Molecular detection and epidemiological features of picobirnavirus in sheep and goat herds from southern Brazil

Picobirnaviruses (PBVs) are bisegmented double-stranded RNA viruses that have been detected in faecal samples from diverse hosts, but their epidemiology in small ruminants remains poorly understood. This study investigated PBV occurrence and epidemiological factors associated with detection in 405 animals (355 sheep and 50 goats) from nine herds in southern Brazil. Faecal samples were analysed by polyacrylamide gel electrophoresis (PAGE) and RT-PCR targeting PBV genogroup I (PBV-GI). PBV was detected in all nine herds and by either method in 173/405 (42.7%) animals, including 134/355 (37.7%) sheep and 39/50 (78.0%) goats.  Epidemiological analyses were restricted to sheep. After mutual adjustment, faecal consistency was not associated with PBV detection (adjusted odds ratio [aOR] = 0.73, 95% CI: 0.44-1.19; P = 0.207), whereas farming system showed an overall association (P = 0.012), with higher odds in subsistence than extensive systems (aOR = 2.68, 95% CI: 1.39-5.21). Leave-one-herd-out analyses supported the stability of the faecal-consistency result but showed that the farming-system association was sensitive to herd composition. Sequencing of 15 selected RT-PCR amplicons confirmed their identity as PBV, and BLAST analysis revealed heterogeneous closest sequence matches. To our knowledge, this is the first multi-herd epidemiological investigation of PBV in small ruminants in Brazil, demonstrating widespread viral detection and providing new insights into factors associated with PBV detection in sheep.