Genetic Diversity of Porcine Circovirus Types 2 and 3 in Wild Boar in Italy

SIMPLE SUMMARY: Porcine circoviruses (PCVs) are major viral agents of farmed swine, causing relevant economic impact due to direct losses and control measures expenses. Wild boar may serve as a PCVs reservoir for the domestic pigs, thus threatening for production efficiency in pig farms. PCV infection in both domestic pigs and wild boar has been chiefly studied in Northern Italy, a densely populated area with a highly developed pork industry. However, data on circulation of PCV are scarce in other Italian areas. For the above reasons, along with the increasing sanitary relevance of wildlife as host of many livestock diseases, we carried out an epidemiological study to assess the prevalence and genetic characteristics of the PCVs circulating in wild boar in Basilicata region (Southern Italy), characterized by large forested areas with limited anthropic presence. A high prevalence was detected, suggesting that PCVs infection is endemic in the study population. These findings are of particular interest as the pig production system of the study area involves local breeds raised outdoor for the production of high-quality cured meat, thus having a high risk of being in contact with infected wild boar. ABSTRACT: Porcine circovirus (PCV) infection is associated with relevant economic impact to the pig industry. To date, four species of PCV (PCV1 to 4) have been identified but only PCV2 has been associated firmly with disease in pigs. The objective of this study was to assess the prevalence of PCV2 and PCV3 in the wild boar population in Basilicata region, Southern Italy, since this region is characterized by large forested and rural areas and the anthropic pressure is lower than in other Italian regions. Liver samples from 82 hunted wild boar were collected in 2021 from 3 different hunting districts. Sixty (73%, 95%CI: 63–82) samples tested positive for PCVs by quantitative PCR. In detail, 22 (27%, 95%CI: 18–37) were positive for PCV2, 58 (71%, 95%CI: 60–79) for PCV3, and 20 (24.4%, 95%CI 16–35) for both PCV2 and PCV3. On genome sequencing, different types and sub-types of PCV2 and PCV3 were identified, remarking a genetic diversity and hinting to a global circulation for the identified PCV strains. Overall, the high prevalence suggests that PCV2 and PCV3 infections are endemic in the wild boar population, posing risks for semi-intensive and free-range pig farming, typical of this region, due to contact with PCV-infected wild boar.