Wild birds as reservoirs for diverse and abundant gamma- and deltacoronaviruses

Best Molecular Tools to Investigate Coronavirus Diversity in Mammals: A Comparison

Coronaviruses (CoVs) are widespread and highly diversified in wildlife and domestic mammals and can emerge as zoonotic or epizootic pathogens and consequently host shift from these reservoirs, highlighting the importance of veterinary surveillance. All genera can be found in mammals, with α and β showing the highest frequency and diversification. The aims of this study were to review the literature for features of CoV surveillance in animals, to test widely used molecular protocols, and to identify the most effective one in terms of spectrum and sensitivity. We combined a literature review with analyses in silico and in vitro using viral strains and archive field samples. We found that most protocols defined as pan-coronavirus are strongly biased towards α- and β-CoVs and show medium-low sensitivity. The best results were observed using our new protocol, showing LoD 100 PFU/mL for SARS-CoV-2, 50 TCID50/mL for CaCoV, 0.39 TCID50/mL for BoCoV, and 9 ± 1 log2 ×10-5 HA for IBV. The protocol successfully confirmed the positivity for a broad range of CoVs in 30/30 field samples. Our study points out that pan-CoV surveillance in mammals could be strongly improved in sensitivity and spectrum and propose the application of a new RT-PCR assay, which is able to detect CoVs from all four genera, with an optimal sensitivity for α-, β-, and γ-.

Evolutionary Dynamics and Epidemiology of Endemic and Emerging Coronaviruses in Humans, Domestic Animals, and Wildlife

Diverse coronavirus (CoV) strains can infect both humans and animals and produce various diseases. CoVs have caused three epidemics and pandemics in the last two decades, and caused a severe impact on public health and the global economy. Therefore, it is of utmost importance to understand the emergence and evolution of endemic and emerging CoV diversity in humans and animals. For diverse bird species, the Infectious Bronchitis Virus is a significant one, whereas feline enteric and canine coronavirus, recombined to produce feline infectious peritonitis virus, infects wild cats. Bovine and canine CoVs have ancestral relationships, while porcine CoVs, especially SADS-CoV, can cross species barriers. Bats are considered as the natural host of diverse strains of alpha and beta coronaviruses. Though MERS-CoV is significant for both camels and humans, humans are nonetheless affected more severely. MERS-CoV cases have been reported mainly in the Arabic peninsula since 2012. To date, seven CoV strains have infected humans, all descended from animals. The severe acute respiratory syndrome coronaviruses (SARS-CoV and SARS-CoV-2) are presumed to be originated in Rhinolopoid bats that severely infect humans with spillover to multiple domestic and wild animals. Emerging alpha and delta variants of SARS-CoV-2 were detected in pets and wild animals. Still, the intermediate hosts and all susceptible animal species remain unknown. SARS-CoV-2 might not be the last CoV to cross the species barrier. Hence, we recommend developing a universal CoV vaccine for humans so that any future outbreak can be prevented effectively. Furthermore, a One Health approach coronavirus surveillance should be implemented at human-animal interfaces to detect novel coronaviruses before emerging to humans and to prevent future epidemics and pandemics.

SARS-Coronavirus 2, A Metabolic Reprogrammer: A Review in the Context of the Possible Therapeutic Strategies

Novel coronavirus, SARS-CoV-2 is advancing at a staggering pace to devastate the health care system and foster the concerns over public health. In contrast to the past outbreaks, coronaviruses aren't clinging themselves as a strict respiratory virus. Rather, becoming a multifaceted virus, it affects multiple organs by interrupting a number of metabolic pathways leading to significant rates of morbidity and mortality. Following infection they rigorously reprogram multiple metabolic pathways of glucose, lipid, protein, nucleic acid and their metabolites to extract adequate energy and carbon skeletons required for their existence and further molecular constructions inside a host cell. Although the mechanism of these alterations are yet to be known, the impact of these reprogramming is reflected in the hyper inflammatory responses, so called cytokine storm and the hindrance of host immune defence system. The metabolic reprogramming during SARS-CoV-2 infection needs to be considered while devising therapeutic strategies to combat the disease and its further complication. The inhibitors of cholesterol and phospholipids synthesis and cell membrane lipid raft of the host cell can, to a great extent, control the viral load and further infection. Depletion of energy source by inhibiting the activation of glycolytic and hexoseamine biosynthetic pathway can also augment the antiviral therapy. The cross talk between these pathways also necessitates the inhibition of amino acid catabolism and tryptophan metabolism. A combinatorial strategy which can address the cross talks between the metabolic pathways might be more effective than a single approach and the infection stage and timing of therapy will also influence the effectiveness of the antiviral approach. We herein focus on the different metabolic alterations during the course of virus infection that help to exploit the cellular machinery and devise a therapeutic strategy which promotes resistance to viral infection and can augment body's antivirulence mechanisms. This review may cast the light into the possibilities of targeting altered metabolic pathways to defend virus infection in a new perspective.

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.

Infectious bronchitis virus in Australia: a model of coronavirus evolution - a review

Infectious bronchitis virus (IBV) was first isolated in Australia in 1962. Ongoing surveillance and characterization of Australian IBVs have shown that they have evolved separately from strains found throughout the rest of the world, resulting in the evolution of a range of unique strains and changes in the dominant wild-type strains, affecting tissue tropism, pathogenicity, antigenicity, and gene arrangement. Between 1961 and 1976 highly nephropathogenic genotype GI-5 and GI-6 strains, causing mortalities of 40% to 100%, predominated, while strains causing mainly respiratory disease, with lower mortality rates, have predominated since then. Since 1988, viruses belonging to two distinct and novel genotypes, GIII and GV, have been detected. The genome organization of the GIII strains has not been seen in any other gammacoronavirus. Mutations that emerged soon after the introduction of vaccination, incursion of strains with a novel lineage from unknown sources, recombination between IBVs from different genetic lineages, and gene translocations and deletions have contributed to an increasingly complex IBV population. These processes and the consequences of this variation for the biology of these viruses provide an insight into the evolution of endemic coronaviruses during their control by vaccination and may provide a better understanding of the potential for evolution of other coronaviruses, including SARS-CoV-2. Furthermore, the continuing capacity of attenuated IBV vaccines developed over 40 years ago to provide protection against viruses in the same genetic lineage provides some assurance that coronavirus vaccines developed to control other coronaviruses may continue to be effective for an extended period.

Modular Evolution of Coronavirus Genomes

The viral family Coronaviridae comprises four genera, termed Alpha-, Beta-, Gamma-, and Deltacoronavirus. Recombination events have been described in many coronaviruses infecting humans and other animals. However, formal analysis of the recombination patterns, both in terms of the involved genome regions and the extent of genetic divergence between partners, are scarce. Common methods of recombination detection based on phylogenetic incongruences (e.g., a phylogenetic compatibility matrix) may fail in cases where too many events diminish the phylogenetic signal. Thus, an approach comparing genetic distances in distinct genome regions (pairwise distance deviation matrix) was set up. In alpha, beta, and delta-coronaviruses, a low incidence of recombination between closely related viruses was evident in all genome regions, but it was more extensive between the spike gene and other genome regions. In contrast, avian gammacoronaviruses recombined extensively and exist as a global cloud of genes with poorly corresponding genetic distances in different parts of the genome. Spike, but not other structural proteins, was most commonly exchanged between coronaviruses. Recombination patterns differed between coronavirus genera and corresponded to the modular structure of the spike: recombination traces were more pronounced between spike domains (N-terminal and C-terminal parts of S1 and S2) than within domains. The variability of possible recombination events and their uneven distribution over the genome suggest that compatibility of genes, rather than mechanistic or ecological limitations, shapes recombination patterns in coronaviruses.

Replication and vaccine protection of multiple infectious bronchitis virus strains in pheasants (Phasianus colchicus)

This study demonstrates that infectious bronchitis virus (IBV) strain M41, which is pathogenic for chickens, is nonpathogenic for pheasants. However, M41 replicated in the respiratory tracts of most inoculated pheasants and the virus was shed from their respiratory tracts in the early stages of infection (4 and 8 dpc). Similarly, the attenuated IBV H120 vaccine strain also replicated and the virus was shed from their respiratory tracts of most inoculated pheasants, whereas the pheasant coronavirus (PhCoV) I0623/17 replicated in the respiratory tracts of all challenged pheasants, which then shed virus for a long period of time. Strain M41 also replicated in selected tissues of the inoculated pheasants, including the lung, kidney, proventriculus, and cecal tonsil, although the viral titers were very low. Therefore, it was important to establish whether the H120 vaccine, which has a limited replication capacity in pheasants, induces a protective immune response to both "homologous" M41 and "heterologous" I0623/17 challenge. Vaccination with H120 induced humoral responses, and the replication of M41 was reduced or restricted in the tissues of the H120-vaccinated pheasants compared with its replication in unvaccinated birds. This implies that partial protection was conferred on pheasants by vaccination with the H120 vaccine. Prolonged viral replication and a large number of birds shedding virus into the respiratory tract were also observed in the unvaccinated pheasants after inoculation with M41. However, only limited protection against challenge with PhCoV I0623/17 was conferred on pheasants vaccinated with H120, largely because the replication of H120 in pheasants was limited, thus, limiting the immune responses induced by it. The low amino acid identity of the S1 subunit of the S proteins of H120 and I0623/17 might also account, at least in part, for the poor cross-protective immunity induced by H120. These results suggest that further work is required to rationally design vaccines that confer effective protection against PhCoV infection in commercial pheasant stocks.

Functions of Coronavirus Accessory Proteins: Overview of the State of the Art

Coronavirus accessory proteins are a unique set of proteins whose genes are interspersed among or within the genes encoding structural proteins. Different coronavirus genera, or even different species within the same coronavirus genus, encode varying amounts of accessory proteins, leading to genus- or species-specificity. Though accessory proteins are dispensable for the replication of coronavirus in vitro, they play important roles in regulating innate immunity, viral proliferation, and pathogenicity. The function of accessory proteins on virus infection and pathogenesis is an area of particular interest. In this review, we summarize the current knowledge on accessory proteins of several representative coronaviruses that infect humans or animals, including the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with an emphasis on their roles in interaction between virus and host, mainly involving stress response, innate immunity, autophagy, and apoptosis. The cross-talking among these pathways is also discussed.

Exploring SARS-COV-2 structural proteins to design a multi-epitope vaccine using immunoinformatics approach: An in silico study

In December 2019, a new virus called SARS-CoV-2 was reported in China and quickly spread to other parts of the world. The development of SARS-COV-2 vaccines has recently received much attention from numerous researchers. The present study aims to design an effective multi-epitope vaccine against SARS-COV-2 using the reverse vaccinology method. In this regard, structural proteins from SARS-COV-2, including the spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins, were selected as target antigens for epitope prediction. A total of five helper T lymphocytes (HTL) and five cytotoxic T lymphocytes (CTL) epitopes were selected after screening the predicted epitopes for antigenicity, allergenicity, and toxicity. Subsequently, the selected HTL and CTL epitopes were fused via flexible linkers. Next, the cholera toxin B-subunit (CTxB) as an adjuvant was linked to the N-terminal of the chimeric structure. The proposed vaccine was analyzed for the properties of physicochemical, antigenicity, and allergenicity. The 3D model of the vaccine construct was predicted and docked with the Toll-like receptor 4 (TLR4). The molecular dynamics (MD) simulation was performed to evaluate the stable interactions between the vaccine construct and TLR4. The immune simulation was also conducted to explore the immune responses induced by the vaccine. Finally, in silico cloning of the vaccine construct into the pET-28 (+) vector was conducted. The results obtained from all bioinformatics analysis stages were satisfactory; however, in vitro and in vivo tests are essential to validate these results.

Genomic Analysis of Avian Infectious Bronchitis Viruses Recently Isolated in South Korea Reveals Multiple Introductions of GI-19 Lineage (QX Genotype)

Infectious bronchitis virus (IBV) was first identified in the 1930s and it imposes a major economic burden on the poultry industry. In particular, GI-19 lineage has spread globally and has evolved constantly since it was first detected in China. In this study, we analyzed S1 gene sequences from 60 IBVs isolated in South Korea. Two IBV lineages, GI-15 and GI-19, were identified in South Korea. Phylogenetic analysis suggested that there were six distinct subgroups (KM91-like, K40/09-like, and QX-like I to IV) of the South Korean GI-19 IBVs. Among them, QX-type III and IV subgroups, which are phylogenetically different from those reported in South Korea in the past, accounted for more than half of the total. Moreover, the phylogeographic analysis of the QX-like subgroups indicated at least four distinct introductions of GI-19 IBVs into South Korea during 2001–2020. The efficacy of commercialized vaccines against the recently introduced QX-like subgroups should be verified, and continuous international surveillance efforts and quarantine procedures should be enhanced to prevent the incursion of viruses.

S-Acylation of Proteins of Coronavirus and Influenza Virus: Conservation of Acylation Sites in Animal Viruses and DHHC Acyltransferases in Their Animal Reservoirs

Recent pandemics of zoonotic origin were caused by members of coronavirus (CoV) and influenza A (Flu A) viruses. Their glycoproteins (S in CoV, HA in Flu A) and ion channels (E in CoV, M2 in Flu A) are S-acylated. We show that viruses of all genera and from all hosts contain clusters of acylated cysteines in HA, S and E, consistent with the essential function of the modification. In contrast, some Flu viruses lost the acylated cysteine in M2 during evolution, suggesting that it does not affect viral fitness. Members of the DHHC family catalyze palmitoylation. Twenty-three DHHCs exist in humans, but the number varies between vertebrates. SARS-CoV-2 and Flu A proteins are acylated by an overlapping set of DHHCs in human cells. We show that these DHHC genes also exist in other virus hosts. Localization of amino acid substitutions in the 3D structure of DHHCs provided no evidence that their activity or substrate specificity is disturbed. We speculate that newly emerged CoVs or Flu viruses also depend on S-acylation for replication and will use the human DHHCs for that purpose. This feature makes these DHHCs attractive targets for pan-antiviral drugs.

SARS-CoV-2 in animals: From potential hosts to animal models

Within only one year after the first detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), nearly 100 million infections were reported in the human population globally, with more than two million fatal cases. While SARS-CoV-2 most likely originated from a natural wildlife reservoir, neither the immediate viral precursor nor the reservoir or intermediate hosts have been identified conclusively. Due to its zoonotic origin, SARS-CoV-2 may also be relevant to animals. Thus, to evaluate the host range of the virus and to assess the risk to act as potential animal reservoir, a large number of different animal species were experimentally infected with SARS-CoV-2 or monitored in the field in the last months. In this review, we provide an update on studies describing permissive and resistant animal species. Using a scoring system based on viral genome detection subsequent to SARS-CoV-2 inoculation, seroconversion, the development of clinical signs and transmission to conspecifics or humans, the susceptibility of diverse animal species was classified on a semi-quantitative scale. While major livestock species such as pigs, cattle and poultry are mostly resistant, companion animals appear moderately susceptible, while several model animal species used in research, including several Cricetidae species and non-human primates, are highly susceptible to SARS-CoV-2 infection. By natural infections, it became obvious that American minks (Neovison vison) in fur farms, e.g., in the Netherlands and Denmark are highly susceptible resulting in local epidemics in these animals.

Mutations in SARS-CoV-2; Consequences in structure, function, and pathogenicity of the virus

The third pandemic of coronavirus infection, called COVID-19 disease, began recently in China. The newly discovered coronavirus, entitled SARS-CoV-2, is the seventh member of the human coronaviruses. The main pathogenesis of SARS-CoV-2 infection is severe pneumonia, RNAaemia, accompanied by glass turbidity, and acute cardiac injury. It possesses a single-stranded positive-sense RNA genome which is 60–140 nm in diameter, and has a size of 26–32 kbp. Viral pathogenesis is accomplished with spike glycoprotein through the employment of a membrane-bound aminopeptidase, called the ACE2, as its primary cell receptor. It has been confirmed that various factors such as different national rules for quarantine and various races or genetic backgrounds might influence the mortality and infection rate of COVID-19 in the geographic areas. In addition to various known and unknown factors and host genetic susceptibility, mutations and genetic variabilities of the virus itself have a critical impact on variable clinical features of COVID-19. Although the SARS-CoV-2 genome is more stable than SARS-CoV or MERS-CoV, it has a relatively high dynamic mutation rate with respect to other RNA viruses. It's noteworthy that, some mutations can be founder mutations and show specific geographic patterns. Undoubtedly, these mutations can drive viral genetic variability, and because of genotype-phenotype correlation, resulting in a virus with more/lower/no decrease in natural pathogenic fitness or on the other scenario, facilitating their rapid antigenic shifting to escape the host immunity and also inventing a drug resistance virus, so converting it to a more infectious or deadly virus. Overall, the detection of all mutations in SARS-CoV-2 and their relations with pathological changes is nearly impossible, mostly due to asymptomatic subjects. In this review paper, the reported mutations of the SARS-CoV-2 and related variations in virus structure and pathogenicity in different geographic areas and genotypes are widely investigated. Many studies need to be repeated in other regions/locations for other people to confirm the findings. Such studies could benefit patient-specific therapy, according to genotyping patterns of SARS-CoV-2 distribution.

A comprehensive review of SARS-CoV-2 genetic mutations and lessons from animal coronavirus recombination in one health perspective

SARS-CoV-2 was originated from zoonotic coronaviruses and confirmed as a novel beta-coronavirus, which causes serious respiratory illness such as pneumonia and lung failure, COVID-19. In this review, we describe the genetic characteristics of SARS-CoV-2, including types of mutation, and molecular epidemiology, highlighting its key difference from animal coronaviruses. We further summarized the current knowledge on clinical, genetic, and pathological features of several animal coronaviruses and compared them with SARS-CoV-2, as well as recent evidences of interspecies transmission and recombination of animal coronaviruses to provide a better understanding of SARS-CoV-2 infection in One Health perspectives. We also discuss the potential wildlife hosts and zoonotic origin of this emerging virus in detail, that may help mitigate the spread and damages caused by the disease.

Deltacoronavirus Evolution and Transmission: Current Scenario and Evolutionary Perspectives

Deltacoronavirus (DCoV)–the only coronavirus that can infect multiple species of mammals and birds–was initially identified in several avian and mammalian species, including pigs, in China in 2009–2011. Porcine DCoV has since spread worldwide and is associated with multiple outbreaks of diarrheal disease of variable severity in farmed pigs. In contrast, avian DCoV is being reported in wild birds in different countries without any evidence of disease. The DCoV transboundary nature and the recent discovery of its remarkably broad reactivity with its cellular receptor–aminopeptidase N (APN)–from different species emphasize its epidemiological relevance and necessitate additional research. Further, the ability of porcine DCoV to infect and cause disease in chicks and turkey poults and gnotobiotic calves is suggestive of its increased potential for interspecies transmission or of its avian origin. Whether, porcine DCoVs were initially acquired by one or several mammalian species from birds and whether avian and porcine DCoVs continue co-evolving with frequent spillover events remain to be major unanswered questions. In this review, we will discuss the current information on the prevalence, genetic diversity, and pathogenic potential of porcine and avian DCoVs. We will also analyze the existing evidence of the ongoing interspecies transmission of DCoVs that may provide novel insights into their complex evolution.

Investigating the Diversity and Host Range of Novel Parvoviruses from North American Ducks Using Epidemiology, Phylogenetics, Genome Structure, and Codon Usage Analysis

Parvoviruses are small single-stranded DNA viruses that can infect both vertebrates and invertebrates. We report here the full characterization of novel viruses we identified in ducks, including two viral species within the subfamily Hamaparvovirinae (duck-associated chapparvovirus, DAC) and a novel species within the subfamily Densovirinae (duck-associated ambidensovirus, DAAD). Overall, 5.7% and 21.1% of the 123 screened ducks (American black ducks, mallards, northern pintail) were positive for DAC and DAAD, respectively, and both viruses were more frequently detected in autumn than in winter. Genome organization and predicted transcription profiles of DAC and DAAD were similar to viruses of the genera Chaphamaparvovirus and Protoambidensovirus, respectively. Their association to these genera was also demonstrated by subfamily-wide phylogenetic and distance analyses of non-structural protein NS1 sequences. While DACs were included in a highly supported clade of avian viruses, no definitive conclusions could be drawn about the host type of DAAD because it was phylogenetically close to viruses found in vertebrates and invertebrates and analyses of codon usage bias and nucleotide frequencies of viruses within the family Parvoviridae showed no clear host-based viral segregation. This study highlights the high parvoviral diversity in the avian reservoir with many avian-associated parvoviruses likely yet to be discovered.

Similarities and Dissimilarities of COVID-19 and Other Coronavirus Diseases

In less than two decades, three deadly zoonotic coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2, have emerged in humans, causing SARS, MERS, and coronavirus disease 2019 (COVID-19), respectively. The current COVID-19 pandemic poses an unprecedented crisis in health care and social and economic development. It reinforces the cruel fact that CoVs are constantly evolving, possessing the genetic malleability to become highly pathogenic in humans. In this review, we start with an overview of CoV diseases and the molecular virology of CoVs, focusing on similarities and differences between SARS-CoV-2 and its highly pathogenic as well as low-pathogenic counterparts. We then discuss mechanisms underlying pathogenesis and virus-host interactions of SARS-CoV-2 and other CoVs, emphasizing the host immune response. Finally, we summarize strategies adopted for the prevention and treatment of CoV diseases and discuss approaches to develop effective antivirals and vaccines. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Molecular Screening of Salmonella sp. from fecal sample of Sparrows (Passer domesticus) in Yogyakarta, Indonesia

Wild birds is one of the reservoir agent of some of various zoonotic diseases. The study was aim to see the potential of sparrow as the reservoir agent of Salmonella sp. using polymerase chain reaction (PCR) method. We detected the invA gene of Salmonella sp. from faecal sample of sparrows (Passer domesticus) in local area of Yogyakarta, Indonesia. A total of 30 faecal dropping samples were collected from sparrows. DNA was extracted from the faecal samples, then amplified by PCR for the target genes. The amplicons were electrophorized to see the visualization of DNA on the agarose gel. The result showed the prevalence of the positive result of Salmonella sp. was 3,3%. The study indicated that sparrows can spread zoonotic pathogens and this necessitates monitoring for the epidemiologic status of these pathogens among birds, also applying the appropriate intervention measures to prevent the transmission of zoonotic diseasesfrom birds to humans.

Occurrence and Role of Selected RNA-Viruses as Potential Causative Agents of Watery Droppings in Pigeons

The diseases with watery droppings (diarrhea and/or polyuria) can be considered some of the most severe health problems in domestic pigeons of various ages. Although they do not always lead to bird death, they can contribute to poor weight gains and hindered development of young pigeons and, potentially, to poor racing results in sports birds. The gastrointestinal tract disorders of pigeons may be of various etiology, but some of the causative agents are viral infections. This review article provides information collected from scientific reports on RNA-viruses belonging to the Astroviridae, Picornaviridae, and Coronaviridae families; the Avulavirinae subfamily; and the Rotavirus genus that might be implicated in such health problems. It presents a brief characterization, and possible interspecies transmission of these viruses. We believe that this review article will help clinical signs of infection, isolation methods, occurrence in pigeons and poultry, systemize and summarize knowledge on pigeon enteropathogenic viruses and raise awareness of the importance of disease control in pigeons.

Drawing Comparisons between SARS-CoV-2 and the Animal Coronaviruses

The COVID-19 pandemic, caused by a novel zoonotic coronavirus (CoV), SARS-CoV-2, has infected 46,182 million people, resulting in 1,197,026 deaths (as of 1 November 2020), with devastating and far-reaching impacts on economies and societies worldwide. The complex origin, extended human-to-human transmission, pathogenesis, host immune responses, and various clinical presentations of SARS-CoV-2 have presented serious challenges in understanding and combating the pandemic situation. Human CoVs gained attention only after the SARS-CoV outbreak of 2002-2003. On the other hand, animal CoVs have been studied extensively for many decades, providing a plethora of important information on their genetic diversity, transmission, tissue tropism and pathology, host immunity, and therapeutic and prophylactic strategies, some of which have striking resemblance to those seen with SARS-CoV-2. Moreover, the evolution of human CoVs, including SARS-CoV-2, is intermingled with those of animal CoVs. In this comprehensive review, attempts have been made to compare the current knowledge on evolution, transmission, pathogenesis, immunopathology, therapeutics, and prophylaxis of SARS-CoV-2 with those of various animal CoVs. Information on animal CoVs might enhance our understanding of SARS-CoV-2, and accordingly, benefit the development of effective control and prevention strategies against COVID-19.