Hepatitis E virus in young pigs in Finland and characterization of the isolated partial genomic sequences of genotype 3 HEV.

Hepatitis E virus (HEV) infections occur in swine worldwide. The porcine infection is usually subclinical, but HEV genotypes 3 and 4 are zoonotic agents that cause sporadic, indigenous human cases of hepatitis E. The aims of this study were to investigate the occurrence and dynamics of HEV infections in young pigs by analyzing a total of 273 fecal samples collected from six farrowing farms, to genetically characterize the HEV isolates obtained, and to examine the phylogenetic relationships of HEV isolates occurring at different swine farms in Finland. Fecal shedding of HEV of individual piglets was followed at two farms that were selected from five farms identified as HEV RNA positive. Excretion of HEV was detected in 87.5% of the piglets during the survey. Piglets contracted primary HEV infection 3-8 weeks after weaning, and at the time they were transferred to fattening farms, practically all (96.6%) of the pigs with a sample available at this occasion still excreted the virus. According to phylogenetic analysis, all HEV isolates obtained belonged to HEV genotype 3, subtype e, and a separate, farm-specific isolate originated from 10 of 11 farms examined. The results of our study show that HEV infections are highly common in young pigs, and HEV RNA-positive pigs enable HEV transmission from farrowing to fattening farms, creating a possible risk of infection for pig handlers, and that genetic variations in HEVs originating from different farms occur.