Taiwan study finds widespread hepatitis E exposure in fattening pigs

A new surveillance study suggests hepatitis E virus exposure is common in fattening pigs in Taiwan, with evidence of prior infection on most surveyed farms. Published September 9, 2026, in Frontiers in Veterinary Science, the cross-sectional study found 57.6% seroprevalence at the individual pig level and 90.6% farm-level positivity across 32 commercial farms in central and southern Taiwan. (frontiersin.org)

The findings matter because HEV is usually subclinical in pigs, but it remains a One Health concern. Domestic pigs are recognized reservoirs for zoonotic HEV genotypes 3 and 4, and Taiwan CDC states that genotype 4 strains have been identified in Taiwan and can infect both people and animals, including pigs. The agency also notes that undercooked pork, pork liver, and processed pork products are possible transmission routes, and cites local data showing higher HEV seroprevalence in pig farmers than in the general public. (frontiersin.org)

For this study, investigators collected 356 serum samples from pigs at early, middle, and late fattening stages on farms in Changhua, Yunlin, Chiayi, Tainan, and Pingtung during 2024 and 2025. Fifteen farms were sampled at more than one production stage. Overall seropositivity increased significantly with age: 44.4% in early fattening pigs, 58.8% in middle-stage pigs, and 66.5% in late-stage pigs. Compared with early-stage pigs, the odds of seropositivity were higher in middle-stage pigs and highest in late-stage pigs, supporting the authors’ conclusion that infection is commonly acquired before market age. (frontiersin.org)

The molecular results were more reassuring on the surface, but only to a point. Of the 356 serum samples, 274 had enough residual volume for RT-qPCR, and none were positive for HEV RNA. The authors caution that this likely reflects the short window for detecting viremia in serum rather than true absence of infection. In the discussion, they point to prior Taiwan research showing roughly 25% of slaughter-age pigs were HEV RNA-positive in feces, which means pigs may still be shedding virus or carrying it in tissues even when serum is negative. Broader reviews back that up, noting that HEV can persist in liver, bile, or feces and that slaughter-age infection remains a food safety concern. (frontiersin.org)

This study also updates a sparse local evidence base. A 1999 Taiwan study found 37% anti-HEV IgG seropositivity in 275 pigs from 10 farms and identified a close genetic relationship between swine and human HEV isolates in Taiwan, helping establish pigs as a plausible source of sporadic human infection there. The new paper reports a higher prevalence, though the authors note the older and newer studies used different serologic methods, so the increase shouldn’t be treated as a direct trend line without caution. (frontiersin.org)

Expert reaction specific to this paper was limited at publication, but the broader literature is consistent on the implications. Reviews and clinical guidance describe HEV genotypes 3 and 4 as zoonotic, emphasize elevated exposure risk in swine workers and veterinarians, and frame control as a farm-to-food-chain issue rather than a purely clinical one. Evidence from other countries shows that even when many pigs are only seropositive, a smaller share may still be viremic at slaughter, which is enough to keep food safety and occupational health on the table. (journal-of-hepatology.eu)

Why it matters: For veterinary professionals, especially those in swine practice, diagnostic labs, public health, and processing oversight, the paper is a reminder that serology and molecular testing answer different questions. High seroprevalence indicates widespread herd exposure, while negative serum PCR at a single time point doesn’t rule out active circulation or shedding. That has implications for surveillance design, biosecurity counseling, occupational risk communication, and conversations with producers about slaughter-age management and food safety. It also reinforces the value of One Health coordination between veterinarians, public health officials, and the pork supply chain. (frontiersin.org)

What to watch: The next meaningful step will be whether Taiwan researchers or animal health authorities expand surveillance beyond serum into feces, liver, bile, or slaughterhouse sampling, and whether genotype data are added to clarify how farm exposure patterns map to human risk. (frontiersin.org)