Presence and shedding dynamics of Atypical Porcine Pestivirus (APPV) in semen of breeding boars: implications for virus transmission in pig production.

Abstract

BACKGROUND: Atypical porcine pestivirus (APPV), genus Pestivirus, is the causative agent of congenital tremor type A-II, a neurological disease in newborn piglets that is characterized by tremors. Although the virus can spread horizontally, clinical disease is observed only after in utero infection. While venereal transmission has been proposed as a potential route, the pathogenesis and transmission dynamics of APPV remain incompletely understood. In this study, we aimed to investigate the presence of APPV in semen from Norwegian breeding boars, its temporal shedding patterns, and the potential impact of APPV on semen producing organs. RESULTS: An initial screening of 110 breeding boars revealed that 50.9% (56/110) were APPV-positive in semen, as determined by reverse transcription quantitative PCR (RT-qPCR). The virus load in semen was highly variable, with concentrations up to 4.0 × 10^6 genomic copies (GC)/mL. Extended sampling of a smaller subset of APPV-positive boars (n = 19) revealed that virus shedding in semen typically persisted for less than 3 months, although intermittent shedding for up to 7 months was observed in one boar. At slaughter, the virus was detected in reproductive organs and accessory glands - even in boars with negative semen and serum samples - but it was not associated with histopathological lesions. CONCLUSIONS: As artificial insemination (AI) is widely used in all tiers of pig production, APPV-positive semen from breeding boars may represent an important source of virus transmission. To assess the viability of APPV in AI semen and clarify its potential role in transmission, further research, such as virus isolation for infectivity studies and experimental infections in naïve sows, are required.