Age and regional specific variation in seroprevalence of porcine circovirus 3 in the Japanese commercial swine population.

Abstract

Porcine circovirus 3 (PCV3) is globally distributed, yet its seroprevalence in the Japanese commercial swine population remains unknown. This study investigated the age-specific and regional variation of the seroprevalence of PCV3 in Japan. A total of 600 serum samples were collected from four major pig-producing prefectures (Kagoshima, Miyazaki, Gunma, and Chiba), stratified by four production stages: suckling, nursery, growing-finishing, and sows. Samples were analyzed using a capsid-based indirect ELISA. The overall seroprevalence was 15.3% (92/600), confirming widespread viral circulation. Significant geographical heterogeneity was observed (P&#x202f;<&#x202f;0.001), with positivity rates ranging from 1.7% in Gunma to 29.5% in Chiba. Age-specific analysis revealed that seroprevalence significantly increased with age (P&#x202f;<&#x202f;0.001). Seropositivity was low in suckling (5.3%) and nursery pigs (8.0%) but rose significantly in growing-finishing pigs (16.0%) and peaked in sows (32.0%). The high risk in sows (adjusted odds ratio = 9.78 vs. suckling) indicates that sows may contribute to maintaining PCV3 exposure at the farm level, while the rise in growing pigs indicates horizontal transmission. These findings imply a moderate seroprevalence level in Japanese commercial pigs compared to neighboring Asian countries.