same goose farm and co-infection occurred. These findings arise the potential cross-species transmission of CHSH01 between domestic and wild fowl.

Diversity of Coronaviruses with Particular Attention to the Interspecies Transmission of SARS-CoV-2

Simple Summary

Coronaviruses are a broad group of viruses that may infect a wide range of animals, including humans. Despite the fact that each coronavirus has a limited host range, frequent interspecies transmission of coronaviruses across diverse hosts has resulted in a complex ecology. The recently discovered SARS-CoV-2 virus is the clearest evidence of the danger of a global pandemic spreading. Natural infection with SARS-CoV-2 has been reported in a variety of domestic and wild animals, which may complicate the virus’s epidemiology and influence its development. In this review, we discussed the potential determinants of SARS-CoV-2 interspecies transmission. Additionally, despite the efforts that have been made to control this pandemic and to implement the One Health policy, several problems, such as the role of animals in SARS-CoV-2 evolution and the dynamics of interspecies transmission, are still unanswered.

Abstract

In December 2019, the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was reported in China with serious impacts on global health and economy that is still ongoing. Although interspecies transmission of coronaviruses is common and well documented, each coronavirus has a narrowly restricted host range. Coronaviruses utilize different receptors to mediate membrane fusion and replication in the cell cytoplasm. The interplay between the receptor-binding domain (RBD) of coronaviruses and their coevolution are determinants for host susceptibility. The recently emerged SARS-CoV-2 caused the coronavirus disease 2019 (COVID-19) pandemic and has also been reported in domestic and wild animals, raising the question about the responsibility of animals in virus evolution. Additionally, the COVID-19 pandemic might also substantially have an impact on animal production for a long time. In the present review, we discussed the diversity of coronaviruses in animals and thus the diversity of their receptors. Moreover, the determinants of the susceptibility of SARS-CoV-2 in several animals, with special reference to the current evidence of SARS-CoV-2 in animals, were highlighted. Finally, we shed light on the urgent demand for the implementation of the One Health concept as a collaborative global approach to mitigate the threat for both humans and animals.

Description of the first isolates of guinea fowl corona and picornaviruses obtained from a case of guinea fowl fulminating enteritis

Guinea fowl fulminating enteritis has been reported in France since the 1970s. In 2014, a coronavirus was identified and appeared as a possible viral pathogen involved in the disease. In the present study, intestinal content from a guinea fowl involved in a new case of the disease in 2017 was analysed by deep sequencing, revealing the presence of a guinea fowl coronavirus (GfCoV) and a picornavirus (GfPic). Serial passage assays into the intra-amniotic cavity of 13-day-old specific pathogen-free chicken eggs and 20-day-old conventional guinea fowl eggs were attempted. In chicken eggs, isolation assays failed, but in guinea fowl eggs, both viruses were successfully obtained. Furthermore, two GfCoV and two GfPic isolates were obtained from the same bird but from different sections of its intestines. This shows that using eggs of the same species, in which the virus has been detected, can be the key for successful isolation. The consensus sequence of the full-length genomes of both GfCoV isolates was highly similar, and correlated to those previously described in terms of genome organization, ORF length and phylogenetic clustering. According to full-length genome analysis and the structure of the Internal Ribosome Entry Site, both GfPic isolates belong to the Anativirus genus and specifically the species Anativirus B. The availability of the first isolates of GfCoV and GfPic will now provide a means of assessing their pathogenicity in guinea fowl in controlled experimental conditions and to assess whether they are primary viral pathogens of the disease "guinea fowl fulminating enteritis".RESEARCH HIGHLIGHTSFirst isolation of guinea fowl coronaviruses and picornaviruses.Eggs homologous to the infected species are key for isolation.Isolates available to precisely evaluate the virus roles in fulminating enteritis.First full-length genome sequences of guinea fowl picornaviruses.

Diversity of Coronaviruses in Wild Representatives of the Aves Class in Poland

The revealed prevalence of coronaviruses in wild bird populations in Poland was 4.15% and the main reservoirs were birds from orders Anseriformes and Charadriiformes, with a prevalence of 3.51% and 5.59%, respectively. Gammacoronaviruses were detected more often than deltacoronaviruses, with detection rates of 3.5% and 0.7%, respectively. Gammacoronaviruses were detected in birds belonging to six orders, including Anseriformes, Charadriiformes, Columbiformes, Galliformes, Gruiformes, and Passeriformes, indicating a relatively wide host range. Interestingly, this was the only coronavirus detected in Anseriformes (3.51%), while in Charadriiformes, the prevalence was 3.1%. The identified gammacoronaviruses belonged to the Igacovirus and Brangacovirus subgeneras. Most of these were igacoviruses and formed a common phylogenetic group with a Duck Coronavirus 2714 and two with an Avian Coronavirus/Avian Coronavirus9203, while the viruses from the pigeons formed a distinct “pigeon-like” group, not yet officially represented. The presence of deltacoronaviruses was detected in birds belonging to three orders, Charadriiformes, Galliformes, and Suliformes indicating a narrower host range. Most identified deltacoronaviruses belonged to the Buldecovirus subgenus, while only one belonged to Herdecovirus. Interestingly, the majority of buldecoviruses were identified in gulls, and they formed a distinct phylogenetic lineage not represented by any officially ratified virus species. Another separate group of buldecoviruses, also not represented by the official species, was formed by a virus identified in a common snipe. Only one identified buldecovirus (from common pheasant) formed a group with the ratified species Coronavirus HKU15. The results obtained indicate the high diversity of detected coronaviruses, and thus also the need to update their taxonomy (establishing new representative virus species). The serological studies performed revealed antibodies against an infectious bronchitis virus in the sera of white storks and mallards.

Pathogenic evaluation of a turkey coronavirus isolate (TCoV NC1743) in turkey poults for establishing a TCoV disease model

Turkey coronavirus (TCoV) can cause a highly contagious enteric disease in turkeys with severe economic losses in the global turkey industry. To date, no commercial vaccines are available for control of the disease. In the present study, we isolated a field strain (NC1743) of TCoV and evaluated its pathogenicity in specific-pathogen-free (SPF) turkey poults to establish a TCoV disease model. The results showed that the TCoV NC1743 isolate was pathogenic to turkey poults with a minimal infectious dose at 10⁶ EID₅₀/bird. About 50 % of one-day-old SPF turkeys infected with the virus's minimal infectious dose exhibited typical enteric disease signs and lesions from 6 days post-infection (dpi) to the end of the experiment (21 dpi). In contrast, fewer than 20 % of older turkeys (1- or 2-week-old) infected with the same amount of TCoV displayed enteric disease signs, which disappeared after 15-18 dpi. Although all infected turkeys, regardless of age, shed TCoV, the older turkeys shed less virus than the younger birds, and 50 % of the 2-week-old birds even cleared the virus at 21 dpi. Furthermore, the viral infection caused day-old turkeys more body-weight-gain reduction than older birds. The overall data demonstrated that the TCoV NC1743 isolate is a highly pathogenic strain and younger turkeys are more susceptible to TCoV infection than older birds. Thus, one-day-old turkeys infected with the minimal infectious dose of TCoV NC1743 could be used as a TCoV disease model to study the disease pathogenesis, and the TCoV NC1743 strain could be used as a challenge virus to evaluate a vaccine protective efficacy.

[General introduction to animal and human coronaviruses]

Les coronavirus sont des virus à ARN classés en Alphacoronavirus, Betacoronavirus, Gammacoronavirus et Deltacoronavirus. Leur nom vient de leur conformation avec la présence de spicules formant une sorte de couronne. Les Alphacoronavirus et les Betacoronavirus (genre où l’on observe des zoonoses) semblent provenir des chauves-souris alors que les oiseaux seraient à l’origine des Gammacoronavirus et des Deltacoronavirus. Le premier coronavirus identifié fut celui de la bronchite infectieuse aviaire en 1931 aux États-Unis alors que les premiers coronavirus n’ont été décrits chez l’Homme que dans les années 1960. C’est pourquoi on connaissait surtout des coronavirus dans la communauté vétérinaire. La plupart des Alphacoronavirus sont spécifiques d’espèce. Ils peuvent être responsables de maladies graves notamment chez le chat (une forme entérique–FECV- et une forme responsable de la péritonite infectieuse féline–FIPV), la gastroentérite transmissible (GET) du porcelet et la diarrhée épidémique porcine (DEP), la coronavirose respiratoire porcin (PRCV). Enfin, un deltacoronavirus peut être rencontré à la fois chez le porc (PD CoV UKU15) et les oiseaux.

Recombinant turkey coronavirus: are some S gene structures of gammacoronaviruses especially prone to exchange?

The objective of the present study was to characterize the atypical turkey coronavirus strain detected in a commercial meat turkey farm in Poland. Using the viral metagenomics approach, we obtained a complete genome sequence of coronavirus, isolated from duodenum samples of animals suffering from acute enteritis. The nearly full-length genome consisted of 27,614 nucleotides and presented a typical genetic organization similar to that of Polish infectious bronchitis virus (IBV) or French turkey coronavirus/guinea fowl coronavirus strains. Phylogenetic analysis based on both the full-length genome and the whole S gene suggested that gCoV/Tk/Poland/G160/2016 is related to turkey and guinea fowl coronavirus and not IBV strains. Sequence analysis of the genome revealed unique genetic characteristics of the present strain, demonstrating that the virus emerged as a result of the exchange of the S gene of IBV GI-19 lineage with the S gene related to the North American turkey coronaviruses and French guinea fowl coronaviruses. Analysis of earlier, similar recombinations suggests that both the S gene structures may be particularly mobile, willingly switching between different gammacoronavirus genomic backbones. The identified recombinant caused a severe course of the disease, which may imply that it is in the first phase of breaking the barriers between different bird species.

Pathology of Coronavirus Infections: A Review of Lesions in Animals in the One-Health Perspective

Coronaviruses (CoVs) are worldwide distributed RNA-viruses affecting several species, including humans, and causing a broad spectrum of diseases. Historically, they have not been considered a severe threat to public health until two outbreaks of COVs-related atypical human pneumonia derived from animal hosts appeared in 2002 and in 2012. The concern related to CoVs infection dramatically rose after the COVID-19 global outbreak, for which a spill-over from wild animals is also most likely. In light of this CoV zoonotic risk, and their ability to adapt to new species and dramatically spread, it appears pivotal to understand the pathophysiology and mechanisms of tissue injury of known CoVs within the "One-Health" concept. This review specifically describes all CoVs diseases in animals, schematically representing the tissue damage and summarizing the major lesions in an attempt to compare and put them in relation, also with human infections. Some information on pathogenesis and genetic diversity is also included. Investigating the lesions and distribution of CoVs can be crucial to understand and monitor the evolution of these viruses as well as of other pathogens and to further deepen the pathogenesis and transmission of this disease to help public health preventive measures and therapies.

Animal Coronaviruses in the Light of COVID-19

Coronaviruses are extremely susceptible to genetic changes due to the characteristic features of the genome structure, life cycle and environmental pressure. Their remarkable variability means that they can infect many different species of animals and cause different disease symptoms. Moreover, in some situations, coronaviruses might be transmitted across species. Although they are commonly found in farm, companion and wild animals, causing clinical and sometimes serious signs resulting in significant economic losses, not all of them have been classified by the World Organization for Animal Health (OIE) as hazardous and included on the list of notifiable diseases. Currently, only three diseases caused by coronaviruses are on the OIE list of notifiable terrestrial and aquatic animal diseases. However, none of these three entails any administrative measures. The emergence of the SARS-CoV-2 infections that have caused the COVID-19 pandemic in humans has proved that the occurrence and variability of coronaviruses is highly underestimated in the animal reservoir and reminded us of the critical importance of the One Health approach. Therefore, domestic and wild animals should be intensively monitored, both to broaden our knowledge of the viruses circulating among them and to understand the mechanisms of the emergence of viruses of relevance to animal and human health.

On the Coronaviruses and Their Associations with the Aquatic Environment and Wastewater

The outbreak of Coronavirus Disease 2019 (COVID-19), a severe respiratory disease caused by betacoronavirus SARS-CoV-2, in 2019 that further developed into a pandemic has received an unprecedented response from the scientific community and sparked a general research interest into the biology and ecology of Coronaviridae, a family of positive-sense single-stranded RNA viruses. Aquatic environments, lakes, rivers and ponds, are important habitats for bats and birds, which are hosts for various coronavirus species and strains and which shed viral particles in their feces. It is therefore of high interest to fully explore the role that aquatic environments may play in coronavirus spread, including cross-species transmissions. Besides the respiratory tract, coronaviruses pathogenic to humans can also infect the digestive system and be subsequently defecated. Considering this, it is pivotal to understand whether wastewater can play a role in their dissemination, particularly in areas with poor sanitation. This review provides an overview of the taxonomy, molecular biology, natural reservoirs and pathogenicity of coronaviruses; outlines their potential to survive in aquatic environments and wastewater; and demonstrates their association with aquatic biota, mainly waterfowl. It also calls for further, interdisciplinary research in the field of aquatic virology to explore the potential hotspots of coronaviruses in the aquatic environment and the routes through which they may enter it.

Spotlight on avian coronaviruses

Coronaviruses (CoVs) mainly cause enteric and/or respiratory signs. Mammalian CoVs including COVID-19 (now officially named SARS-CoV-2) belong to either the Alphacoronavirus or Betacoronavirus genera. In birds, the majority of the known CoVs belong to the Gammacoronavirus genus, whilst a small number are classified as Deltacoronaviruses. Gammacoronaviruses continue to be reported in an increasing number of avian species, generally by detection of viral RNA. Apart from infectious bronchitis virus in chickens, the only avian species in which CoV has been definitively associated with disease are the turkey, pheasant and guinea fowl. Whilst there is strong evidence for recombination between gammacoronaviruses of different avian species, and between betacoronaviruses in different mammals, evidence of recombination between coronaviruses of different genera is lacking. Furthermore, the recombination of an alpha or betacoronavirus with a gammacoronavirus is extremely unlikely. For recombination to happen, the two viruses would need to be present in the same cell of the same animal at the same time, a highly unlikely scenario as they cannot replicate in the same host!

Global Transmission, Spatial Segregation, and Recombination Determine the Long-Term Evolution and Epidemiology of Bovine Coronaviruses

Bovine coronavirus (BCoV) is widespread in cattle and wild ruminant populations throughout the world. The virus causes neonatal calf diarrhea and winter dysentery in adult cattle, as well as upper and lower respiratory tract infection in young cattle. We isolated and deep sequenced whole genomes of BCoV from calves with respiratory distress in the south–west of France and conducted a comparative genome analysis using globally collected BCoV sequences to provide insights into the genomic characteristics, evolutionary origins, and global diversity of BCoV. Molecular clock analyses allowed us to estimate that the BCoV ancestor emerged in the 1940s, and that two geographically distinct lineages diverged from the 1960s–1970s. A recombination event in the spike gene (breakpoint at nt 1100) may be at the origin of the genetic divergence sixty years ago. Little evidence of genetic mixing between the spatially segregated lineages was found, suggesting that BCoV genetic diversity is a result of a global transmission pathway that occurred during the last century. However, we found variation in evolution rates between the European and non-European lineages indicating differences in virus ecology.

Novel human coronavirus (SARS-CoV-2): A lesson from animal coronaviruses

The recent pandemic caused by the novel human coronavirus, referrred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), not only is having a great impact on the health care systems and economies in all continents but it is also causing radical changes of common habits and life styles. The novel coronavirus (CoV) recognises, with high probability, a zoonotic origin but the role of animals in the SARS-CoV-2 epidemiology is still largely unknown. However, CoVs have been known in animals since several decades, so that veterinary coronavirologists have a great expertise on how to face CoV infections in animals, which could represent a model for SARS-CoV-2 infection in humans. In the present paper, we provide an up-to-date review of the literature currently available on animal CoVs, focusing on the molecular mechanisms that are responsible for the emergence of novel CoV strains with different antigenic, biologic and/or pathogenetic features. A full comprehension of the mechanisms driving the evolution of animal CoVs will help better understand the emergence, spreading, and evolution of SARS-CoV-2.

Coronaviridae: 100,000 Years of Emergence and Reemergence

The coronavirus family (Coronaviridae) is a positive-sense single-stranded RNA, with a size of 27 kb. These viruses have a potential species specificity and interspecies transmission. The interspecies transmission of viruses from one host species to another is a major factor responsible for the majority of emerging and reemerging infections. The Coronaviridae is one of the most popular emerging viral families that threaten to the public health.

Metagenomics revealing new virus species in farm and pet animals and aquaculture

Viral metagenomics is slowly taking over the traditional and widely used molecular techniques for the investigation of pathogenic viruses responsible for illness and inflicting great economic burden on the farm animal industry. Owing to the continued improvements in sequencing technologies and the dramatic reduction of per base costs of sequencing the use of next generation sequencing have been key factors in this progress. Discoveries linked to viral metagenomics are expected to be beneficial to the field of veterinary medicine starting from the development of better diagnostic assays to the design of new subunit vaccines with minimal investments. With these achievements the research has taken a giant leap even toward the better healthcare of animals and, as a result, the animal sector could be growing at an unprecedented pace.

Guinea Fowl Coronavirus Diversity Has Phenotypic Consequences for Glycan and Tissue Binding

Avian coronaviruses cause major global problems in the poultry industry. As causative agents of huge economic losses, the detection and understanding of the molecular determinants of viral tropism are of ultimate importance. Here, we set out to study those parameters and obtained in-depth insight into the virus-host interactions of guinea fowl coronavirus (GfCoV). Our data indicate that diversity in GfCoV viral attachment proteins results in differences in degrees of affinity for glycan receptors, as well as altered avidity for intestinal tract tissues, which might have consequences for GfCoV tissue tropism and pathogenesis in guinea fowls.

Guinea fowl coronavirus (GfCoV) causes fulminating enteritis that can result in a daily death rate of 20% in guinea fowl flocks. Here, we studied GfCoV diversity and evaluated its phenotypic consequences. Over the period of 2014 to 2016, affected guinea fowl flocks were sampled in France, and avian coronavirus presence was confirmed by PCR on intestinal content and immunohistochemistry of intestinal tissue. Sequencing revealed 89% amino acid identity between the viral attachment protein S1 of GfCoV/2014 and that of the previously identified GfCoV/2011. To study the receptor interactions as a determinant for tropism and pathogenicity, recombinant S1 proteins were produced and analyzed by glycan and tissue arrays. Glycan array analysis revealed that, in addition to the previously elucidated biantennary di-N-acetyllactosamine (diLacNAc) receptor, viral attachment S1 proteins from GfCoV/2014 and GfCoV/2011 can bind to glycans capped with alpha-2,6-linked sialic acids. Interestingly, recombinant GfCoV/2014 S1 has an increased affinity for these glycans compared to that of GfCoV/2011 S1, which was in agreement with the increased avidity of GfCoV/2014 S1 for gastrointestinal tract tissues. Enzymatic removal of receptors from tissues before application of spike proteins confirmed the specificity of S1 tissue binding. Overall, we demonstrate that diversity in GfCoV S1 proteins results in differences in glycan and tissue binding properties.

IMPORTANCE Avian coronaviruses cause major global problems in the poultry industry. As causative agents of huge economic losses, the detection and understanding of the molecular determinants of viral tropism are of ultimate importance. Here, we set out to study those parameters and obtained in-depth insight into the virus-host interactions of guinea fowl coronavirus (GfCoV). Our data indicate that diversity in GfCoV viral attachment proteins results in differences in degrees of affinity for glycan receptors, as well as altered avidity for intestinal tract tissues, which might have consequences for GfCoV tissue tropism and pathogenesis in guinea fowls.

Whole genome characterisation of quail deltacoronavirus detected in Poland

Quail deltacoronavirus (QdCoV) described for the first time in the United Arab Emirates in 2018 belongs to the same deltacoronavirus species as viruses discovered in swine and tree sparrows. The full-length genome of QdCoV detected in quails with enteritis in Poland has similar organization as Middle Eastern viruses although there is no NSP7c gene. The overall degree of nucleotide sequence identity was 92.4-92.6% between Polish PL/G032/2015 and Middle Eastern UAE-HKU30 QdCoV isolates. The sequences of the individual genes show similar nucleotide identities in the range of 91.4-94.7% with the exception of the S gene with lower identity of 85.6-85.7%. The most variable part of the S gene is its fragment encoding the N-terminal domain of the S protein which is responsible for receptor binding. The amino acid homology in this region between PL/G032/2015 and UAE-HKU30 QdCoVs was 74.5-74.7%. In contrast, the C-terminal domain of the S protein which is responsible for membrane fusion had an amino acid homology of 96.9%. In the phylogenetic tree, PL/G032/2015 branched separately but clustered with the UAE-HKU30 QdCoV isolates. These data suggest that PL/G032/2015 could be a new genetic/serologic variant of QdCoV.

Coronaviruses in Avian Species - Review with Focus on Epidemiology and Diagnosis in Wild Birds

Coronaviruses (CoVs) are a large group of enveloped viruses with a single-strand RNA genome, which continuously circulate in mammals and birds and pose a threat to livestock, companion animals, and humans. CoVs harboured by avian species are classified to the genera gamma- and deltacoronaviruses. Within the gamma-CoVs the main representative is avian coronavirus, a taxonomic name which includes the highly contagious infectious bronchitis viruses (IBVs) in chickens and similar viruses infecting other domestic birds such as turkeys, guinea fowls, or quails. Additionally, IBVs have been detected in healthy wild birds, demonstrating that they may act as the vector between domestic and free-living birds. Moreover, CoVs other than IBVs, are identified in wild birds, which suggests that wild birds play a key role in the epidemiology of other gammaCoVs and deltaCoVs. Development of molecular techniques has significantly improved knowledge of the prevalence of CoVs in avian species. The methods adopted in monitoring studies of CoVs in different avian species are mainly based on detection of conservative regions within the viral replicase, nucleocapsid genes, and 3'UTR or 5'UTR. The purpose of this review is to summarise recent discoveries in the areas of epidemiology and diagnosis of CoVs in avian species and to understand the role of wild birds in the virus distribution.

Serological and Molecular Surveillance of Infectious Bronchitis Virus Infection in Free-Range Chickens and Guinea Fowls in the Ga-East District of Ghana

Infectious bronchitis is an economically important disease with worldwide distribution. Information is available on the presence of infectious bronchitis virus in commercial chicken in parts of Ghana but there is no information on free-range poultry and guinea fowls in the country. Possible IBV infections among free-range chickens and guinea fowls in Abokobi and Frafraha communities in the Ga-East district of the Greater Accra Region of Ghana were investigated using serology and PCR. Blood, tracheal, and cloacal swabs were obtained from 219 free-range chickens and guinea fowls with no respiratory symptoms and no history of IBV vaccination. Sera were evaluated for IBV antibodies by ELISA using commercial IBV test kit from IDEXX, Inc., USA. Swab samples were evaluated for S1 glycoprotein gene by one-step RT PCR. All the swab samples tested negative for IBV. 16% of all tested sera were positive for IBV. IBV seroprevalence in guinea fowls was 0%. 21.2% of sera from local chickens were positive for IBV. The seroprevalence of IBV among local chickens from Frafraha was 30% and that of Abokobi was 7.7%. This study shows exposure of local chickens in the study communities to IBV.

Global distributions and strain diversity of avian infectious bronchitis virus: a review

The poultry industry faces challenge amidst global food security crisis. Infectious bronchitis is one of the most important viral infections that cause huge economic loss to the poultry industry worldwide. The causative agent, infectious bronchitis virus (IBV) is an RNA virus with great ability for mutation and recombination; thus, capable of generating new virus strains that are difficult to control. There are many IBV strains found worldwide, including the Massachusetts, 4/91, D274, and QX-like strains that can be grouped under the classic or variant serotypes. Currently, information on the epidemiology, strain diversity, and global distribution of IBV has not been comprehensively reported. This review is an update of current knowledge on the distribution, genetic relationship, and diversity of the IBV strains found worldwide.

Genotyping of turkey coronavirus field isolates from various geographic locations in the Unites States based on the spike gene

Turkey flocks have experienced turkey coronaviral enteritis sporadically in the United States since the 1990s. Twenty-four field isolates of turkey coronavirus (TCoV) from multiple states in the United States were recovered from 1994 to 2010 to determine the genetic relationships among them. The entire spike (S) gene of each TCoV isolate was amplified and sequenced. Pairwise comparisons were performed using the Clustal W program, revealing 90.0 % to 98.4 % sequence identity in the full-length S protein, 77.6 % to 96.6 % in the amino terminus of the S1 subunit (containing one hypervariable region in S1a), and 92.1 % to 99.3 % in the S2 subunit at the deduced amino acid sequence level. The conserved motifs, including two cleavage recognition sequences of the S protein, two heptad repeats, the transmembrane domain, and the Golgi retention signal were identified in all TCoV isolates. Phylogenetic analysis based on the full-length S gene was used to distinguish North American TCoV isolates from French TCoV isolates. Among the North American TCoV isolates, three distinct genetic groups with 100 % bootstrap support were observed. North Carolina isolates formed group I, Texas isolates formed group II, and Minnesota isolates formed Group III. The S genes of 24 TCoV isolates from the United States remained conserved because they contained predominantly synonymous substitutions. The findings of the present study suggest endemic circulation of distinct TCoV genotypes in different geographic locations.

Novel Receptor Specificity of Avian Gammacoronaviruses That Cause Enteritis

Viruses exploit molecules on the target membrane as receptors for attachment and entry into host cells. Thus, receptor expression patterns can define viral tissue tropism and might to some extent predict the susceptibility of a host to a particular virus. Previously, others and we have shown that respiratory pathogens of the genus Gammacoronavirus, including chicken infectious bronchitis virus (IBV), require specific α2,3-linked sialylated glycans for attachment and entry. Here, we studied determinants of binding of enterotropic avian gammacoronaviruses, including turkey coronavirus (TCoV), guineafowl coronavirus (GfCoV), and quail coronavirus (QCoV), which are evolutionarily distant from respiratory avian coronaviruses based on the viral attachment protein spike (S1). We profiled the binding of recombinantly expressed S1 proteins of TCoV, GfCoV, and QCoV to tissues of their respective hosts. Protein histochemistry showed that the tissue binding specificity of S1 proteins of turkey, quail, and guineafowl CoVs was limited to intestinal tissues of each particular host, in accordance with the reported pathogenicity of these viruses in vivo. Glycan array analyses revealed that, in contrast to the S1 protein of IBV, S1 proteins of enteric gammacoronaviruses recognize a unique set of nonsialylated type 2 poly-N-acetyl-lactosamines. Lectin histochemistry as well as tissue binding patterns of TCoV S1 further indicated that these complex N-glycans are prominently expressed on the intestinal tract of various avian species. In conclusion, our data demonstrate not only that enteric gammacoronaviruses recognize a novel glycan receptor but also that enterotropism may be correlated with the high specificity of spike proteins for such glycans expressed in the intestines of the avian host.

IMPORTANCE

Avian coronaviruses are economically important viruses for the poultry industry. While infectious bronchitis virus (IBV), a respiratory pathogen of chickens, is rather well known, other viruses of the genus Gammacoronavirus, including those causing enteric disease, are hardly studied. In turkey, guineafowl, and quail, coronaviruses have been reported to be the major causative agent of enteric diseases. Specifically, turkey coronavirus outbreaks have been reported in North America, Europe, and Australia for several decades. Recently, a gammacoronavirus was isolated from guineafowl with fulminating disease. To date, it is not clear why these avian coronaviruses are enteropathogenic, whereas other closely related avian coronaviruses like IBV cause respiratory disease. A comprehensive understanding of the tropism and pathogenicity of these viruses explained by their receptor specificity and receptor expression on tissues was therefore needed. Here, we identify a novel glycan receptor for enteric avian coronaviruses, which will further support the development of vaccines.

Full genome sequence of guinea fowl coronavirus associated with fulminating disease

Guinea fowl coronavirus (GfCoV), a recently characterized avian coronavirus, was identified from outbreaks of fulminating disease (peracute enteritis) in guinea fowl in France. The full-length genomic sequence was determined to better understand its genetic relationship with avian coronaviruses. The full-length coding genome sequence was 26,985 nucleotides long with 11 open reading frames and no hemagglutinin–esterase gene: a genome organization identical to that of turkey coronavirus [5′ untranslated region (UTR)—replicase (ORFs 1a, 1ab)—spike (S) protein—ORF3 (ORFs 3a, 3b)—small envelop (E or 3c) protein—membrane (M) protein—ORF5 (ORFs 4b, 4c, 5a, 5b)—nucleocapsid (N) protein (ORFs N and 6b)—3′ UTR]. This is the first complete genome sequence of a GfCoV and confirms that the new virus belongs to group gammacoronaviruses.

Cross-species transmission and emergence of novel viruses from birds

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The role of birds in cross-species transmission and emergence of novel viruses such as avian influenza A viruses are discussed.

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The novel avian viruses identified between 2012 and 2014 are summarized.

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The concept of ‘pathogen augmentation’ is introduced.

Birds, the only living member of the Dinosauria clade, are flying warm-blooded vertebrates displaying high species biodiversity, roosting and migratory behavior, and a unique adaptive immune system. Birds provide the natural reservoir for numerous viral species and therefore gene source for evolution, emergence and dissemination of novel viruses. The intrusions of human into natural habitats of wild birds, the domestication of wild birds as pets or racing birds, and the increasing poultry consumption by human have facilitated avian viruses to cross species barriers to cause zoonosis. Recently, a novel adenovirus was exclusively found in birds causing an outbreak of Chlamydophila psittaci infection among birds and humans. Instead of being the primary cause of an outbreak by jumping directly from bird to human, a novel avian virus can be an augmenter of another zoonotic agent causing the outbreak. A comprehensive avian virome will improve our understanding of birds’ evolutionary dynamics.

Identification of a novel coronavirus from guinea fowl using metagenomics

While classical virology techniques such as virus culture, electron microscopy, or classical PCR had been unsuccessful in identifying the causative agent responsible for the fulminating disease of guinea fowl, we identified a novel avian gammacoronavirus associated with the disease using metagenomics. Next-generation sequencing is an unbiased approach that allows the sequencing of virtually all the genetic material present in a given sample.

The avian coronavirus spike protein

Avian coronaviruses of the genus Gammacoronavirus are represented by infectious bronchitis virus (IBV), the coronavirus of chicken. IBV causes a highly contagious disease affecting the respiratory tract and, depending on the strain, other tissues including the reproductive and urogenital tract. The control of IBV in the field is hampered by the many different strains circulating worldwide and the limited protection across strains due to serotype diversity. This diversity is believed to be due to the amino acid variation in the S1 domain of the major viral attachment protein spike. In the last years, much effort has been undertaken to address the role of the avian coronavirus spike protein in the various steps of the virus' live cycle. Various models have successfully been developed to elucidate the contribution of the spike in binding of the virus to cells, entry of cell culture cells and organ explants, and the in vivo tropism and pathogenesis. This review will give an overview of the literature on avian coronavirus spike proteins with particular focus on our recent studies on binding of recombinant soluble spike protein to chicken tissues. With this, we aim to summarize the current understanding on the avian coronavirus spike's contribution to host and tissue predilections, pathogenesis, as well as its role in therapeutic and protective interventions.