Norovirus and sapovirus in pigs in Belgium

Noroviruses and sapoviruses belong to the norovirus and sapovirus genera respectively in the family Caliciviridae. These positive single stranded RNA viruses are known as common gastroenteritis agents in human and have been also identified in other species like swine (1). Porcine noroviruses and sapoviruses have been to date poorly detected in European countries. Porcine sapovirus have been only reported in 2 European countries, namely Hungary and Italy (2; 3) and porcine norovirus sequences were detected in The Netherlands (4).
In this study, both porcine noroviruses and sapoviruses were detected in swine stools showing their circulation in Belgian premises. Seven samples gave positive amplicons. Using BLAST and phylogenetic analysis, two porcine norovirus strains were identified and are genetically related to genotype 19 strains. Five samples contained porcine sapoviruses and are genetically related to the Porcine Enteric Calicivirus Cowden and newly described porcine strains. Sapovirus sequences were mainly detected in stool of piglets (less than 8 weeks old). Only one sequence was detected in an older pig (16-20 weeks). Norovirus sequences were detected in stools of fattening pigs (16-20 weeks). Neither sapovirus nor norovirus detected sequences could be associated with clinical signs of gastroenteritis.
In conclusion, the circulation of both porcine sapovirus and norovirus was shown in Belgium, extending their European distribution. Given uncertainties on the zoonotic risk, countries where swine and humans are relatively closed should develop surveillance programs where both human and animal calicivirus strains are screened in gastroenteritis outbreaks, wastewaters and veterinary diagnostic samples.