Enteric caliciviruses in domestic pigs in Hungary

The Complexity of Swine Caliciviruses. A Mini Review on Genomic Diversity, Infection Diagnostics, World Prevalence and Pathogenicity

Caliciviruses are single stranded RNA viruses, non-enveloped structurally, that are implicated in the non-bacterial gastroenteritis in various mammal species. Particularly in swine, viral gastroenteritis represents a major problem worldwide, responsible for significant economic losses for the pig industry. Among the wide range of viruses that are the proven or suspected etiological agents of gastroenteritis, the pathogenicity of the members of Caliciviridae family is among the less well understood. In this context, the present review presents and discusses the current knowledge of two genera belonging to this family, namely the Norovirus and the Sapovirus, in relation to swine. Aspects such as pathogenicity, clinical evidence, symptoms, epidemiology and worldwide prevalence, genomic diversity, identification tools as well as interchanging hosts are not only reviewed but also critically evaluated. Generally, although often asymptomatic in pigs, the prevalence of those microbes in pig farms exhibits a worldwide substantial increasing trend. It should be mentioned, however, that the factors influencing the symptomatology of these viruses are still far from well established. Interestingly, both these viruses are also characterized by high genetic diversity. These high levels of molecular diversity in Caliciviridae family are more likely a result of recombination rather than evolutionary or selective adaptation via mutational steps. Thus, molecular markers for their detection are mostly based on conserved regions such as the RdRp region. Finally, it should be emphasized that Norovirus and the Sapovirus may also infect other domestic, farm and wild animals, including humans, and therefore their surveillance and clarification role in diseases such as diarrhea is a matter of public health importance as well.

Swine Norovirus: Past, Present, and Future

Norovirus, an ssRNA + virus of the family Caliciviridae, is a leading disease burden in humans worldwide, causing an estimated 600 million cases of acute gastroenteritis every year. Since the discovery of norovirus in the faeces of swine in Japan in the 1990s, swine norovirus has been reported in several countries on several continents. The identification of the human-associated GII.4 genotype in swine has raised questions about this animal species as a reservoir of norovirus with zoonotic potential, even if species-specific P-types are usually detected in swine. This review summarises the available data regarding the geographic distribution of norovirus in swine, the years of detection, the genotype characterisation, and the prevalence in specific production groups. Furthermore, we discuss the major bottlenecks for the detection and characterisation of swine noroviruses.

Porcine sapoviruses: Pathogenesis, epidemiology, genetic diversity, and diagnosis

The first porcine Sapovirus (SaV) Cowden strain was discovered in 1980. To date, eight genogroups (GIII, V-IX) and three genogroups (GIII, GV, and GVI) of porcine SaVs have been detected from domestic pigs worldwide and wild boars in Japan, respectively based on the capsid sequences. Although GIII Cowden strain replicated in the villous epithelial cells and caused intestinal lesions in the proximal small intestines (mainly in duodenal and less in jejunum), leading to mild to severe diarrhea, in the orally inoculated neonatal gnotobiotic pigs, the significance of porcine SaVs in different ages of pigs with diarrhea in the field is still undetermined. This is due to two reasons: 1) similar prevalence of porcine SaVs was detected in diarrheic and non-diarrheic pigs; and 2) co-infection of porcine SaVs with other enteric pathogens is common in pigs. Diagnosis of porcine SaV infection is mainly based on the detection of viral nucleic acids using reverse transcription (RT)-PCR and sequencing. Much is unknown about these genetically diverse viruses to understand their role in pig health and to evaluate whether vaccines are needed to prevent SaV infection.

Identification of two divergent swine Noroviruses detected at the slaughterhouse in North East Italy

Norovirus (NoV) has emerged as one of the major causative agents of non-bacterial, food- and water-borne gastroenteritis in humans, with the main genogroup involved in human outbreaks (GII), which has been detected worldwide in different animal species including swine. A four-month investigation at the slaughterhouse aiming to examine the presence of NoV in the swine in North-Eastern Italy, enabled the detection of two divergent Noroviruses (NoVs) (GII.P11) in two swine farms. This represents the first study in the swine population of North-Eastern Italy, which has paved the way for future integrated virological and epidemiological investigations on swine NoVs.

One-step triplex reverse-transcription PCR detection of porcine epidemic diarrhea virus, porcine sapelovirus, and porcine sapovirus

Swine diarrhea can be caused by multiple agents, including porcine epidemic diarrhea virus (PEDV), porcine sapelovirus (PSV), and porcine sapovirus (SaV). We designed a one-step triplex reverse-transcription PCR (RT-PCR) detection method including 3 pairs of primers that focused on the S1 gene of PEDV, a conserved gene of PSV, and the VP1 gene of SaV. The optimal concentrations of upstream and downstream primers in the triplex RT-PCR were 0.24 μM for PEDV, 0.15 μM for PSV, and 0.2 μM for SaV, and the optimal annealing temperature was 55.5°C. Triplex RT-PCR assessment of 402 piglet diarrhea samples was compared with conventional individual RT-PCR. Concordance rates in both tests for individual viruses were 100%, 97.6%, and 94.4% for PEDV, PSV, and SaV, respectively. PEDV, PSV, and SaV were detected in 57.2%, 10.4%, and 9.0% of the samples, respectively. The high sensitivity and specificity of this triplex RT-PCR-based detection method for PEDV, PSV, and SaV could allow rapid detection and analysis of mixed infections by these 3 viruses.

Animals as Reservoir for Human Norovirus

Norovirus is the most common cause of non-bacterial gastroenteritis and is a burden worldwide. The increasing norovirus diversity is currently categorized into at least 10 genogroups which are further classified into more than 40 genotypes. In addition to humans, norovirus can infect a broad range of hosts including livestock, pets, and wild animals, e.g., marine mammals and bats. Little is known about norovirus infections in most non-human hosts, but the close genetic relatedness between some animal and human noroviruses coupled with lack of understanding where newly appearing human norovirus genotypes and variants are emerging from has led to the hypothesis that norovirus may not be host restricted and might be able to jump the species barrier. We have systematically reviewed the literature to describe the diversity, prevalence, and geographic distribution of noroviruses found in animals, and the pathology associated with infection. We further discuss the evidence that exists for or against interspecies transmission including surveillance data and data from in vitro and in vivo experiments.

Bovine Nebovirus Interacts with a Wide Spectrum of Histo-Blood Group Antigens

Some viruses within the Caliciviridae family initiate their replication cycle by attachment to cell surface carbohydrate moieties, histo-blood group antigens (HBGAs), and/or terminal sialic acids (SAs). Although bovine nebovirus (BNeV), one of the enteric caliciviruses, is an important causative agent of acute gastroenteritis in cattle, its attachment factors and possibly other cellular receptors remain unknown. Using a comprehensive series of protein-ligand biochemical assays, we sought to determine whether BNeV recognizes cell surface HBGAs and/or SAs as attachment factors. It was found that BNeV virus-like particles (VLPs) bound to A type/H type 2/Le^y HBGAs expressed in the bovine digestive tract and are related to HBGAs expressed in humans and other host species, suggesting a wide spectrum of HBGA recognition by BNeV. BNeV VLPs also bound to a large variety of different bovine and human saliva samples of all ABH and Lewis types, supporting previously obtained results and suggesting a zoonotic potential of BNeV transmission. Removal of α1,2-linked fucose and α1,3/4-linked fucose epitopes of target HBGAs by confirmation-specific enzymes reduced the binding of BNeV VLPs to synthetic HBGAs, bovine and human saliva, cultured cell lines, and bovine small intestine mucosa, further supporting a wide HBGA binding spectrum of BNeV through recognition of α1,2-linked fucose and α1,3/4-linked fucose epitopes of targeted HBGAs. However, removal of terminal α2,3- and α2,6-linked SAs by their specific enzyme had no inhibitory effects on binding of BNeV VLPs, indicating that BNeV does not use terminal SAs as attachment factors. Further details of the binding specificity of BNeV remain to be explored.

IMPORTANCE Enteric caliciviruses such as noroviruses, sapoviruses, and recoviruses are the most important etiological agents of severe acute gastroenteritis in humans and many other mammalian host species. They initiate infection by attachment to cell surface carbohydrate moieties, HBGAs, and/or terminal SAs. However, the attachment factor(s) for BNeV, a recently classified enteric calicivirus genus/type species, remains unexplored. Here, we demonstrate that BNeV VLPs have a wide spectrum of binding to synthetic HBGAs, bovine and human saliva samples, and bovine duodenal sections. We further discovered that α1,2-linked fucose and α1,3/4-linked fucose epitopes are essential for binding of BNeV VLPs. However, BNeV VLPs do not bind to terminal SAs on cell carbohydrates. Continued investigation regarding the proteinaceous receptor(s) will be necessary for better understanding of the tropism, pathogenesis, and host range of this important viral genus.

Genetic diversity and intergenogroup recombination events of sapoviruses detected from feces of pigs in Japan

Sapoviruses (SaV) are enteric viruses infecting humans and animals. SaVs are highly diverse and are divided into multiple genogroups based on structural protein (VP1) sequences. SaVs detected from pigs belong to eight genogroups (GIII, GV, GVI, GVII, GVIII, GIX, GX, and GXI), but little is known about the SaV genogroup distribution in the Japanese pig population. In the present study, 26 nearly complete genome (>6000 nucleotide: nt) and three partial sequences (2429nt, 4364nt, and 4419nt in length, including the entire VP1 coding region) of SaV were obtained from one diarrheic and 15 non-diarrheic porcine feces in Japan via a metagenomics approach. Phylogenetic analysis of the complete VP1 amino acid sequence (aa) revealed that 29 porcine SaVs were classified into seven genogroups; GIII (11 strains), GV (1 strain), GVI (3 strains), GVII (6 strains), GVIII (1 strain), GX (3 strains), and GXI (4 strains). This manuscript presents the first nearly complete genome sequences of GX and GXI, and demonstrates novel intergenogroup recombination events.

Detection and molecular characterization of zoonotic viruses in swine fecal samples in Italian pig herds

Gastrointestinal disease is frequent in pigs, and among the different etiological agents involved, viruses are considered the leading cause of infection in this animal species. Furthermore, about half of the newly identified swine pathogens are viruses, many of which may be transmitted to humans by direct contact or by indirect transmission pathways. In this study, the prevalence of astrovirus (AstV), group A rotavirus (RVA), norovirus (NoV) and hepatitis E virus (HEV) infections in pigs was investigated. During 2012-2014, 242 fecal samples were collected from pigs at different production stages (5 to 220 days old) on eight swine farms located in northern, central and southern Italy. Seven out of eight farms analyzed were positive for AstV, which was detected in 163 out of 242 (67.4%) samples and was the most prevalent virus; 61 of the 163 AstV-positive animals (37.4%) had diarrhea. HEV was detected on six farms and in 45 (18.6%) of the 242 samples analyzed. Twenty-three HEV-infected pigs had diarrhea (51.1%). A lower prevalence was observed for RVA, which was found in 10 of the 242 samples (4.1%) from three positive farms, and diarrhea was present only in six infected pigs (60.0%). No swine samples were found to be positive for NoV. Genetic diversity and phylogenetic relationships of some strains representative of the different viruses detected were investigated, confirming a wide heterogeneity of viral strains circulating among pigs.

Characterization of St-Valerien-like virus genome detected in Japan

A novel calicivirus, St-Valerien-like virus (SVV), has been identified in asymptomatic swine in Canada, Italy and the U.S.A. In this study, we characterized a new SVV strain (NUP-24/JP) detected in fecal samples of swine in Japan. The NUP-24/JP genome had 6,409 nucleotides and 2 open reading frames (ORF1 and ORF2). ORF1 and ORF2 consist of 5,940 and 453 nucleotides, respectively. Phylogenetic analysis revealed that NUP-24/JP was closely related to other SVV strains, particularly to U.S.A. strain NC-WGS93C/US. This finding suggests that SVV is prevalent in swine worldwide. Using a baculovirus expression system, we successfully produced virus-like particles, which would be useful for seroepidemiological studies of SVV.

Detection and characterization of potentially zoonotic viruses in faeces of pigs at slaughter in Germany

Pigs can harbour a variety of viruses in their gastrointestinal tract. Some of them are closely related to human viruses and are therefore suspected to have a zoonotic potential. Only little is known about the presence of those viruses in pigs at slaughter. However, by contamination of meat with zoonotic viruses during the slaughtering process, food-borne transmission to humans may be possible. Here we analyzed 120 faecal samples of pigs at slaughter from 3 different geographical regions of Germany for the presence of astrovirus (AstV), encephalomyocarditis virus (EMCV), hepatitis E virus (HEV), norovirus genogroup II (NoV GII) and group A rotavirus (GARV). Using real-time RT-PCR, the most frequently detected virus was AstV, which was present in 20.8% of the samples, followed by NoV GII with a detection rate of 14.2%. EMCV, HEV and GARV were found only occasionally with detection rates of 4.2%, 2.5% and 0.8%, respectively. Analyses of partial genome sequences of the viruses indicated that the detected AstV and NoV GII mainly represented typical pig virus strains, which have not been detected in humans so far. However, the GARV and HEV strains were more closely related to human strains. The results indicate that enteric viruses, some of them with zoonotic potential, are present in pig faeces at slaughter. Application of good hygiene practice is necessary to minimize the risk of introducing these viruses into the food and to prevent virus transmission to highly exposed persons such as slaughterers and veterinarians.

A review of known and hypothetical transmission routes for noroviruses

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII.4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed.

Development and application of a SYBR green RT-PCR for first line screening and quantification of porcine sapovirus infection

BACKGROUND

Sapoviruses are single stranded positive sense RNA viruses belonging to the family Caliciviridae. The virus is detected in different species including the human and the porcine species as an enteric pathogen causing asymptomatic to symptomatic enteritis. In this study, we report the development of a rapid real time qRT-PCR based on SYBR Green chemistry for the diagnosis of porcine sapovirus infection in swine.

RESULTS

The method allows the detection of porcine sapoviruses and the quantification of the genomic copies present in stool samples. During its development, the diagnostic tool showed good correlation compared with the gold standard conventional RT-PCR and was ten-fold more sensitive. When the method was applied to field samples, porcine noroviruses from genogroup 2 genotype 11b were also detected. The method was also applied to swine samples from the Netherlands that were positive for PoSaV infection. Phylogenetic results obtained from the samples showed that PoSaV sequences were genetically related to the currently described genogroup III, to the proposed genogroup VII and also to the MI-QW19 sequence (close to the human SaV sequences).

CONCLUSIONS

A rapid, sensitive, and reliable diagnosis method was developed for porcine sapovirus diagnosis. It correlated with the gold standard conventional RT-PCR. Specificity was good apart for genogroup 2 genotype 11b porcine noroviruses. As a first line screening diagnosis method, it allows a quicker and easier decision on doubtful samples.

Development of an optimized method for the recovery of infectious F-RNA coliphage MS2 from meat

F-RNA coliphages, part of the gut flora and likely to be deposited on meat along with other enteric organisms during carcass dressing and processing, may be regarded as an indicator and/or surrogate for potential zoonotic enteric viruses. There is no recommended sampling method for viruses on meats and there is a lack of information on the attachment of enteric viruses or F-RNA coliphages to gauze swabs, cellulose sponges and muscle and fat tissue. The objective of this work was to optimize the recovery of MS2 from muscle and fat tissue of meat by comparing phosphate buffered saline (PBS), 10% beef extract pH 7.2, and tryptose phosphate (2.9%) glycine (6%) broth pH 9.5 as eluants. The sampling techniques of excision, swabbing with gauze or cellulose sponges were compared with homogenizing the inoculated entire muscle or fat surface area. The recovery of MS2 from cellulose sponges using beef extract was significantly higher (P=0.001) than tryptose phosphate glycine broth which was significantly higher (P=0.0001) than PBS. There was no significant difference in the recovery between tryptose phosphate glycine broth and beef extract (P=0.92) and there was no significant difference between PBS and beef extract (P=0.10) when MS2 was recovered from gauze. No significant differences were observed between the different eluants with muscle tissue (P=0.91). When MS2 was recovered from muscle tissue with beef extract significant differences were observed (P=0.002); the sampling techniques of homogenizing the entire sample (56%) was equal to excision (43%) (P=0.23) and swabbing with a cellulose sponge (38%) (P=0.06) which were significantly higher than swabbing with gauze (28%), a second grouping of means indicated that homogenizing the entire sample was significantly higher than the other three sampling techniques. When MS2 was recovered from fat, significant differences were observed (P=0.000); homogenizing the entire sample (78%) was equal to excision (74%), which were significantly higher than swabbing with gauze (49%) or cellulose sponge (29%). The recovery of MS2 from meat is affected by the sampling technique. When choosing a nondestructive sampling method such as a cellulose sponge, a higher recovery can be obtained with beef extract as an eluant.

Emerging swine zoonoses

The majority of emerging infectious diseases are zoonotic in origin. Swine represent a potential reservoir for many novel pathogens and may transmit these to humans via direct contact with live animals (such as swine farmers and large animal veterinarians), or to the general human population via contaminated meat. We review recent emerging microbes associated with swine and discuss public health implications.

Seroepidemiology of porcine enteric sapovirus in pig farms in Venezuela

Porcine enteric sapovirus (PES) has been shown to cause diarrhea under experimental conditions in gnotobiotic piglets. However, the role of PES as enteric pathogens in porcine farms remains unclear. To further understand the PES-host interactions under field conditions, a serological survey was carried out. To this end the capsid gene of a PES isolate was cloned in the baculovirus expression system and an ELISA was developed based on virus-like particles from the baculovirus-expressed PES capsid protein. A total of 85 serum samples collected from pigs ranging from 8 weeks to over 54 weeks of age were analyzed. An overall seroprevalence to PESs of 62% was found, with significant differences (p<0.05) found between ages. Pigs younger than 10 weeks old and older than 12 weeks old showed high seroprevalences (70-100%), while pigs aged 10-12 weeks showed no detectable serum antibodies levels. Our results suggest that PES infections are common in pigs and that passively acquired maternal antibodies are soon replaced by actively acquired antibodies, whose titers increase gradually with age and that probably are maintained during lifetime.

First detection of porcine norovirus GII.18 in Latin America

Human (Hu) noroviruses (NoVs) circulate worldwide infecting people of all ages in developing and developed countries. Animal NoVs present some antigenic and genetic relationship to HuNoVs, although their zoonotic potential has not been established yet. Among animal NoVs, porcine (Po) NoVs are the most genetically related to HuNoVs. PoNoVs have only been detected in healthy finisher pigs in a few developed countries. Information about them lacks in developing countries. In this study 96 fecal samples from pigs of different ages from five farms in Rio de Janeiro State, Brazil were tested for NoVs. We report detection and genotyping by RT-PCR, nucleotide sequencing and phylogenetic analysis of partial polymerase and capsid regions of viral genome PoNoV genogroup II genotype 18 (GII.18) in one stool sample from a healthy finisher pig. This is the first report of PoNoV detection in Latin America and it supports the assumption that PoNoVs present a worldwide distribution.

Molecular characterization and phylogenetic analysis of the complete genome of a porcine sapovirus from Chinese swine

Background

Porcine sapovirus was first identified in the United States in 1980, hitherto, several Asian countries have detected this virus. In 2008, the first outbreak of gastroenteritis in piglets caused by porcine sapovirus in China was reported. The complete genome of the identified SaV strain Ch-sw-sav1 was sequenced and analyzed to provide gene profile for this outbreak.

Methods

The whole genome of Ch-sw-sav1 was amplified by RT-PCR and was sequenced. Sequence alignment of the complete genome or RNA dependent RNA polymerase (RdRp) gene was done. 3' end of ORF2 with 21-nt nucleotide insertion was further analyzed using software.

Results

Sequence analysis indicated that the genome of Ch-sw-sav1 was 7541 nucleotide long with two ORFs, excluding the 17 nucleotides ploy (A) at the 3' end. Phylogenetic analysis based on part of RdRp gene of this strain showed that it was classified into subgroup GIII. Sequence alignment indicated that there was an inserted 21-nt long nucleotide sequence at the 3' end of ORF2. The insertion showed high antigenicity index comparing to other regions in ORF2.

Conclusion

Ch-sw-sav1 shared similar genetic profile with an American PEC strain except the 21-nt nucleotide at the 3' end of ORF2. The insert sequence shared high identity with part gene of Sus scrofa clone RP44-484M10.

Incidence, diversity, and molecular epidemiology of sapoviruses in swine across Europe

Porcine sapovirus is an enteric calicivirus in domestic pigs that belongs to the family Caliciviridae. Some porcine sapoviruses are genetically related to human caliciviruses, which has raised public health concerns over animal reservoirs and the potential cross-species transmission of sapoviruses. We report on the incidence, genetic diversity, and molecular epidemiology of sapoviruses detected in domestic pigs in a comprehensive study conducted in six European countries (Denmark, Finland, Hungary, Italy, Slovenia, and Spain) between 2004 and 2007. A total of 1,050 swine fecal samples from 88 pig farms were collected and tested by reverse transcription-PCR for sapoviruses, and positive findings were confirmed by sequencing. Sapoviruses were detected in 80 (7.6%) samples collected on 39 (44.3%) farms and in every country. The highest prevalence was seen among piglets aged 2 to 8 weeks, and there was no significant difference in the proportion of sapovirus-positive findings for healthy animals and animals with diarrhea in Spain and Denmark (the only countries where both healthy animals and animals with diarrhea were tested). On the basis of the sequence of the RNA polymerase region, highly heterogeneous populations of viruses representing six different genogroups (genogroups III, VI, VII, and VIII, including potential new genogroups IX and X) were identified, with a predominance of genogroup GIII (50.6%). Genogroup VIII, found in five of the six countries, had the highest degree of homology (up to 66% at the amino acid level) to human sapovirus strains. Sapoviruses are commonly circulating and endemic agents in swine herds throughout Europe. Highly heterogeneous and potential new genogroups of sapoviruses were found in pigs; however, no "human-like" sapoviruses were detected.

Detection of porcine torovirus by real time RT-PCR in piglets from a Spanish farm

Toroviruses are enteric viruses belonging to the Nidovirales order that infect different animal species and humans. The lack of "in vitro" culture systems for toroviruses, except for the prototype Berne virus or BEV, isolated originally from an infected horse, has hampered their study and the development of diagnostic assays. This report describes a real time RT-PCR method to detect porcine torovirus (PToV) RNA in clinical fecal samples using primers corresponding to the gene coding for the nucleocapsid protein which are conserved in all PToV strains known to date. This method can be used to determine viral loads allowing quantitation within a range between 10(1) and 10(8) genomic units per reaction tube. The assay was evaluated with 48 rectal swabs from piglets from a Spanish farm. Nineteen out of 48 animals were shedding virus at the time of sample collection, indicating a high incidence of PToV infection in this farm. This is the first report showing the presence of PToV in Spain. The real time RT-PCR assay described in this report provides a rapid, highly sensitive, specific and reliable detection and quantitation method enabling future PToV epidemiological studies.

Molecular detection of kobuviruses and recombinant noroviruses in cattle in continental Europe

Two genotypes (Jena and Newbury2) and two intergenotype recombinant strains have been recognized in bovine noroviruses. Several studies have shown an apparent predominance of bovine infection with Newbury2-related (genotype 2) strains. Bovine stool samples were screened with two primer pairs targeting both the polymerase and the capsid genes. Among the predominant genotype 2 sequences, two were genetically related to the recombinant strain Thirsk10. The detection of sequences genetically related to Thirsk10, together with the very low rate of detection of Jena-related sequences, characterized the bovine norovirus population in Belgium, a representative region of continental Europe. Unexpectedly, bovine kobuvirus-related sequences were also amplified, extending their distribution area in Europe.

Molecular detection and prevalence of porcine caliciviruses in eastern China from 2008 to 2009

Caliciviruses causing diarrhea have been reported in both industrial and developing countries, including China, in recent years. Porcine caliciviruses that are closely related to human sapoviruses (SaVs) and noroviruses (NoVs) have also been detected in swine, which has raised discussion about the animal reservoir and the potential risk for zoonotic transmission to humans. The objective of this work was to determine the frequency and age distribution of SaVs and NoVs in pigs and to characterize the strains prevalent in eastern China. A total of 904 stool samples from pigs of different ages were collected from eastern China from April 2008 to March 2009 and tested for both SaVs and NoVs using reverse transcription-polymerase chain reaction (RT-PCR). Our results indicate that 8 (0.9%) stool samples were positive for SaVs and 2 (0.2%) for NoVs. Phylogenetic analysis of partial sequences of the RNA-dependent RNA polymerase (RdRp) gene indicated that all of the SaV strains belonged to the GIII SaVs, while the two NoV strains belonged to the GII NoV genogroup. The 8 SaV strains were further divided into two clusters, which clustered closely with the Netherlands isolate (AY615804) and the Chinese strain (EU599212), respectively. The two NoV strains shared about 67.3-67.6% nucleotide homology with a human norovirus strain (DQ369797), the only NoV strain from mainland China available in GenBank. Moreover, our results suggest that SaV infections are more frequent in 0-1 month-old pigs than in older ones. In conclusion, the present study provides evidence that PoSaVs and PoNoVs exist in swine in eastern China.

[First gastroenteritis outbreak caused by sapovirus (GI2) in Hungary - part of an international epidemic?]

Sapovirus belonging to Caliciviridae is one of the known pathogen of sporadic gastroenteritis infections in infants, children and rarely in elderly. Since the beginning of molecular monitoring of caliciviruses (mid 1990's) sapovirus was described rarely, once in approx. 5 years, as source of an outbreak. Circulation of caliciviruses has been monitored with molecular epidemiological methods by authors for 10 years in Hungary. Sapovirus has not been detected yet in the approximately 800 examined non-bacterial gastroenteritis outbreak. Based on the informal data supported by the international calicivirus surveillance study group, the number of outbreaks caused by sapovirus was increasing in Europe in 2008. Supposedly these outbreaks can be linked to genotype GI2 sapovirus.

AIMS

To describe the first verified detection and molecular epidemiological description of a gastroenteritis outbreak caused by sapovirus in Hungary.

MATERIALS AND METHODS

Stool samples originated from Bács-Kiskun County, from a mental deficiency day care center, where a gastroenteritis outbreak occurred in September, 2008. Amplification of the RNA polymerase gene of sapovirus was performed by RT-PCR method and the product was directly sequenced and phylogenetically analyzed. Clinical and epidemiological data were collected by epidemiological investigation.

RESULTS

17 of the 135 exposed people (12.6%) had gastroenteritis with vomiting and diarrhea in the period of September 11-22, 2008. Bacterial pathogens, rotavirus, adenovirus and norovirus were not detected, but sapovirus could be identified in 1 out of the 4 (25%) stool samples. The source of the outbreak was presumably the ill nurse and the virus spread with direct contact among the mentally deficient patients. Based on the RNA polymerase gene region the virus belongs to genotype GI2 sapovirus.

CONCLUSIONS

This study reports on the first detection of sapovirus from gastroenteritis outbreak in Hungary. Epidemiologic and clinical characteristics of the outbreak in the mental deficiency day care center are described in details to prove that not every case is "calicivirus" infection and epidemic is caused by the norovirus, which is another calicivirus examined by diagnostic methods. The outbreak caused by genotype GI2 sapovirus might be the part of an international epidemic, extended into a larger geographic area.

Self-assembly of the recombinant capsid protein of a swine norovirus into virus-like particles and evaluation of monoclonal antibodies cross-reactive with a human strain from genogroup II

Noroviruses (NoVs) are responsible for the majority of gastroenteritis outbreaks in humans. Recently, NoV strains which are genetically closely related to human genogroup II (GII) NoVs have been detected in fecal specimens from swine. These findings have raised concern about the possible role of pigs as reservoirs for NoVs that could infect humans. To better understand the epidemiology of swine NoVs in both the swine and the human populations, rapid immunoassays are needed. In this study, baculovirus recombinants were generated to express the capsid gene of a swine NoV GII genotype 11 (GII.11) strain which self-assembled into virus-like particles (VLPs). Subsequently, the purified VLPs were used to evoke monoclonal antibodies (MAbs) in mice. A panel of eight promising MAbs was obtained and evaluated for their ability to bind to heterologous VLPs, denaturated antigens, and truncated capsid proteins. The MAbs could be classified into two groups: two MAbs that recognized linear epitopes located at the amino-terminal half (shell domain) of the swine NoV GII.11 VLPs and that cross-reacted with human GII.4 NoV VLPs. The other six MAbs bound to conformational epitopes and did not cross-react with the human GII.4 VLPs. To our knowledge, this is the first report on the characterization of MAbs against swine NoVs. The swine NoV VLPs and the MAbs described here may be further used for the design of diagnostic reagents that could help increase our knowledge of the prevalence of NoV infections in pigs and the possible role of pigs as reservoirs for NoVs.

Molecular detection of norovirus in sheep and pigs in New Zealand farms

Human norovirus (NoV) is reportedly the major cause of non-bacterial gastroenteritis outbreaks worldwide and is commonly associated with water- and food-borne transmission via the faecal-oral route. Aside from humans, norovirus has been detected in pigs, cattle and mice. The close relatedness of some human and animal noroviruses has raised concerns about potential zoonotic transmission. Our laboratory recently reported the development of a multiplex real-time RT-PCR for the detection and genotyping of norovirus of genogroups I-III. Here we report a study of 56 faecal specimens from pigs and sheep that were collected and screened for noroviruses using this assay. Norovirus was found in 2/23 (9%) of porcine specimens (all were genogroup II) and in 8/33 (24%) of ovine specimens (all were genogroup III). Samples tested positive for norovirus were verified by conventional RT-PCR with different primer sets. Genomes of representative porcine and ovine norovirus strains underwent partial sequence analysis (343 and 2045 bases, respectively). This is the first report describing norovirus in sheep.

High genetic diversity in RdRp gene of Brazilian porcine sapovirus strains

Sapovirus is one genus within Caliciviridae family that causes diarrhea in humans and animals. Sapovirus (SaV) has been classified into seven genogroups (GI to GVII). The GIII, GVI, and GVII, which prototype is Cowden, JJ681, and K7/JP strains, respectively, infect pigs. The objective of this study was to characterize wild-type Brazilian SaV strains from piglet stool samples and determine SaV infection frequency, age distribution and association with diarrheic disease. Stool samples from 113 piglets up to 28-days-old were collected from 34 pig farms located in the States of Minas Gerais (MG), Mato Grosso do Sul (MS), Paraná (PR), Santa Catarina (SC), and Rio Grande do Sul (RS), during 2004 and 2005. The specimens were evaluated for enteric calicivirus by RT-PCR assay with primers p289/290, designed to detect the polymerase gene of SaV and norovirus. Thirty four (30.1%) samples were positive for SaV and five amplicons were sequenced. Phylogenetic analyses placed BRA29-MS/04 and BRA52-PR/05 sequences into the GIII of SaV genus. BRA04-SC/04, BRA21-RS/04, and BRA37-MG/05 demonstrated low identity with the Cowden strain but were closely related (up to 86.3%) to the Japanese and Dutch SaV strains, grouping together in a new cluster (GVIII?) in the phylogenetic tree. SaV infection was detected more frequently (p=0.0001) in animals between 22 and 28 days of age, in equal frequencies in piglets with and without diarrhea (p=0.59), and in the five Brazilian States. In this study, such as other unclassified worldwide SaVs, the Brazilian strains showed high genetic variability. Furthermore, the distribution and frequency of SaV infection provides evidence that the virus is circulating in Brazilian pig herds.

Detection and phylogenetic analysis of porcine enteric calicivirus, genetically related to the Cowden strain of sapovirus genogroup III, in Brazilian swine herds

Sapovirus of the Caliciviridae family is an important agent of acute gastroenteritis in children and piglets. The Sapovirus genus is divided into seven genogroups (G), and strains from the GIII, GVI and GVII are associated with infections in swine. Despite the high prevalence in some countries, there are no studies related to the presence of porcine enteric sapovirus infections in piglets in Brazil. In the present study, 18 fecal specimens from piglets up to 28 days were examined to determine the presence of sapovirus genome by RT-PCR assay, using primers designed to amplify a 331 bp segment of the RNA polymerase gene. In 44.4% (8/18) of fecal samples, an amplified DNA fragment was obtained. One of these fragments was sequenced and submitted to molecular and phylogenetic analysis. This analysis revealed high similarity, with nucleotides (87%) and amino acids (97.8%), to the Cowden strain, the GIII prototype of porcine enteric calicivirus. This is the first description of sapovirus in Brazilian swine herds.