Seroprevalence of porcine coronavirus antibodies in Iberian pigs and wild boars from central-western Spain.

Abstract

Porcine coronaviruses (PoCoVs) are common etiological viral agents of enteric and respiratory disease in swine, but most epidemiological information derives from intensively managed herds. Data from outdoor systems and wildlife remain scarce, despite the potential role of free-range production and wildlife-livestock interactions in sustaining virus transmission. In southern Spain, the traditional Dehesa agroforestry system supports Iberian pigs that share space and resources with wild boars and other species, creating interfaces where cross-species circulation may occur. To address this gap, we assessed the seroprevalence of five PoCoVs, including porcine hemagglutinating encephalomyelitis virus (PHEV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), transmissible gastroenteritis virus (TGEV), and porcine respiratory coronavirus (PRCV), in Iberian pigs and wild boars from central-western Spain. A total of 260 Iberian pig sera and 564 wild boar sera collected between 2016 and 2020 were tested using indirect ELISAs for PHEV, PEDV, and PDCoV and a blocking ELISA for PRCV/TGEV. Antibodies to PHEV were highly prevalent in Iberian pigs (68.0%) and detected at lower levels in wild boars (22.6%), a pattern consistent with endemic exposure in domestic pigs and sporadic circulation in wildlife. PEDV antibodies were identified in 8.5% of Iberian pigs and 2.8% of wild boars, with higher prevalence in pigs during 2016 followed by a sharp decline, suggesting past but not ongoing activity. PDCoV antibodies were rare overall (3.1% in pigs, 2.6% in wild boars) but reached 41.6% in pigs from Cáceres in 2017-2018, indicative of a localized event. PRCV antibodies were widespread in Iberian pigs (67.3%), with higher prevalence in Badajoz compared to Cáceres, while wild boars showed rising seropositivity in Ciudad Real/Toledo by 2022 (up to 33.3%). No TGEV antibodies were detected in either host population, supporting the predominance of PRCV in the region. These findings demonstrate that PHEV and PRCV are enzootic in free-range Iberian pigs, while PEDV and PDCoV circulate at low levels, and wild boars are more likely incidental than reservoir hosts. The detection of antibodies in the absence of clinical outbreaks underscores the silent nature of PoCoV circulation in extensive systems and highlights the importance of integrating wildlife-livestock interfaces into surveillance and biosecurity strategies in Mediterranean production landscapes.