Background Norovirus (NoV) has emerged as one of the major causative agents of non-bacterial, food- and water-borne gastroenteritis in humans. NoVs, belonging to Caliciviridae, are classified into 6 genogroups (G), from GI to GVI, which are further subdivided into 30 genotypes. NoVs identified in human gastroenteritis cases belong to GI, GII and GIV. NoVs have also been isolated from several animal species, including pigs. Detection of human GII.4 NoV in swine faecal and retail raw meat samples has raised public health concerns about the zoonotic potential of porcine NoVs and the role of swine in the epidemiology of this infection, as possible source of new viral recombinant strains that can be dangerous for human. Currently, there are no data on the prevalence of Norovirus in Italy in pigs: the only case described is related to a Norovirus GII.11, identified in swine faecal sample in absence of gastrointestinal clinical signs. Methods Faeces were collected at slaughterhouse in 2017 in two regions of North-East Italy. Forty-six samples originated from Veneto and thirtythree from Friuli Venezia Giulia regions, were analysed for presence of Calicivirus. A two-step RT-PCR targeting the RdRP gene with p290-p110 primer pairs was used. Sanger sequence of the partial RdRP gene was conducted on samples presenting enough amount of the target amplified DNA. For NoV positive samples, a new primer pair was designed for amplification and molecular characterization of VP1 capsidic region. Phylogenetic analysis was carried out using the Maximum Likelihood method and Kimura two-parameter substitution model using PhyML software. Results Fourteen samples collected in Veneto region were positive by RT-PCR for Calicivirus. Nucleotide sequences of about 300bp were obtained from only two samples. BLAST analysis showed nucleotide similarity between 89% and 92% with swine NoV GII detected in Europe. Phylogenetic analysis of the RdRp gene showed that Italian strains belong to the GII.11 and cluster with other swine NoVs from Europe, Asia and South America. Complete VP1 nucleotide sequence was obtained from only one sample: BLAST analysis showed nucleotide similarity of about 88% with swine NoVs GII detected in Asia. Conclusion This study identified GII.11 NoVs in the swine population of NorthEast Italy, similarly to a previous report in 2011. Serological studies aimed at investigate presence of antibodies against GII.4 in selected swine farms are ongoing. The real distribution and the role of NoVs in swine need to be further investigated by proper sampling approach and full genome analysis.

Norovirus GII in faeces of healthy pigs in North-East Italy

Mario Forzan;Maurizio Mazzei;
2018

Abstract

Background Norovirus (NoV) has emerged as one of the major causative agents of non-bacterial, food- and water-borne gastroenteritis in humans. NoVs, belonging to Caliciviridae, are classified into 6 genogroups (G), from GI to GVI, which are further subdivided into 30 genotypes. NoVs identified in human gastroenteritis cases belong to GI, GII and GIV. NoVs have also been isolated from several animal species, including pigs. Detection of human GII.4 NoV in swine faecal and retail raw meat samples has raised public health concerns about the zoonotic potential of porcine NoVs and the role of swine in the epidemiology of this infection, as possible source of new viral recombinant strains that can be dangerous for human. Currently, there are no data on the prevalence of Norovirus in Italy in pigs: the only case described is related to a Norovirus GII.11, identified in swine faecal sample in absence of gastrointestinal clinical signs. Methods Faeces were collected at slaughterhouse in 2017 in two regions of North-East Italy. Forty-six samples originated from Veneto and thirtythree from Friuli Venezia Giulia regions, were analysed for presence of Calicivirus. A two-step RT-PCR targeting the RdRP gene with p290-p110 primer pairs was used. Sanger sequence of the partial RdRP gene was conducted on samples presenting enough amount of the target amplified DNA. For NoV positive samples, a new primer pair was designed for amplification and molecular characterization of VP1 capsidic region. Phylogenetic analysis was carried out using the Maximum Likelihood method and Kimura two-parameter substitution model using PhyML software. Results Fourteen samples collected in Veneto region were positive by RT-PCR for Calicivirus. Nucleotide sequences of about 300bp were obtained from only two samples. BLAST analysis showed nucleotide similarity between 89% and 92% with swine NoV GII detected in Europe. Phylogenetic analysis of the RdRp gene showed that Italian strains belong to the GII.11 and cluster with other swine NoVs from Europe, Asia and South America. Complete VP1 nucleotide sequence was obtained from only one sample: BLAST analysis showed nucleotide similarity of about 88% with swine NoVs GII detected in Asia. Conclusion This study identified GII.11 NoVs in the swine population of NorthEast Italy, similarly to a previous report in 2011. Serological studies aimed at investigate presence of antibodies against GII.4 in selected swine farms are ongoing. The real distribution and the role of NoVs in swine need to be further investigated by proper sampling approach and full genome analysis.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/934307
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