Haohao Lu, Min Zhang, Danjiao Yang, Xue Gao, Shuo Feng, Yiwen Pei, Zhidong Zhang, Long Zhou
Porcine teschovirus (PTV) is the causative agent of porcine diarrhea and multisystem disorder and poses a global threat to the health of domestic pigs. However, its epidemic and pathogenic characteristics in Tibetan pigs, which are a unique indigenous breed in the Qinghai-Tibet Plateau of China, remain largely unexplored. Here, we conducted a comprehensive investigation during 2024-2025, in which 303 diarrheic fecal samples were collected from 21 farms across eight counties in Ganzi Tibetan Autonomous Prefecture, with an average altitude of 3433 m. RT-PCR testing identified 141 PTV-positive samples, yielding a high positivity rate of 46.5% (141/303). From these positives, 27 VP1 sequences were cloned and sequenced; phylogenetic analysis revealed that 16 strains belonged to Teschovirus A, three strains were divided into Teschovirus B, and three strains formed the interspecies recombinant genotypes (PTV-15/16). Interestingly, five novel strains were classified as undefined genotypes, indicating an extensive genetic diversity among PTV strains circulating in Tibetan pigs. Furthermore, a PTV strain, designated PTV-SCgz-01, was successfully isolated in PK-15 cells, with a near-complete genomic sequence of 7081 nucleotides. Phylogenetic analysis based on the polyprotein and the VP1 genes indicated that it belonged to genotype PTV-4, whereas recombination analysis revealed that PTV-SCgz-01 is a natural recombinant with parental strains derived from HNMY (PTV-4) and China/SWU-ZG2/2018 (PTV-6). Experimental infection of 17-day-old Tibetan piglets demonstrated that this isolate induces severe watery diarrhea. Notably, the virus also caused severe pulmonary hemorrhage and mild cerebral hyperemia with neuronal degeneration, and it had a high mortality rate (40%), suggesting that strain PTV-SCgz-01 has strong pathogenic potential for 17-day-old Tibetan piglets. Our findings provide a more comprehensive molecular epidemiology of PTVs in Tibetan pigs and underscore the need for viral surveillance and control in this unique pig population.