Detection and molecular characterization of a canine norovirus

Towards Detecting Associations of Canine Astrovirus and Caliciviruses with Health and Living Characteristics of Dogs in Greece

Astroviruses and caliciviruses are important causative agents of gastroenteritis in humans worldwide. They have been detected in a variety of animal species, including dogs, but their role in the induction of disease in animals remains uncertain. In a molecular study that was conducted in Greece, including healthy and gastroenteritis-affected dogs of different ages, astrovirus (AstV) and sapovirus (SaV) were detected in 15% and 26% of the examined animals, respectively. A specialized questionnaire was filled out for each of the dogs participating in the study, including information about different characteristics and risk factors that could possibly affect their health status. This information was analyzed with the use of two innovative statistical methods, i.e., a Multiple Correspondence Analysis (MCA) and the Ascending Hierarchical Classification (AHC). Based on their results, it was possible to define various groups of dogs based on their characteristics. AstV seems to occur more often in low-health-status dogs, usually mongrels, living in rural areas, showing vomit, diarrhea, and diet changes. Dogs of this group usually live with other pets in the same household and have frequent contact with stray animals. The presence of SaV does not seem to be associated with any of the examined factors.

Establishment of a Quadruplex RT-qPCR for the Detection of Canine Coronavirus, Canine Respiratory Coronavirus, Canine Adenovirus Type 2, and Canine Norovirus

Canine coronavirus (CCoV), canine respiratory coronavirus (CRCoV), canine adenovirus type 2 (CAV-2), and canine norovirus (CNV) are important pathogens for canine viral gastrointestinal and respiratory diseases. Especially, co-infections with these viruses exacerbate the damages of diseases. In this study, four pairs of primers and probes were designed to specifically amplify the conserved regions of the CCoV M gene, CRCoV N gene, CAV-2 hexon gene, and CNV RdRp gene. After optimizing different reaction conditions, a quadruplex RT-qPCR was established for the detection of CCoV, CRCoV, CAV-2, and CNV. The specificity, sensitivity, and repeatability of the established assay were evaluated. Then, the assay was used to test 1688 clinical samples from pet hospitals in Guangxi province of China during 2022-2024 to validate its clinical applicability. In addition, these samples were also assessed using the reported reference RT-qPCR assays, and the agreements between the developed and reference assays were determined. The results indicated that the quadruplex RT-qPCR could specifically test only CCoV, CRCoV, CAV-2, and CNV, without cross-reaction with other canine viruses. The assay had high sensitivity with limits of detection (LODs) of 1.0 × 102 copies/reaction for CCoV, CRCoV, CAV-2, and CNV. The repeatability was excellent, with intra-assay variability of 0.19-1.31% and inter-assay variability of 0.10-0.88%. The positivity rates of CCoV, CRCoV, CAV-2, and CNV using the developed assay were 8.59% (145/1688), 8.65% (146/1688), 2.84% (48/1688), and 1.30% (22/1688), respectively, while the positivity rates using the reference assays were 8.47% (143/1688), 8.53% (144/1688), 2.78% (47/1688), and 1.24% (21/1688), respectively, with agreements of more than 99.53% between two methods. In conclusion, a quadruplex RT-qPCR with high sensitivity, specificity, and repeatability was developed for rapid, and accurate detection of CCoV, CRCoV, CAV-2, and CNV.

Analysis of viral diversity in dogs with acute gastroenteritis from Brazilian Amazon

Viral gastroenteritis is commonly reported in dogs and involves a great diversity of enteric viruses. In this research, viral diversity was investigated in dogs with diarrhea in Northern Brazil using shotgun metagenomics. Furthermore, the presence of norovirus (NoV) was investigated in 282 stool/rectal swabs of young/adult dogs with or without diarrhea from two public kennels, based on one-step reverse transcription polymerase chain reaction (RT-PCR) for genogroup VI and VII (GVI and GVII) and real-time RT-PCR for GI, GII, and GIV. Thirty-one viral families were identified, including bacteriophages. Phylogenetic analyses showed twelve complete or nearly complete genomes belonging to the species of Protoparvovirus carnivoran1, Mamastrovirus 5, Aichivirus A2, Alphacoronavirus 1, and Chipapillomavirus 1. This is the first description of the intestinal virome of dogs in Northern Brazil and the first detection of canine norovirus GVII in the country. These results are important for helping to understand the viral groups that circulate in the canine population.

Genetic detection and analysis of porcine norovirus in pigs farmed in north Vietnam

Norovirus (NoV) causing gastroenteritis symptoms, which has been reported in several hosts, including humans, pigs, and rats. This study was conducted to identify porcine viral infection and to characterize NoV strains from pigs in some provinces in north Vietnam. Totally, 102 fecal samples from diarrheal pigs on farms in six cities and provinces in northern Vietnam during July 2022 to March 2023 were collected. Polymerase chain reaction was used to identify the viral genome. Positive samples were used for nucleotide sequencing of the partial RNA-dependent RNA polymerase gene sequence. Five (4.9 %) positive stool samples were detected from animals farmed in five different farms, with one positive animal identified in each farm. Genetic analysis indicated that nucleotide identity was in the range 97.77-99.62 % among the 5 NoVs in this study. Phylogenetic analysis pointed out that the five NoVs were Genotype II.19 viruses. Genetically, these strains were closely related to porcine NoV strains that were reported in China in 2009.

Molecular characterization of norovirus and sapovirus detected in animals and humans in Costa Rica: Zoo-anthropozoonotic potential of human norovirus GII.4

Background

Noroviruses (NoV) and sapoviruses (SaV) are major causes of acute viral gastroenteritis in humans worldwide, as well as gastrointestinal infections in animals. However, it has not been determined whether these viruses are zoonotic pathogens.

Aim

In this study, we investigated the presence of NoV and SaV in stool samples from dogs, pigs, cows, and humans to determine some aspects of the molecular epidemiology and the genetic relationship of several strains present in these species.

Methods

Polymerase chain reaction and sequencing of NoV and SaV strains present in stool samples from humans and dogs with diarrhea, pigs, and cattle with and without diarrhea were carried out during fragmented periods from 2002 to 2012.

Results

Of all samples analyzed, 11.6% (123/1,061) of the samples were positive for NoV and 0.88% (9/1,023) were positive for SaV. The phylogenetic analysis confirmed 16 human strains of NoV (HuNoV) belonging to HuNoV G?/GII.P2 (1), GII.4/GII.P4 (5), G?/GII.P4 (9), and GII.6/GII.P6 (1) and allowed us to verify and assign three strains of human SaV to genotypes GI.2 (1) and GII.5 (2). In dogs, eight strains of NoV [HuNoV G?/GII.P4 (4) and canine G?/GVI.P1 (4)] and two strains of canine SaV were determined. In pigs, six strains were assigned to HuNoV G?/GII.P4 and four strains to porcine SaV were assigned to genogroup GIII (2), GVIII (1), and GXI (1). In bovines, five strains were characterized as HuNoV G?/GII.P4.

Conclusions

This study showed that NoV and SaV prototype strains have been present in humans and dogs in Costa Rica. Additionally, it revealed that the zoonotic potential of SaV is very limited, while the zoonotic implications for HuNoV GII.4 are stronger due to the simultaneous circulation of strains related to HuNoV GII.4 in four species, which suggests a zoo-anthropozoonosis.

First report of canine Astrovirus and Sapovirus in Greece, hosting both asymptomatic and gastroenteritis symptomatic dogs

Background

Astrovirus, Norovirus and Sapovirus are widely distributed viruses in humans and animals worldwide. They have frequently been associated with disease, mainly of gastroenteric nature. In dogs, these viruses have been detected both in symptomatic and asymptomatic animals, mainly of young age.

Methods

In the present epidemiologic study, we investigated the presence of canine Astrovirus (CAstV), canine Norovirus (canine NoV) and canine Sapovirus (Canine SaV) in saliva and stools of 201 domestic dogs originating from throughout Greece, based on two different molecular methods, i.e. conventional and SYBR-Green Real-time RT-PCR. The samples derived from young and adult asymptomatic and symptomatic animals. CAstV was detected in 15/201 (7.5%) and 29/201 (15%) of the examined dogs using conventional RT-PCR and SYBR-Green Real time RT-PCR, respectively.

Results

The prevalence of the virus was higher at healthy dogs, with a slight discrepancy of the two methods on the aspect of age (67% young dogs with the method of conventional RT-PCR, versus 52% adult positive dogs with the method of SYBR-Green Real-time RT-PCR). Canine SaV was detected in 52/201 (23%) of the dogs (mainly young and asymptomatic), with the method of SYBR-Green Real-time RT-PCR only, while canine NoV was not detected in any sample with either of the two methods applied. Sequencing of the CAstV positive samples resulted in the acquisition of one CAstV sequence. Phylogenetic analysis confirmed the results, clustering the CAstV sequence with homologous canine hosting sequences from other countries.

Conclusions

CAstV and Canine SaV were proved to circulate in Greek dogs. SYBR-Green Real time RT-PCR showed greater sensitivity in the detection of these viruses. Additionally, we were able to specify the CAstV strain that circulates in Greece, through phylogenetic analysis. To our knowledge, this is the first epidemiological study of CAstV and canine SaV in dogs in Greece, as well as the first time detected in dogs from Greece.

Investigation and analysis on an outbreak of norovirus infection in a health school in Guangdong Province, China

Our objective was to describe the epidemiological features of an outbreak of norovirus infection in a health school in Guangdong province, China, to identify the cause of such a large scale outbreak of norovirus among older students, to simulate the transmission dynamics, and to evaluate the effect of intervention measures of GII.17 [P17] genotype norovirus infection. We identified all cases during the outbreak. Descriptive epidemiological, analytical epidemiological and hygiene survey methods were used to described the outbreak epidemic course and identify the cause of the outbreak of norovirus infection. We also used dynamical model to simulate the transmission dynamics of norovirus infection and evaluate the effect of intervention measures. Norovirus genotyping was assigned to the newly obtained strains, with a maximum likelihood phylogenetic analysis conducted. There were 360 cases of 42 classes in five grades with a 12.99% attack rate. Proportionally, more students were in contact with sick students and vomit in the suspected case group than the control group (χ² = 5.535, P = 0.019 and χ² = 5.549, P = 0.019, respectively). The basic reproduction number was 8.32 before and 0.49 after the intervention. Dynamical modeling showed that if the isolation rate was higher or case isolation began earlier, the total attack rate would decrease. Molecular characterization identified the GII.17 [P17] genotype in all stains obtained from the health school, which were clustered with high support in the phylogenetic tree. This was an outbreak of norovirus infection caused by contact transmission. The main reasons for the spread of the epidemic were the later control time, irregular treatment of vomit and no case isolation. The transmission dynamics of contact transmission was high, more efficient control measures should be employed.

First detection of canine norovirus in dogs and a complete GVI.2 genome in mainland China

Canine norovirus (CNV) is a diarrhea-causing pathogen in canines. In this study, 268 canine diarrheic fecal samples were collected from 13 pet hospitals across three provinces in China between March 2017 and May 2019, and 7.8% (21/268) samples were detected as CNV-positive by RT-PCR. Phylogenetic analysis of twenty-one CNV RdRp fragments showed that eighteen of the strains clustered in GVI.2, two clustered in GVI.1 and one clustered in GIV.2. The complete RdRp, VP1, and VP2 genes of four GVI.2 strains obtained from three provinces were successfully sequenced. Phylogenetic analyses based on the RdRp, VP1, and VP2 genes showed that the GVI.2 strains from this study were closely related to USA GVI.2 strains. The complete genome of GVI.2 strain Dog/M9/18/CH was successfully sequenced, it was 7905 nucleotides (nt) in length and shared 95.9% nt identity with the sole available, nearly full-length genome of GVI.2 strain genome. To our knowledge, this is first description of the molecular prevalence of CNV in mainland China, and the first report of a complete GVI.2 genome. These findings will extend our understanding of epidemics and the genetic evolution of CNV.

Human Norovirus Infection in Dogs, Thailand

In July 2018, recombinant norovirus GII.Pe-GII.4 Sydney was detected in dogs who had diarrhea in a kennel and in children living on the same premises in Thailand. Whole-genome sequencing and phylogenetic analysis of 4 noroviruses from Thailand showed that the canine norovirus was closely related to human norovirus GII.Pe-GII.4 Sydney, suggesting human-to-canine transmission.

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.

Emergence of norovirus strains: A tale of two genes

Noroviruses are a very diverse group of viruses that infect different mammalian species. In humans, norovirus is a major cause of acute gastroenteritis. Multiple norovirus infections can occur in a lifetime as the result of limited duration of acquired immunity and cross-protection among different strains. A combination of advances in sequencing methods and improvements on surveillance has provided new insights into norovirus diversification and emergence. The generation of diverse norovirus strains has been associated with (1) point mutations on two different genes: ORF1, encoding the non-structural proteins, and ORF2, encoding the major capsid protein (VP1); and (2) recombination events that create chimeric viruses. While both mechanisms are exploited by all norovirus strains, individual genotypes utilize each mechanism differently to emerge and persist in the human population. GII.4 noroviruses (the most prevalent genotype in humans) present an accumulation of amino acid mutations on VP1 resulting in the chronological emergence of new variants. In contrast, non-GII.4 noroviruses present co-circulation of different variants over long periods with limited changes on their VP1. Notably, genetic diversity of non-GII.4 noroviruses is mostly related to the high number of recombinant strains detected in humans. While it is difficult to determine the precise mechanism of emergence of epidemic noroviruses, observations point to multiple factors that include host-virus interactions and changes on two regions of the genome (ORF1 and ORF2). Larger datasets of viral genomes are needed to facilitate comparison of epidemic strains and those circulating at low levels in the population. This will provide a better understanding of the mechanism of norovirus emergence and persistence.

Feline Virome-A Review of Novel Enteric Viruses Detected in Cats

Recent advances in the diagnostic and metagenomic investigations of the feline enteric environment have allowed the identification of several novel viruses that have been associated with gastroenteritis in cats. In the last few years, noroviruses, kobuviruses, and novel parvoviruses have been repetitively detected in diarrheic cats as alone or in mixed infections with other pathogens, raising a number of questions, with particular regards to their pathogenic attitude and clinical impact. In the present article, the current available literature on novel potential feline enteric viruses is reviewed, providing a meaningful update on the etiology, epidemiologic, pathogenetic, clinical, and diagnostic aspects of the infections caused by these pathogens.

Faecal Virome Analysis of Wild Animals from Brazil

The Brazilian Cerrado fauna shows very wide diversity and can be a potential viral reservoir. Therefore, the animal's susceptibility to some virus can serve as early warning signs of potential human virus diseases. Moreover, the wild animal virome of this biome is unknown. Based on this scenario, high-throughput sequencing contributes a robust tool for the identification of known and unknown virus species in this environment. In the present study, faeces samples from cerrado birds (Psittacara leucophthalmus, Amazona aestiva, and Sicalis flaveola) and mammals (Didelphis albiventris, Sapajus libidinosus, and Galictis cuja) were collected at the Veterinary Hospital, University of Brasília. Viral nucleic acid was extracted, submitted to random amplification, and sequenced by Illumina HiSeq platform. The reads were de novo assembled, and the identities of the contigs were evaluated by Blastn and tblastx searches. Most viral contigs analyzed were closely related to bacteriophages. Novel archaeal viruses of the Smacoviridae family were detected. Moreover, sequences of members of Adenoviridae, Anelloviridae, Circoviridae, Caliciviridae, and Parvoviridae families were identified. Complete and nearly complete genomes of known anelloviruses, circoviruses, and parvoviruses were obtained, as well as putative novel species. We demonstrate that the metagenomics approach applied in this work was effective for identification of known and putative new viruses in faeces samples from Brazilian Cerrado fauna.

Norovirus Attachment and Entry

Human norovirus is a major human pathogen causing the majority of cases of viral gastroenteritis globally. Viral entry is the first step of the viral life cycle and is a significant determinant of cell tropism, host range, immune interactions, and pathogenesis. Bile salts and histo-blood group antigens are key mediators of norovirus entry; however, the molecular mechanisms by which these molecules promote infection and the identity of a potential human norovirus receptor remain unknown. Recently, there have been several important advances in norovirus entry biology including the identification of CD300lf as the receptor for murine norovirus and of the role of the minor capsid protein VP2 in viral genome release. Here, we will review the current understanding about norovirus attachment and entry and highlight important future directions.

The Microtubule-Associated Innate Immune Sensor GEF-H1 Does Not Influence Mouse Norovirus Replication in Murine Macrophages

Norovirus is an acute infection of the gastrointestinal tract causing rapid induction of vomiting and diarrhoea. The infection is sensed and controlled by the innate immune system, particularly by the RNA helicase MDA-5 and type I and III interferons (IFNs). We have observed that intracellular replication of murine norovirus (MNV) occurs in membranous clusters proximal to the microtubule organising centre, a localisation dependent on intact microtubules. Recently, it was shown that the host protein guanine nucleotide exchange factor-H1 (GEF-H1) is a microtubule-associated innate immune sensor that activates interferon Regulatory Factor 3 to induce the production of type I IFNs. Thus, we interrogated the potential role of GEF-H1 in controlling MNV infections. We observed that GEF-H1 was recruited to the MNV replication complex; however RNAi-mediated suppression of GEF-H1 did not outwardly affect replication. We furthered our studies to investigate the impact of GEF-H1 on MNV innate detection and observed that GEF-H1 did not contribute to type I IFN induction during MNV infection or influenza virus infection but did result in a small reduction of interferon–β (IFNβ) during West Nile virus infection. Intriguingly, we discovered an interaction of GEF-H1 with the viral MNV non-structural protein 3 (NS3), an interaction that altered the location of GEF-H1 within the cell and prevented the formation of GEF-H1-induced microtubule fibres. Thus, our results indicate that GEF-H1 does not contribute significantly to the innate immune sensing of MNV, although its function may be modulated via interaction with the viral NS3 protein.

Identification of canine norovirus in dogs in South Korea

Background

Canine noroviruses (CaNoVs) are classified into genogroups GIV, GVI, and GVII and have been detected in fecal samples from dogs since their first appearance in a dog with enteritis in Italy in 2007. CaNoVs may be a public health concern because pet animals are an integral part of the family and could be a potential reservoir of zoonotic agents. Nonetheless, there was no previous information concerning the epidemiology of CaNoV in South Korea. In the present study, we aimed to detect CaNoV antigens and to investigate serological response against CaNoV in dogs.

Results

In total, 459 fecal samples and 427 sera were collected from small animal clinics and animal shelters housing free-roaming dogs in geographically distinct areas in South Korea. For the detection of CaNoV, RT-PCR was performed using target specific primers, and nucleotide sequences of CaNoV isolates were phylogenetically analyzed. Seroprevalence was performed by ELISA based on P domain protein. CaNoVs were detected in dog fecal samples (14/459, 3.1%) and were phylogenetically classified into the same cluster as previously reported genogroup GIV CaNoVs. Seroprevalence was performed, and 68 (15.9%) of 427 total dog serum samples tested positive for CaNoV IgG antibodies.

Conclusion

This is the first study identifying CaNoV in the South Korean dog population.

A semi-nested RT-PCR assay for detection of norovirus in rat fecal samples

Norovirus is a highly prevalent pathogen that can infect a wide range of host species. Thus far, there have only been two reports of norovirus infection in rats. Diagnostic assays for the detection of norovirus are well established, but a specific molecular assay for the diagnosis of norovirus infection in laboratory rats has not yet been reported. In this study, we describe the development of a sensitive, semi-nested RT-PCR assay for detection of norovirus in fecal samples from Rattus norvegicus, reared in animal facilities under different sanitary barrier conditions. Additionally, we describe the first report of the presence of norovirus in rat colonies from Brazilian animal facilities.

Recombinant GII.P16/GII.4 Sydney 2012 Was the Dominant Norovirus Identified in Australia and New Zealand in 2017

For the past two decades, norovirus pandemic variants have emerged every 3–5 years, and dominate until they are replaced by alternate strains. However, this scenario changed in 2016 with the co-circulation of six prevalent viruses, three of which possessed the pandemic GII.4 Sydney 2012 capsid. An increased number of institutional gastroenteritis outbreaks were reported within the Oceania region in mid-2017. This study identified emerging noroviruses circulating in Australia and New Zealand in 2017 to assess the changing dynamics of the virus infection. RT-PCR-based methods, next generation sequencing, and phylogenetic analyses were used to genotype noroviruses from both clinical and wastewater samples. Antigenic changes were observed between the capsid of pandemic Sydney 2012 variant and the two new Sydney recombinant viruses. The combination of these antigenic changes and the acquisition of a new ORF1 through recombination could both facilitate their ongoing persistence in the population. Overall, an increased prevalence of GII.P16/GII.4 Sydney 2012 viruses was observed in 2017, replacing the GII.P16/GII.2 recombinant that dominated in the region at the end of 2016. This shift in strain dominance was also observed in wastewater samples, demonstrating the reliability of wastewater as a molecular surveillance tool.

Human noroviruses in the faeces of wild birds and rodents-new potential transmission routes

Human noroviruses (HuNoVs) are one of the leading global causes of diarrhoeal diseases and are transmitted mainly from person to person but also through contaminated food, water and fomites. The possible zoonotic nature of NoVs has occasionally been discussed, although the viruses are generally considered to be host-species-specific. We investigated whether wild birds and rodents could serve as carriers of HuNoVs, thereby transmitting the virus to humans directly or indirectly by contaminating foods. All samples, 115 avian and 100 rat faeces collected in springs 2009-2013 from dump sites, and 85 faeces from yellow-necked mice trapped in late autumn 2008 and 2009 after the rodents entered human settlements due to the first night frosts, were screened for HuNoV using real-time reverse transcription PCR. HuNoVs were detected in 31 (27%) faecal samples of wild birds, in two (2%) faecal samples of rats and in no samples of mice. Most (25) of the positive bird samples and both rat samples contained genogroup II, and six positive bird samples contained genogroup I HuNoV. The avian species shedding faeces containing HuNoVs were identified as gulls and crows using DNA barcoding. Our results show that wildlife, birds and rats in particular, is capable of spreading HuNoVs in the environment.

New viruses associated with canine gastroenteritis

A number of novel viruses have been associated with canine gastroenteritis in recent years, from viral families as diverse as Caliciviridae and Picornaviridae to Parvoviridae and Circoviridae. The ability of many of these viruses to cause disease is uncertain, but epidemiological studies are continually adding to our knowledge of these potential pathogens. This review presents a summary of the latest research and current understanding of novel viruses associated with canine gastroenteritis.

RNA Sequencing of Murine Norovirus-Infected Cells Reveals Transcriptional Alteration of Genes Important to Viral Recognition and Antigen Presentation

Viruses inherently exploit normal cellular functions to promote replication and survival. One mechanism involves transcriptional control of the host, and knowledge of the genes modified and their molecular function can aid in understanding viral-host interactions. Norovirus pathogenesis, despite the recent advances in cell cultivation, remains largely uncharacterized. Several studies have utilized the related murine norovirus (MNV) to identify innate response, antigen presentation, and cellular recognition components that are activated during infection. In this study, we have used next-generation sequencing to probe the transcriptomic changes of MNV-infected mouse macrophages. Our in-depth analysis has revealed that MNV is a potent stimulator of the innate response including genes involved in interferon and cytokine production pathways. We observed that genes involved in viral recognition, namely IFIH1, DDX58, and DHX58 were significantly upregulated with infection, whereas we observed significant downregulation of cytokine receptors (Il17rc, Il1rl1, Cxcr3, and Cxcr5) and TLR7. Furthermore, we identified that pathways involved in protein degradation (including genes Psmb3, Psmb4, Psmb5, Psmb9, and Psme2), antigen presentation, and lymphocyte activation are downregulated by MNV infection. Thus, our findings illustrate that MNV induces perturbations in the innate immune transcriptome, particularly in MHC maturation and viral recognition that can contribute to disease pathogenesis.

Frequency and molecular characterization of human norovirus in Erzurum, Turkey

BACKGROUND/AIM

There are limited studies on genotyping and phylogenetic analysis of norovirus in Turkey, and this has not previously been studied in the Eastern Anatolia region. The aim of the present study was to determine the norovirus profile in this region with genotyping and phylogenetic analysis.

MATERIALS AND METHODS

Included in the study were stool samples obtained from 427 people from different age groups in Eastern Anatolia. The nucleic acid samples isolated by the automatic system and nucleic acid sequence reactions and phylogenetic analyses were performed on RNA samples.

RESULTS

The presence of norovirus was detected in 86 (20.1%) of the 427 stool samples by RT-PCR analysis. Twenty-six samples selected randomly from norovirus-RNA positive samples were subjected to the sequence reaction. In 24 of the 26 samples, genogroup GII was determined, as well as one each from GI and GIV in sequence reactions. Four different genotypes were detected in genogroup GII, which were determined to be the dominant types. These were GII.1, GII.4, GII.16, and GII.21. The GI.6 and GIV.1 genotypes were determined in genogroups GI and GIV, respectively.

CONCLUSION

The high frequency and genetic diversity of these infections are risk factors for disease and so vaccine studies should be undertaken in consideration of this situation.

Seroprevalence for norovirus genogroup II, IV and VI in dogs

Molecular and serological data suggest that noroviruses (NoVs) might be transmitted between humans and domestic carnivores. In this study we screened an age-stratified collection of canine sera (n=516) by using an ELISA assay based on virus-like particles (VLPs) of human NoVs GII.4 and GIV.1 and carnivore NoVs GIV.2 and GVI.2. Antibodies against GII.4 and GIV.1 human NoVs and GIV.2 and GVI.2 NoVs from carnivores were identified in dog sera (13.0%, 67/516) suggesting their exposure to homologous and heterologous NoVs. Analysis of the trends of age-class prevalence showed a gradual increase in the positive rate from 9.0% and 7.0%, in young dogs <1year of age to 15.0% in dogs older than 12 years, for GII.4 and GVI.2 NoVs, respectively. A significant difference in the IgG distribution by age classes was observed for GIV.1 NoVs, with the highest rate of antibodies (7.0%) in the age group <1year and the lowest (1.0%) in the age-classes 7-9 (P=0.049). High correlation between the reactivity to GII.4 and GVI.2 NoVs was observed, likely due to conserved epitopes in the capsid structure.

Identification of a novel canine norovirus

By screening a collection of fecal samples from young dogs from different European countries, noroviruses (NoVs) were found in 13/294 (4.4%) animals with signs of enteritis whilst they were not detected in healthy dogs (0/42). An informative portion of the genome (3.4 kb at the 3′ end) was generated for four NoV strains. In the capsid protein VP1 region, strains 63.15/2015/ITA and FD53/2007/ITA were genetically related to the canine GVI.2 strain C33/Viseu/2007/PRT (97.4–98.6% nt and 90.3–98.6% aa). Strain FD210/2007/ITA displayed the highest identity to the GVI.1 canine strain Bari/91/2007/ITA (88.0% nt and 95.0% aa). Strain 5010/2009/ITA displayed only 66.6–67.6% nt and 75.5–81.6% aa identities to the GVI.1 canine strains FD210/2007/ITA and Bari/91/2007/ITA and the GVI feline strain M49-1/2012/JPN. Identity to the other canine/feline NoVs strains in the VP1 was lower than 67.6% nt and 62.7% aa. Based on the full-length VP1 amino acid sequence and the criteria proposed for distinction of NoV genotypes, the canine NoV 5010/2009/ITA could represent the prototype of a third GVI genotype, thus providing further evidence for the genetic heterogeneity of NoVs in carnivores.

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Noroviruses are important human pathogens, also found in several animal species.

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Canine noroviruses were detected in 4.4% (13/294) of diarrhoeic dogs.

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Upon genome sequencing, a novel canine norovirus was identified.

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The observed genetic diversity may pose a challenge for diagnostics.

A molecular survey for selected viral enteropathogens revealed a limited role of Canine circovirus in the development of canine acute gastroenteritis

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A molecular survey for selected viral enteropathogens was conducted in dogs with and without acute gastroenteritis.

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Canine parvovirus and coronavirus were strongly associated with occurrence of enteric disease.

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Canine circovirus infections correlated with acute gastroenteritis only when associated with other enteric viruses.

Canine circovirus (CanineCV) is a canine virus, whose pathogenetic role is still uncertain. Based on recent data suggesting its role as entheropathogen, a case-control study was conducted between 2013 and 2016 to investigate the association of CanineCV with gastroenteritis in dogs, alone or in combination with other viral pathogens, including canine parvovirus (CPV), canine coronavirus (CCoV) and canine distemper virus (CDV). A total of 219 dogs suffering from acute gastroenteritis disorders and 67 controls randomly recruited among healthy dogs or patients presenting without enteric signs were screened by a panel of real-time (RT-)PCR assays for CanineCV, CPV, CCoV and CDV. A high prevalence of viral infections was detected in dogs with gastroenteritis (77.16%), with CPV representing the most frequently detected enteropathogen, followed by CanineCV and CCoV. While CPV and CCoV infections displayed a strong association with occurrence of acute gastroenteritis (p < 0.00001), detection of CanineCV in control dogs (28.35%) occurred with prevalence comparable to that of clinical cases (32.42%), so that its correlation with gastrointestinal disease was not statistically supported (p = 0.530988). Different from the clinical cases, where co-infections were frequently observed, all positive samples from the control group contained single infections. Noteworthy, a significant association was calculated between co-infections with CanineCV and occurrence of acute gastroenteritis (p < 0.00001). This study supports the role of CanineCV as a co-pathogen in the development of gastrointestinal disease, mainly acting in synergism with other enteric viruses.

[Discovery of murine norovirus receptor]

Norovirus is the leading cause of acute gastroenteritis worldwide. Since the discovery of human norovirus (HuNoV), an efficient and reproducible norovirus replication system has not been established in cultured cells. Although limited amounts of virus particles can be produced when the HuNoV genome is directly transfected into cells, the HuNoV cycle of infection has not been successfully reproduced in any currently available cell-culture system. Those results imply that the identification of a functional cell-surface receptor for norovirus might be the key to establishing a norovirus culture system. Using a genome-wide CRISPR/Cas9 guide RNA library, we identified murine CD300lf and CD300ld as functional receptors for murine norovirus (MNV). The treatment of susceptible cells with polyclonal antibody against CD300lf significantly reduced the production of viral progeny. Additionally, ectopic CD300lf expression in nonsusceptible cell lines derived from other animal species enabled MNV infection and progeny production, suggesting that CD300lf has potential for dictating MNV host tropism. Furthermore, CD300ld, which has an amino acid sequence in the N-terminal region of its extracellular domain that is highly homologous to that of CD300lf, also functions as a receptor for MNV. Our results indicate that direct interaction of MNV with two cell-surface molecules, CD300lf and CD300ld, dictates permissive noroviral infection.

Murine norovirus infection in Brazilian animal facilities

Murine norovirus (MNV) is a single-stranded positive-sense RNA virus of the Caliciviridae family. MNV has been reported to infect laboratory mice with the ability to cause lethal infections in strains lacking components of the innate immune response. Currently, MNV is considered the most prevalent infectious agent detected in laboratory mouse facilities. In this study, mice in 22 laboratory animal facilities within Brazil were analyzed for MNV infection. Using primers targeting a conserved region of the viral capsid, MNV was detected by RT-PCR in 137 of 359 mice from all 22 facilities. Nucleotide sequencing and phylogenetic analysis of the capsid region from the viral genome showed identity ranging from 87% to 99% when compared to reported MNV sequences. In addition, RAW264.7 cells inoculated with a mouse fecal suspension displayed cytopathic effect after the fifth passage. This study represents the first report of MNV in mouse colonies in Brazilian laboratory animal facilities, emphasizing the relevance of a health surveillance program in such environments.

Divergent Sapovirus Strains and Infection Prevalence in Wild Carnivores in the Serengeti Ecosystem: A Long-Term Study

The genus Sapovirus, in the family Caliciviridae, includes enteric viruses of humans and domestic animals. Information on sapovirus infection of wildlife is limited and is currently lacking for any free-ranging wildlife species in Africa. By screening a large number of predominantly fecal samples (n = 631) obtained from five carnivore species in the Serengeti ecosystem, East Africa, sapovirus RNA was detected in the spotted hyena (Crocuta crocuta, family Hyaenidae), African lion (Panthera leo, family Felidae), and bat-eared fox (Otocyon megalotis, family Canidae), but not in golden or silver-backed jackals (Canis aureus and C. mesomelas, respectively, family Canidae). A phylogenetic analysis based on partial RNA-dependent RNA polymerase (RdRp) gene sequences placed the sapovirus strains from African carnivores in a monophyletic group. Within this monophyletic group, sapovirus strains from spotted hyenas formed one independent sub-group, and those from bat-eared fox and African lion a second sub-group. The percentage nucleotide similarity between sapoviruses from African carnivores and those from other species was low (< 70.4%). Long-term monitoring of sapovirus in a population of individually known spotted hyenas from 2001 to 2012 revealed: i) a relatively high overall infection prevalence (34.8%); ii) the circulation of several genetically diverse variants; iii) large fluctuations in infection prevalence across years, indicative of outbreaks; iv) no significant difference in the likelihood of infection between animals in different age categories. The likelihood of sapovirus infection decreased with increasing hyena group size, suggesting an encounter reduction effect, but was independent of socially mediated ano-genital contact, or the extent of the area over which an individual roamed.

Genetically distinct genogroup IV norovirus strains identified in wastewater

We investigated the prevalence and genetic diversity of genogroup IV norovirus (GIV NoV) strains in wastewater in Arizona, United States, over a 13-month period. Among 50 wastewater samples tested, GIV NoVs were identified in 13 (26 %) of the samples. A total of 47 different GIV NoV strains were identified, which were classified into two genetically distinct clusters: the GIV.1 human cluster and a unique genetic cluster closely related to strains previously identified in Japanese wastewater. The results provide additional evidence of the considerable genetic diversity among GIV NoV strains through the analysis of wastewater containing virus strains shed from all populations.

Human and Animal Viruses in Food (Including Taxonomy of Enteric Viruses)

In recent years, there has been an increase in the incidence of foodborne diseases worldwide, with viruses now being recognized as a major cause of these illnesses. The most common viruses implicated in foodborne disease are enteric viruses, which are found in the human gastrointestinal tract, excreted in human feces and transmitted by the fecal-oral route. Many different viruses are found in the gastrointestinal tract but not all are recognized as foodborne pathogens. The diseases caused by enteric viruses fall into three main types: gastroenteritis, enterically transmitted hepatitis, and illnesses that can affect other parts of the body such as the eye, the respiratory system and the central nervous system leading to conjunctivitis, poliomyelitis, meningitis and encephalitis. Viral pathogens excreted in human feces include noroviruses, sapoviruses, enteroviruses, adenoviruses, hepatitis A virus (HAV), hepatitis E virus (HEV), rotaviruses, and astroviruses. Most of these viruses have been associated with foodborne disease outbreaks. Noroviruses and HAV are commonly identified as foodborne causes of gastroenteritis and acute hepatitis, respectively.

Prevalence and molecular characterization of human noroviruses and sapoviruses in Ethiopia

Viral gastroenteritis is a major public health problem worldwide. In Ethiopia, very limited studies have been done on the epidemiology of enteropathogenic viruses. The aim of this study was to detect and characterize noroviruses (NoVs) and sapoviruses (SaVs) from acute gastroenteritis patients of all ages. Fecal samples were collected from diarrheic patients (n = 213) in five different health centers in Addis Ababa during June-September 2013. The samples were screened for caliciviruses by reverse transcription polymerase chain reaction (RT-PCR) using universal and genogroup-specific primer pairs. Phylogenetic analyses were conducted using the sequences of the PCR products. Of the clinical samples, 25.3 % and 4.2 % were positive for NoV and SaV RNA, respectively. Among the norovirus positives, 22 were sequenced further, and diverse norovirus strains were identified: GI (n = 4), GII (n = 17) and GIV (n = 1). Most strains were GII (n = 17/22: 77.2 %), which were further divided into three different genotypes (GII.4, GII.12/GII.g recombinant-like and GII.17), with GII.17 being the dominant (7/17) strain detected. GI noroviruses, in particular GI.4 (n = 1), GI.5 (n = 2) and GI.8 (n = 1), were also detected and characterized. The GIV strain detected is the first from East Africa. The sapoviruses sequenced were also the first reported from Ethiopia. Collectively, this study showed the high burden and diversity of noroviruses and circulation of sapoviruses in diarrheic patients in Ethiopia. Continued surveillance to assess their association with diarrhea is needed to define their epidemiology, disease burden, and impact on public health.

Molecular Diagnostic Methods for Detection and Characterization of Human Noroviruses

Human noroviruses are a group of viral agents that afflict people of all age groups. The viruses are now recognized as the most common causative agent of nonbacterial acute gastroenteritis and foodborne viral illness worldwide. However, they have been considered to play insignificant roles in the disease burden of acute gastroenteritis for the past decades until the recent advent of new and more sensitive molecular diagnostic methods. The availability and application of the molecular diagnostic methods have led to enhanced detection of noroviruses in clinical, food and environmental samples, significantly increasing the recognition of noroviruses as an etiologic agent of epidemic and sporadic acute gastroenteritis. This article aims to summarize recent efforts made for the development of molecular methods for the detection and characterization of human noroviruses.

Detection of Norovirus and Sapovirus from diarrheic dogs and cats in Japan

Norovirus (NoV) and sapovirus (SaV) are important causes of human diarrhea. In this study, between 2007 and 2014 fecal samples were collected from 97 dogs and 83 cats with diarrhea and examined to determine the prevalence of NoV and SaV infections in Japan. To detect caliciviruses, approximately 300 bases targeting the polymerase gene were amplified using RT-PCR and subjected to phylogenetic and homology analyses. Specific PCR products were obtained from four canine and nine feline samples: two canine and one feline isolate were classified as NoV, two canine isolates as SaV and the remaining eight feline isolates as vesivirus (VeV). The three NoV isolates were classified into the same clade as that of known canine and feline NoVs; their homologies (75.9-92.3%) were higher than those with human genogroup IV (GIV) NoVs (59.1-65.9%). The homology of the feline NoV isolate with previously reported feline NoV isolates was particularly high (91.7-92.3%). Regarding SaV, the two canine isolates were classified into the same clade as known canine SaVs and their homologies (72.5-86.5%) were higher than those with other mammal SaVs (20.7-58.0%). The eight feline VeV isolates were assumed to be feline calicivirus. The present study is the first report of the presence of NoV- and SaV-infected dogs and cats in Japan. The findings suggest there are species-specific circulations of NoV and SaV among dogs and cats, in Japan.

Histologic Lesions Induced by Murine Norovirus Infection in Laboratory Mice

Murine noroviruses (MNVs) are highly prevalent in laboratory mice, can cause persistent infections, and have been shown to infect macrophages, dendritic cells, and B cells. To address the potential impact of MNV infection on research outcomes, numerous studies have been conducted with various mouse models of human disease and have generated mixed results, ranging from no impact to significant disease. Many of these studies included histologic evaluations after MNV infection, and these results have similarly been variable in terms of whether MNV induces lesions, despite the fact that localization of MNV by viral culture and molecular techniques have demonstrated systemic distribution regardless of mouse immune status. The aim of this review is to summarize the histologic findings that have been reported with MNV infection in several mouse models. The studies demonstrate that experimental infection of MNV in wild-type mice results in minimal to no histologic changes. In contrast, immunodeficient mice consistently have detectable MNV-induced lesions that are typically inflammatory and, in the most severe cases, accompanied by necrosis. In these, the liver is commonly affected, with more variable lesions reported in the lung, gastrointestinal tract, mesenteric lymph nodes, brain, and spleen. In specific disease models including atherosclerosis, MNV infection had a variable impact that was dependent on the mouse model, viral strain, timing of infection, or other experimental variables. It is important to recognize the reported MNV lesions to help discern the possible influence of MNV infection on data generated in mouse models.

A novel feline norovirus in diarrheic cats

By screening a collection of fecal samples from young cats housed in three different shelters in South Italy, noroviruses (NoVs) were found in 3/48 (6.2%) specimens of animals with enteritis signs while they were not detected in samples collected from healthy cats (0/57). Upon sequence analysis of the short RNA-dependent RNA polymerase (RdRp) region, the three strains displayed the highest nucleotide (nt) and amino acid (aa) identities to the prototype GIV.2 strain lion/Pistoia/387/06/ITA (91.0–93.0% nt and 97.0–98.0% aa). The sequence of ~ 3.4-kb portion at the 3′ end of the genome of a NoV strain, TE/77-13/ITA, was determined. In the full-length ORF2, encoding the VP1 capsid protein, the virus was genetically closest to the canine GVI.2 NoV strains C33/Viseu/2007/PRT and FD53/2007/ITA (81.0–84.0% nt and 93.0–94.0% aa identities), suggesting a recombination nature, with the cross-over site being mapped to the ORF1-ORF2 junction. Based on the full-length VP1 amino acid sequence, we classified the novel feline NoV, together with the canine strains Viseu and FD53, as a genotype 2, within the genogroup GVI. These findings indicate that, as observed for GIV NoV, GVI strains may infect both the canine and feline host. Unrestricted circulation of NoV strains in small carnivores may provide the basis for quick genetic diversification of these viruses by recombination. Interspecies circulation of NoVs in pets must also be considered when facing outbreaks of enteric diseases in these animals.

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GIV and GVI NoVs have been recently found in domestic carnivores.

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In this study, NoV strains resembling animal GIV.2 NoVs in their polymerase region were detected in diarrheic cats.

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One Italian strain, TE/77-13/ITA, in the full-length VP1 sequence shared the highest identity to the canine GVI.2 NoVs.

An outbreak caused by GII.17 norovirus with a wide spectrum of HBGA-associated susceptibility

During the past norovirus (NoV) epidemic season, a new GII.17 variant emerged as a predominant NoV strain, surpassed the GII.4 NoVs, causing outbreaks of acute gastroenteritis (AGE) in China. Here we report a study of an AGE outbreak in an elementary school in December 2014 caused by the new GII.17 NoV to explore the potential mechanism behind the sudden epidemics of the GII.17 NoV. A total of 276 individuals were sick with typical NoV infection symptoms of vomiting (93.4%), abdominal pain (90.4%), nausea (60.0%), and diarrhea (10.4%) at an attack rate of 5.7–16.9%. Genotyping of the symptomatic patients showed that individuals with a secretor positive status, including those with A, B, and O secretors and Lewis positive blood types, were sensitive to the virus, while the non-secretors and the Lewis negative individual were not. Accordingly, the recombinant capsid P protein of the GII.17 isolate showed a wide binding spectrum to saliva samples of all A, B, and O secretors. Thus, the broad binding spectrum of the new GII.17 variant could explain its widely spread nature in China and surrounding areas in the past two years.

Molecular epidemiology of oyster-related human noroviruses and their global genetic diversity and temporal-geographical distribution from 1983 to 2014

Noroviruses (NoVs) are a leading cause of epidemic and sporadic cases of acute gastroenteritis worldwide. Oysters are well recognized as the main vectors of environmentally transmitted NoVs, and disease outbreaks linked to oyster consumption have been commonly observed. Here, to quantify the genetic diversity, temporal distribution, and circulation of oyster-related NoVs on a global scale, 1,077 oyster-related NoV sequences deposited from 1983 to 2014 were downloaded from both NCBI GenBank and the NoroNet outbreak database and were then screened for quality control. A total of 665 sequences with reliable information were obtained and were subsequently subjected to genotyping and phylogenetic analyses. The results indicated that the majority of oyster-related NoV sequences were obtained from coastal countries and regions and that the numbers of sequences in these regions were unevenly distributed. Moreover, >80% of human NoV genotypes were detected in oyster samples or oyster-related outbreaks. A higher proportion of genogroup I (GI) (34%) was observed for oyster-related sequences than for non-oyster-related outbreaks, where GII strains dominated with an overwhelming majority of >90%, indicating that the prevalences of GI and GII are different in humans and oysters. In addition, a related convergence of the circulation trend was found between oyster-related NoV sequences and human pandemic outbreaks. This suggests that oysters not only act as a vector of NoV through environmental transmission but also serve as an important reservoir of human NoVs. These results highlight the importance of oysters in the persistence and transmission of human NoVs in the environment and have important implications for the surveillance of human NoVs in oyster samples.

Human norovirus as a foodborne pathogen: challenges and developments

Human noroviruses (NoVs) are the leading cause of foodborne illness in the United States, and they exact a considerable human and economic burden worldwide. In fact, the many challenging aspects of human NoV have caused some to call it the nearly perfect foodborne pathogen. In this review, a brief overview of NoVs and their genetic structure is provided. Additionally, the challenges and recent developments related to human NoVs regarding viral evolution, transmission, epidemiology, outbreak identification, cultivation, animal and human models, and detection are presented.

Bovine noroviruses: A missing component of calf diarrhoea diagnosis

Noroviruses are RNA viruses that belong to the Genus Norovirus, Family Caliciviridae, and infect human beings and several animal species, including cattle. Bovine norovirus infections have been detected in cattle of a range of different ages throughout the world. Currently there is no suitable cell culture system for these viruses and information on their pathogenesis is limited. Molecular and serological tests have been developed, but are complicated by the high genetic and antigenic diversity of bovine noroviruses. Bovine noroviruses can be detected frequently in faecal samples of diarrhoeic calves, either alone or in association with other common enteric pathogens, suggesting a role for these viruses in the aetiology of calf enteritis.

Detection and molecular characterization of caliciviruses (vesivirus and norovirus) in an outbreak of acute diarrhea in kittens from Brazil

Feline caliciviruses (FCVs) have occasionally been described in cats in association with enteric disease, but an etiological role for these viruses in acute gastroenteritis is still unclear. In this study, molecular characterization of FCV and feline norovirus (FNoV) was undertaken using real-time PCR (RT-PCR) and sequence analysis of the ORF1 region in fecal specimens from 29 diarrheic cats. The specimens were also screened for parvovirus, coronavirus, astrovirus and group A rotavirus. A quantitative one step RT-PCR was also performed to detect and quantitate NoV genogroup IV and the role of these animal caliciviruses in feline gastroenteritis was investigated. This is the first description of enteric FCV and FNoV in South America.

Seroprevalence of norovirus genogroup IV antibodies among humans, Italy, 2010-2011

Antibodies specific to genogroup IV identified in human specimens suggest zoonotic exposure.

Noroviruses (NoVs) of genogroup IV (GIV) (Alphatron-like) cause infections in humans and in carnivorous animals such as dogs and cats. We screened an age-stratified collection of serum samples from 535 humans in Italy, using virus-like particles of genotypes GIV.1, circulating in humans, and GIV.2, identified in animals, in ELISA, in order to investigate the prevalence of GIV NoV-specific IgG antibodies. Antibodies specific for both genotypes were detected, ranging from a prevalence of 6.6% to 44.8% for GIV.1 and from 6.8% to 15.1% for GIV.2 among different age groups. These data are consistent with a higher prevalence of GIV.1 strains in the human population. Analysis of antibodies against GIV.2 suggests zoonotic transmission of animal NoVs, likely attributable to interaction between humans and domestic pets. This finding, and recent documentation of human transmission of NoVs to dogs, indicate the possibility of an evolutionary relationship between human and animal NoVs.

Antigenic Relatedness of Norovirus GII.4 Variants Determined by Human Challenge Sera

The GII.4 noroviruses (NoVs) are a single genotype that is responsible for over 50% of NoV gastroenteritis epidemics worldwide. However, GII.4 NoVs have been found to undergo antigenic drifts, likely selected by host herd immunity, which raises an issue for vaccine strategies against NoVs. We previously characterized GII.4 NoV antigenic variations and found significant levels of antigenic relatedness among different GII.4 variants. Further characterization of the genetic and antigenic relatedness of recent GII.4 variants (2008b and 2010 cluster) was performed in this study. The amino acid sequences of the receptor binding interfaces were highly conserved among all GII.4 variants from the past two decades. Using serum samples from patients enrolled in a GII.4 virus challenge study, significant cross-reactivity between major GII.4 variants from 1998 to 2012 was observed using enzyme-linked immunosorbent assays and HBGA receptor blocking assays. The overall abilities of GII.4 NoVs to bind to the A/B/H HBGAs were maintained while their binding affinities to individual ABH antigens varied. These results highlight the importance of human HBGAs in NoV evolution and how conserved antigenic types impact vaccine development against GII.4 variants.

Evidence for human norovirus infection of dogs in the United kingdom

Human noroviruses (HuNoVs) are a major cause of viral gastroenteritis, with an estimated 3 million cases per year in the United Kingdom. HuNoVs have recently been isolated from pet dogs in Europe (M. Summa, C.-H. von Bonsdorff, and L. Maunula, J Clin Virol 53:244–247, 2012, http://dx.doi.org/10.1016/j.jcv.2011.12.014), raising concerns about potential zoonotic infections. With 31% of United Kingdom households owning a dog, this could prove to be an important transmission route. To examine this risk, canine tissues were studied for their ability to bind to HuNoV in vitro. In addition, canine stool samples were analyzed for the presence of viral nucleic acid, and canine serum samples were tested for the presence of anti-HuNoV antibodies. The results showed that seven different genotypes of HuNoV virus-like particles (VLPs) can bind to canine gastrointestinal tissue, suggesting that infection is at least theoretically possible. Although HuNoV RNA was not identified in stool samples from 248 dogs, serological evidence of previous exposure to HuNoV was obtained in 43/325 canine serum samples. Remarkably, canine seroprevalence for different HuNoV genotypes mirrored the seroprevalence in the human population. Though entry and replication within cells have not been demonstrated, the canine serological data indicate that dogs produce an immune response to HuNoV, implying productive infection. In conclusion, this study reveals zoonotic implications for HuNoV, and to elucidate the significance of this finding, further epidemiological and molecular investigations will be essential.

The molecular pathology of noroviruses

Norovirus infection in humans typically results in acute gastroenteritis but may also occur in many animal species. Noroviruses are recognized as one of the most common causes of acute gastroenteritis in the world, being responsible for almost 20% of all cases. Despite their prevalence and impact, our knowledge of the norovirus life cycle and the pathological processes associated with norovirus-induced disease is limited. Whilst infection of the intestine is the norm, extraintestinal spread and associated pathologies have also been described. In addition, long-term chronic infections are now recognized as a significant cause of morbidity and mortality in the immunocompromised. This review aims to summarize the current state of knowledge with respect to norovirus pathology and the underlying mechanisms that have been characterized to date.

Norovirus GII.17 Predominates in Selected Surface Water Sources in Kenya

In this study, the prevalence and genotypes of noroviruses (NoVs) in selected water sources from rural, urban and refugee settings in Kenya were investigated. Ten litres each of river, household and borehole water was collected in rural (Mboone River), urban (Nairobi and Mutoine River) and refugee (Dadaab refugee camp) settings. NoVs were recovered from the water samples by a glass wool adsorption-elution technique and/or PEG/NaCl precipitation. Nucleic acid was extracted using the automated MagNA Pure platform. NoVs were detected with singleplex real-time reverse transcription-polymerase chain reaction assays and characterised by nucleotide sequence analysis. NoVs were detected in 63% (25/40) of the selected water samples comprising GII (42.5%), GI (2.5%) and mixed GI/GII (17.5%) positive samples. The prevalence of NoVs in the Mutoine River (urban area) was higher than in the Mboone River (rural area) (P = 0.0013). Noroviruses GI.1, GI.3, GI.9, GII.4, GII.6, GII.12, GII.16 and GII.17 were identified, with GII.17 accounting for 76% (16/21) of the typed strains. The NoV GII.17 predominance differs to other studies in Africa and further surveillance of NoVs in clinical and environmental settings is required to clarify/elucidate this observation. As information regarding NoVs in Kenyan water sources is limited this report provides valuable new data on NoV genotypes circulating in environmental water sources and the surrounding communities in Kenya.