Detection and molecular characteristics of neboviruses in dairy cows in China

Comprehensive Genomics Investigation of Neboviruses Reveals Distinct Codon Usage Patterns and Host Specificity

Neboviruses (NeVs) from the Caliciviridae family have been linked to enteric diseases in bovines and have been detected worldwide. As viruses rely entirely on the cellular machinery of the host for replication, their ability to thrive in a specific host is greatly impacted by the specific codon usage preferences. Here, we systematically analyzed the codon usage bias in NeVs to explore the genetic and evolutionary patterns. Relative Synonymous Codon Usage and Effective Number of Codon analyses indicated a marginally lower codon usage bias in NeVs, predominantly influenced by the nucleotide compositional constraints. Nonetheless, NeVs showed a higher codon usage bias for codons containing G/C at the third codon position. The neutrality plot analysis revealed natural selection as the primary factor that shaped the codon usage bias in both the VP1 (82%) and VP2 (57%) genes of NeVs. Furthermore, the NeVs showed a highly comparable codon usage pattern to bovines, as reflected through Codon Adaptation Index and Relative Codon Deoptimization Index analyses. Notably, yak NeVs showed considerably different nucleotide compositional constraints and mutational pressure compared to bovine NeVs, which appear to be predominantly host-driven. This study sheds light on the genetic mechanism driving NeVs' adaptability, evolution, and fitness to their host species.

Isolation and Characteristics of a Novel Aichivirus D from Yak

Aichivirus D (AiV-D) is a newly emerging Kobuvirus detected in bovine and sheep, and information is limited regarding its biological significance and prevalence. This study aimed to explore both the prevalence and characteristics of AiV-D in yaks. From May to August 2021, 117 fecal samples were collected from yaks with diarrhea in three provinces of China's Qinghai-Tibet Plateau, 15 of which were selected and pooled for metagenomic analysis. A high abundance of AiV-D sequences was obtained. Of the 117 diarrhea samples, 29 (24.8%) tested AiV-D-positive, including 33.3% (14/42) from Sichuan, 21.1% (8/38) from Qinghai, and 18.9% (7/37) from Tibet, respectively, suggesting a wide geographical distribution of the AiV-D in yaks in the Qinghai-Tibet Plateau. Furthermore, three AiV-D strains were successfully isolated using Vero cells. Significantly, the AiV-D strain could cause diarrhea, intestinal bleeding, and inflammation in yak calves via oral inoculation. The virus was distributed in the ileum, jejunum, duodenum, colon, cecum, and rectum. Based on phylogenetic analysis of the genome and capsid protein P1 (VP0, VP3, and VP1 genes), the yak AiV-D strains likely represent a novel genotype of AiV-D. On the whole, this study identified a novel genotype of AiV-D from yaks, which was successfully isolated, and confirmed that this virus is a diarrhea pathogen in yaks and has a wide geographical distribution in the Qinghai-Tibet Plateau. Our results expand the host range of AiV-D and the pathogen spectrum of yaks and have significant implications for diagnosing and controlling diarrhea in yaks. IMPORTANCE In this study, we identified and successfully isolated a novel genotype of AiV-D from yaks. Animal infection confirmed that this virus can cause diarrhea, intestinal bleeding, and inflammation in yak calves via oral inoculation. The virus was distributed in the ileum, jejunum, cecum, duodenum, colon, and rectum. All of these results have significant implications for diagnosing and controlling diarrhea in yaks. These novel AiV-D strains have a wide geographical distribution in yaks from the Qinghai-Tibet Plateau in China. In addition to expanding the host range of AiV-D and the pathogen spectrum of yaks, these findings can increase knowledge of the prevalence and diversity of AiV-D.

Detection of the dominant pathogens in diarrheal calves of Ningxia, China in 2021-2022

Introduction

Calf diarrhea is a complex disease that has long been an unsolved problem in the cattle industry. Ningxia is at the forefront of China in the scale of cattle breeding, and calf diarrhea gravely restricts the development of Ningxia's cattle industry.

Methods

From July 2021 to May 2022, we collected diarrhea stool samples from calves aged 1-103 days from 23 farms in five cities in Ningxia, and performed PCR using specific primers for 15 major reported pathogens of calf diarrhea, including bacteria, viruses, and parasites. The effect of different seasons on the occurrence of diarrhea in calves was explored, the respective epidemic pathogens in different seasons were screened, and more detailed epidemiological investigations were carried out in Yinchuan and Wuzhong. In addition, we analyzed the relationship between different ages, river distributions and pathogen prevalence.

Results

Eventually, 10 pathogens were detected, of which 9 pathogens were pathogenic and 1 pathogen was non-pathogenic. The pathogens with the highest detection rate were Cryptosporidium (50.46%), Bovine rotavirus (BRV) (23.18%), Escherichia coli (E. coli) K99 (20.00%), and Bovine coronavirus (BCoV) (11.82%). The remaining pathogens such as Coccidia (6.90%), Bovine Astrovirus (BoAstV) (5.46%), Bovine Torovirus (BToV) (4.09%), and Bovine Kobuvirus (BKoV) (3.18%) primarily existed in the form of mixed infection.

Discussion

The analysis showed that different cities in Ningxia have different pathogens responsible for diarrhea, with Cryptosporidium and BRV being the most important pathogens responsible for diarrhea in calves in all cities. Control measures against those pathogens should be enforced to effectively prevent diarrhea in calves in China.

Isolation and Identification of Two Clinical Strains of the Novel Genotype Enterovirus E5 in China

Most enterovirus (EV) infections are subclinical but, occasionally, can cause severe and potentially fatal diseases in humans and animals. Currently, EVs are divided into 12 types (A to L) based on phylogenetic analysis and on their natural hosts. Bovine enterovirus (BEV) is an essential member of the enterovirus belonging to the types E and F that attacks cattle as its natural host and causes clinical disorders in the digestive, respiratory, and reproductive tracts. In 2020, several dairy farms in China experienced cow mortality with acute clinical signs, including fever, and diarrhea. In these cases, GX20-1 and JS20-1 virus strains were isolated and sequenced. Cellular adaptation of these two strains showed efficient replications on Madin-Darby bovine kidney (MDBK) cells and produced a significant cytopathogenic effect (CPE). However, on baby hamster kidney (BHK-21) and Vero cells, viral replication was inefficient and did not produce CPE. As noted in comparative genomics analysis, these two strains showed distant evolutionary relationships with the well-known E1 to E4 and F1 to F4 subtypes of BEV and high sequence identities with the candidate type Enterovirus E5, a novel genotype recently identified based on the genomic data of three strains, including the GX20-1 and JS20-1 strains. This study provides the first evidence of a novel genotype bovine enterovirus infection in Chinese cattle herds, a potential threat to the cattle industry in China.

IMPORTANCE Bovine enterovirus (BEV) is a cattle-infecting pathogen. This study is the first report of natural infection of a novel genotype of enterovirus in herds of cattle in China. The homology of the novel enterovirus is far different from the structural protein of other enteroviruses and has different cellular adaptations. This study provides a reference for the biological characteristics and prevalence of the novel enterovirus in Chinese cattle populations.

Prevalence of Bovine Norovirus and Nebovirus and Risk Factors of Infection in Swedish Dairy Herds

Enteritis is the major cause of mortality in neonatal calves. Diagnostic work to detect the pathogens involved and identification of risk factors for such infections are imperative to improve calf health. Bovine norovirus (BNoV) and nebovirus prevalence was investigated using RT-PCR in 50 dairy herds in five geographic regions of Sweden. BNoV and nebovirus were found to be common infections in young dairy calves. BNoV was detected in 20% of 250 calves in 48% of the herds. Nebovirus was detected in 5% of the calves in 16% of the herds. Both infections were present in three herds (6%). BNoV-infected calves were younger (median age 7 days) than nebovirus-infected calves (median age 21 days). These infections were not detected in adult cows and young stock over 6 months of age tested in selected herds. Risk factors identified for BNoV infection were a high number of preweaned calves present at the time of sampling, colostrum uptake by suckling the dam only, calf kept in a single pen, and geographic location of herd, while no risk factors for nebovirus infection were identified in the multivariable analysis. Univariable analysis suggested risk factors for nebovirus infection to be geographic location and early separation from the dam.

Literature Review: Coinfection in Young Ruminant Livestock-Cryptosporidium spp. and Its Companions

The protozoan Cryptosporidium parvum is one of the major causative pathogens of diarrhoea in young ruminants; therefore, it causes economic losses and impairs animal welfare. Besides C. parvum, there are many other non-infectious and infectious factors, such as rotavirus, Escherichia coli, and Giardia duodenalis, which may lead to diarrhoeic disease in young livestock. Often, more than one infectious agent is detected in affected animals. Little is known about the interactions bet-ween simultaneously occurring pathogens and their potential effects on the course of disease. In this review, a brief overview about pathogens associated with diarrhoea in young ruminants is presented. Furthermore, information about coinfections involving Cryptosporidium is provided.

Comparison of gut viral communities in diarrhoea and healthy dairy calves

Calf diarrhoea has been a major cause of economic losses in the global dairy industry. Many factors, including multiple pathogen infections, can directly or indirectly cause calf diarrhoea. This study compared the faecal virome between 15 healthy calves and 15 calves with diarrhoea. Significantly lower diversity of viruses was found in samples from animals with diarrhoea than those in the healthy ones, and this feature may also be related to the age of the calves. Viruses belonging to the families Astroviridae and Caliciviridae that may cause diarrhoea in dairy calves have been characterized, which revealed that reads of caliciviruses and astroviruses in diarrhoea calves were much higher than those in healthy calves. Five complete genomic sequences closely related to Smacoviridae have been identified, which may participate in the regulation of the gut virus community ecology of healthy hosts together with bacteriophages. This research provides a theoretical basis for further understanding of known or potential enteric pathogens related to calf diarrhoea.

Prevalence of bovine astroviruses and their genotypes in sampled Chinese calves with and without diarrhoea

Bovine astrovirus (BoAstV) belongs to genus Mamastravirus (MAstV). It can be detected in the faeces of both diarrhoeal and healthy calves. However, its prevalence, genetic diversity, and association with cattle diarrhoea are poorly understood. In this study, faecal samples of 87 diarrhoeal and 77 asymptomatic calves from 20 farms in 12 provinces were collected, and BoAstV was detected with reverse transcription-polymerase chain reaction (RT-PCR). The overall prevalence rate of this virus in diarrhoeal and asymptomatic calves was 55.17 % (95 % CI: 44.13, 65.85 %) and 36.36 % (95 % CI: 25.70, 48.12 %), respectively, indicating a correlation between BoAstV infection and calf diarrhoea (OR=2.15, P=0.024). BoAstV existed mainly in the form of co-infection (85.53 %) with one to five of nine viruses, and there was a strong positive correlation between BoAstV co-infection and calf diarrhoea (OR=2.83, P=0.004). Binary logistic regression analysis confirmed this correlation between BoAstV co-infection and calf diarrhoea (OR=2.41, P=0.038). The co-infection of BoAstV and bovine rotavirus (BRV) with or without other viruses accounted for 70.77 % of all the co-infection cases. The diarrhoea risk for the calves co-infected with BoAstV and BRV was 8.14-fold higher than that for the calves co-infected with BoAstV and other viruses (OR=8.14, P=0.001). Further, the co-infection of BoAstV/BRV/bovine kobuvirus (BKoV) might increase the risk of calf diarrhoea by 14.82-fold, compared with that of BoAstV and other viruses (OR=14.82, P <0.001). Then, nearly complete genomic sequences of nine BoAstV strains were assembled by using next-generation sequencing (NGS) method. Sequence alignment against known astrovirus (AstV) strains at the levels of both amino acids and nucleotides showed a high genetic diversity. Four genotypes were identified, including two known genotypes MAstV-28 (n=3) and MAstV-33 (n=2) and two novel genotypes designated tentatively as MAstV-34 (n=1) and MAstV-35 (n=3). In addition, seven out of nine BoAstV strains showed possible inter-genotype recombination and cross-species recombination. Therefore, our results increase the knowledge about the prevalence and the genetic evolution of BoAstV and provide evidence for the association between BoAstV infection and calf diarrhoea.

Detection and molecular characteristics of bovine rotavirus A in dairy calves in China

Background

Bovine group A rotavirus (BoRVA) is a major cause of severe gastroenteritis in newborn dairy calves. Only one study has investigated the G and P genotypes among dairy calves in a few regions of China, which were G6 and P[5]. Therefore, data on the prevalence and molecular characteristics of BoRVA in dairy calves in China remains limited.

Objectives

The purpose of this study was to investigate the prevalence and molecular characteristics of BoRVA in dairy calves in China.

Methods

269 dairy calves diarrheic samples from 23 farms in six provinces in China were collected to detect BoRVA using reverse transcription polymerase chain reaction.

Results

71% of samples were determined to be BoRVA-positive. Two G genotypes (G6, G10) and two P genotypes (P[1], P[5]) were identified, and G6P[1] BoRVA was the predominant strain. Moreover, the VP7 and VP4 gene sequences of these dairy calf BoRVA strains revealed abundant genetic diversity. Interestingly, eight out of 17 complete G6 VP7 sequences were clustered into G6 lineage VI and analysis showed the strains were closely related to Chinese yak BoRVA strains.

Conclusions

The results of this study show that BoRVA circulates widely among dairy calves in China, and the dominant genotype in circulation is G6P[1], first report on molecular characteristics of complete P[5] VP4 genes in chinese dairy calves. These results will help us to further understand the prevalence and genetic evolution of BoRVA among dairy calves in China and, thus, prevent the disease more effectively.

Viral Enteritis in Cattle: To Well Known Viruses and Beyond

Livestock products supply about 13 percent of energy and 28 percent of protein in diets consumed worldwide. Diarrhea is a leading cause of sickness and death of beef and dairy calves in their first month of life and also affecting adult cattle, resulting in large economic losses and a negative impact on animal welfare. Despite the usual multifactorial origin, viruses are generally involved, being among the most important causes of diarrhea. There are several viruses that have been confirmed as etiological agents (i.e., rotavirus and coronavirus), and some viruses that are not yet confirmed as etiological agents. This review summarizes the viruses that have been detected in the enteric tract of cattle and tries to deepen and gather knowledge about them.

High prevalence and genomic characteristics of G6P[1] Bovine Rotavirus A in yak in China

Yak is an iconic species of the Qinghai-Tibet Plateau, which is the world's highest plateau. Here, a total of 541 yak diarrhoeic samples were collected from 69 farms in four provinces in the Qinghai-Tibet Plateau from April 2015 to June 2018, and 73.6 % of samples were detected as Bovine Rotavirus A (BRVA) positive by RT-PCR assay. Two G genotypes (G6, G10) and two P genotypes (P[1], P[11]) were determined, in which G6P[1] BRVA was the predominant strain. Moreover, VP7 and VP4 of these G6P[1] strains showed unique amino acid mutations, such that they clustered into an independent branch in the phylogenetic tree. A strain of BRVA designated as RVA/Yak-tc/CHN/QH-1/2015/G6P[1] was isolated successfully using MA104 cells, and the virus titre was determined as 10^5.84 TCID₅₀ ml^-1. The genome of strain QH-1 had a G6-P[1]-I2-R2-C2-M2-A3-N3-T6-E2-H3 genotype constellation. QH-1 was identified as a reassortment strain of BRVA, human RVA and ovine RVA based on the nucleotide identity and phylogenetic tree of 11 gene segments, indicating its public health significance. To the best of our knowledge, this is the first report on the molecular prevalence and genome characteristics of BRVA in yak, contributing to further understanding of the epidemic and genetic evolution of BRVA.

Genomic characterization of a nebovirus strain with a novel RdRp genotype in yaks

Neboviruses (NeVs) are important causative agents of calf diarrhea that belong to the family Caliciviridae. In this study, we investigated the genomic characteristics of a NeV strain from yaks that has a novel RdRp genotype. The complete genome of this strain (YAK/NRG-A9/19/CH) is 7454 nt in length and shares 68.3%-79.7% nt sequence identity with those of other NeVs. The RNA-dependent RNA polymerase (RdRp) gene of this strain shares 66.5%-78.5% nt sequence identity (74.0%-89.3% aa sequence identity) with the eight available complete NeV RdRp sequences, and a phylogenetic analysis based on these sequences showed that the new strain formed an independent branch, indicating that the RdRp of strain YAK/NRG-A9/19/CH may represent a novel RdRp genotype of NeV. These results contribute to a further understanding of the molecular characteristics and genetic evolution of NeVs.

First detection and genomic characteristics of bovine torovirus in dairy calves in China

Bovine torovirus (BToV) is a diarrhea-causing pathogen. In this study, 92 diarrheic fecal samples from five farms in four provinces in China were collected and tested for BToV using a RT-PCR assay, and 21.73% samples were found to be BToV positive. Moreover, two complete BToV genome sequences (MN073058 and MN073059) were obtained from the clinical samples, which were 28,297 and 28,301 nucleotides in length, respectively. Sequence analysis showed that the two isolates shared 10 identical amino acid mutations in the S protein compared to the complete S sequences of BToV available in the GenBank database. In addition, seven consecutive amino acid mutations were found from aa 1,486 to 1,492 in the S protein of isolate MN073058. Moreover, the two isolates shared one identical amino acid mutation in the receptor binding sites of the HE protein. To the best of our knowledge, this is the first report on the epidemic and genomic characterization of BToV in China, which is helpful for further understanding the genetic evolution of BToV.

Prevalence and complete genome of bovine norovirus with novel VP1 genotype in calves in China

Bovine norovirus (BNoV) is a diarrhea-causing pathogen of calves. In this study, 211 diarrheic fecal samples were collected from 25 farms across six provinces in China, between November 2017 and September 2018. 20.4% of the samples were detected as BNoV-positive by RT-PCR. Phylogenetic analyses based on RdRp, VP1, and VP2 fragments revealed these BNoV strains had unique evolutionary characteristics. The complete genome of strain Bo/BET-17/18/CH was successfully sequenced. It was 7321 nucleotides (nt) in length, shared 79.4-80.9% nt identity with all five BNoV genomes, clustered on a separate branch of the phylogenetic tree, suggesting that strain Bo/BET-17/18/CH could represent a novel BNoV strain. Two interesting characteristics were found in the genome: (i) the VP1 sequence differed greatly from known BNoV VP1 sequences; (ii) a recombination event is predicted within the ORF1-ORF2 overlap. Moreover 16.3% (7/43) of the BNoV were identified as the novel VP1 genotype, which were distributed on four farms across two provinces, indicating that the novel VP1 genotype strain has spread. To our knowledge, this is first description of the molecular and genomic characteristics of BNoV in China. These findings extend our understanding of the genetic evolution and epidemics of BNoV.

First detection of neboviruses in yak (Bos grunniens) and identification of a novel neboviruses based on complete genome

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This is the first detection of neboviruses in yak (Bos grunniens).

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Neboviruses has been widely circulated among yak in Qinghai-Tibet Plateau, China.

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A novel neboviruses was identified, and it has spread in local region.

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New insights about the prevalence and evolution of neboviruses.

Neboviruses (NeVs) is an important causative agent of calf diarrhea. Here, 354 diarrhoeic samples were collected from yak on 55 farms in the Qinghai-Tibet Plateau, China. 22.0% of the diarrhoeic samples were detected as NeVs-positive by RT–PCR assay. Phylogenetic analysis of 78 NeVs RdRp fragments showed that 69 strains were closely related to NB-like strains, and the remaining 9 strains were clustered into an independent branch, which may represent a novel RdRp genotype. Two complete NeVs genomes (YAK/NRG-17/17/CH and YAK/HY1-2/18/CH) were successfully sequenced with 7459 nt and 7460 nt in length, respectively. The genomes of the two strains only shared 68.1%–69.3% nt identity with all six known NeVs genomes, and phylogenetic trees based on its genome, VP1, RdRp, VP2, P34, NTPase, P30, VPg and 3CLpro proteins suggested that the two strains may represent a novel NeVs strain with novel VP1 genotype and novel RdRp genotype. Notably, 11.5% NeVs strains were screened as the novel NeVs strains based VP1 and RdRp sequences. These novel NeVs strains were detected from 6 farms in two counties, indicating that the novel NeVs has spread in local region. To best of our knowledge, this is the first detection of NeVs in yak. Moreover, a novel NeVs strain was identified based on complete genome. These results contribute to further understand the prevalence and genetic evolution of NeVs.

Molecular detection and genomic characteristics of bovine kobuvirus from dairy calves in China

In this study, 96 diarrheic and 77 non-diarrheic fecal samples from dairy calves were collected from 14 dairy farms in 4 provinces to investigate the molecular prevalence and genomic characteristics of Bovine Kobuvirus (BKoV) in China. The results showed that the BKoV positive rate for the diarrheic feces (35.42%) was significantly higher than that for the non-diarrheic feces (11.69%, p < 0.001). Interestingly, three potential novel VP1 lineages were identified from 15 complete VP1 sequences, and a unique triple nucleotide insertion which can result in an aa insertion, was first observed in the 11/12 VP0 fragments with 660 bp long in this study, compared with known BKoV VP0 sequences. Moreover, the first Chinese BKoV genome was successfully obtained from a diarrheic fecal sample, named CHZ/CHINA. The open reading frame (ORF) of the genome from strain CHZ/China shares 87.4%–88.3% nucleotide (nt) and 93.7%–96.4% amino acid (aa) identity, compared with the three known genomes of BKoV. Interestingly, phylogenetic tree based on aa sequences of these genomes showed that CHZ/CHINA was clustered into an independent branch, suggesting the strain may represent a novel BKoV strain. The findings contribute to better understanding the molecular characteristics and evolution of BKoV.

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Three potential novel VP1 lineages in BKoV.

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A unique VP0 sequence type in BKoV.

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The first BKoV genome from China which may represent a novel BKoV strain.

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Contributing to better understanding the molecular characteristics of BKoV.

First detection of bovine coronavirus in Yak (Bos grunniens) and a bovine coronavirus genome with a recombinant HE gene

The yak (Bosgrunniens) is a unique domestic bovine species that plays an indispensable role for herdsmen in the Qinghai–Tibet Plateau. Here, 336 diarrhoeic samples were collected from yaks on 29 farms in the Qinghai–Tibet Plateau from 2015 to 2017. Approximately 69.05 % (232/336) of the diarrhoeic samples were assessed as bovine coronavirus (BCoV)-positive by RT-PCR assay, and most of the detected strains showed a unique evolution based on 40 spike (S), nucleocapsid (N) and haemagglutinin-esterase (HE) gene fragments. Notably, the 12 complete S genes detected shared 1 identical amino acid mutation (E121V) in the S1 subunit compared with the other 150 complete S genes in the GenBank database. Furthermore, a BCoV strain (designated YAK/HY24/CH/2017) was isolated from one diarrhoeic sample (virus titre : 10^8.17TCID₅₀ ml⁻¹), and a phylogenetic analysis based on complete genome sequences revealed that strain YAK/HY24/CH/2017 has the closest genetic relationship with the BCoV prototype strain Mebus. Interestingly, 2 significant characteristics were observed in the genome of strain YAK/HY24/CH/2017 :  (1) the strain had 26 unique amino acid variations in the S gene compared with the other 150 BCoV S genes in the GenBank database and (2) a recombination event was identified between the esterase and lectin domains of the HE gene. In conclusion, this study revealed the high prevalence of BCoV in yaks in the Qinghai–Tibet Plateau. To the best of our knowledge, this is the first description of the molecular prevalence of BCoV in yaks and of a BCoV genome with an HE gene recombination.

Caliciviridae Other Than Noroviruses

Besides noroviruses, the Caliciviridae family comprises four other accepted genera: Sapovirus, Lagovirus, Vesivirus, and Nebovirus. There are six new genera proposed: Recovirus, Valovirus, Bavovirus, Nacovirus, Minovirus, and Salovirus. All Caliciviridae have closely related genome structures, but are genetically and antigenically highly diverse and infect a wide range of mammalian host species including humans. Recombination in nature is not infrequent for most of the Caliciviridae, contributing to their diversity. Sapovirus infections cause diarrhoea in pigs, humans and other mammalian hosts. Lagovirus infections cause systemic haemorrhagic disease in rabbits and hares, and vesivirus infections lead to lung disease in cats, vesicular disease in swine, and exanthema and diseases of the reproductive system in large sea mammals. Neboviruses are an enteric pathogen of cattle, differing from bovine norovirus. At present, only a few selected caliciviruses can be propagated in cell culture (permanent cell lines or enteroids), and for most of the cultivatable caliciviruses helper virus-free, plasmid only-based reverse genetics systems have been established. The replication cycles of the caliciviruses are similar as far as they have been explored: viruses interact with a multitude of cell surface attachment factors (glycans) and co-receptors (proteins) for adsorption and penetration, use cellular membranes for the formation of replication complexes and have developed mechanisms to circumvent innate immune responses. Vaccines have been developed against lagoviruses and vesiviruses, and are under development against human noroviruses.