Molecular diversity and detection of pestiviruses across ruminant species in Türkiye.

Pestiviruses have historically been described using host-associated disease names, such as Bovine Viral Diarrhoea Virus (BVDV) in cattle and Border Disease Virus (BDV) in small ruminants, and are important pathogens causing abortions, congenital anomalies, reproductive failure, and reduced productivity, resulting in substantial economic losses in livestock. This study investigated pestivirus infections in ruminant samples from Türkiye using serological and molecular methods, and RT-PCR-positive samples were further characterized by phylogenetic analysis. A total of 115 ruminant samples were collected from cattle (n = 76), sheep (n = 23), goats (n = 15), and buffalo (n = 1), including 85 samples collected in Türkiye and 30 whole-blood samples obtained from imported animals under quarantine. Antigen ELISA detected 34 positive samples, whereas RT-PCR identified pestiviral RNA in 61 samples. Molecular characterization was performed using primers targeting the 5'UTR, Npro, E2, and NS2-3 genomic regions. Phylogenetic analysis classified the 61 sequences into four pestivirus species: Pestivirus A [BVDV-1f (n = 32), BVDV-1 g (n = 4), BVDV-1 L (n = 7), and BVDV-1v (n = 1)], Pestivirus B [BVDV-2b (n = 1)], Pestivirus D (n = 4), and Pestivirus I (n = 12). Among the positive samples collected in Türkiye (n = 43), Pestivirus A, D, and I were identified, whereas imported animal samples (n = 18) contained Pestivirus A, B, and D. The detection of genetically diverse pestiviruses in both large and small ruminants indicates cross-host occurrence of multiple pestivirus species and subtypes in Türkiye. These findings expand current knowledge of the molecular diversity of pestiviruses circulating in ruminants in Türkiye and provide valuable data to support future surveillance, control, and eradication programs.