Detection and molecular characterisation of noroviruses and sapoviruses in asymptomatic swine and cattle in Slovenian farms

Abstract

Acute infectious caliciviral gastroenteritis is a common illness in people all over the world. Two genera of the Caliciviridae family, Norovirus and Sapovirus, which usually cause disease in humans, can also be found in animals where they do not always cause clinical signs of gastroenteritis. To investigate the presence of norovirus (NoV) and sapovirus (SaV) strains in asymptomatic swine and cattle, a total of 525 faecal (406 pigs and 119 cattle) specimens were collected during 2004 and 2005 from 8 pig and 4 cattle farms geographically dispersed across Slovenia. RT-PCRs and sequencing were carried out using primers targeting RdRp and capsid regions of both NoVs and SaVs. NoV positivity was detected in both bovine (2/108 [1.9%]) and porcine (5/406 [1.2%]) faecal specimens while SaV positivity was present only in porcine (29/406 [7.1%]) specimens. All porcine NoV strains (n=5) detected were attributed to a single farm, while the porcine SaV strains (n=29) detected came from 5 different farms. Phylogenetic analysis of nucleotide sequences of partial RdRp fragments placed two of the bovine NoV strains in genogroup GIII. Of the 5 porcine NoV strains, 4 clustered with GII.11, while 1 strain showed the presence of GII.18. The majority [24/29, 82.7%] of the porcine SaV strains clustered in GIII within two separate lineages, while 5 strains clustered into recently identified genetic clusters GVII (3 strains), GVIII (1 strain) and unknown (1 strain), respectively. Although NoV and SaV strains in asymptomatic swine and cattle were detected at low levels, they were still phylogenetically placed in a common pattern within both genera showing great genetic variability. There were no detected human-like strains in this study.