Pigs are the main host of Seneca Valley virus (SVV), previously known as Senecavirus A (SVA). Pigs affected by SVV have vesicles in the nose, hooves, and limp and may cause death in some severe cases. Occasionally, SVV has also been detected in mice, houseflies, environmental equipment, and corridors in pig farms. Moreover, it was successfully isolated from mouse tissue samples. In this study, an SVV strain (SVA/GD/China/2018) was isolated from a buffalo with mouth ulcers in the Guangdong province of China using seven mammalian cell lines (including BHK-21, NA, PK-15, ST, Vero, Marc-145, and MDBK). The genome of SVA/GD/China/2018 consists of 7,276 nucleotides. Multiple-sequence alignment showed that SVA/GD/China/2018 shared the highest nucleotide similarity (99.1%) with one wild boar-origin SVV strain (Sichuan HS-01) from the Sichuan province of China. Genetic analysis revealed that SVA/GD/China/2018 clustered with those porcine-origin SVV strains. To the best of our knowledge, this is the first report of SVV infection in buffalo, which might expand the host range of the virus. Surveillance should be expanded, and clinical significance of SVV needs to be further evaluated in cattle.

Atypical porcine pestivirus (APPV) is an RNA virus newly discovered from swine in Asia, Europe, and the Americas. This novel virus has been confirmed as the cause of congenital tremor (CT) in piglets, which causes extensive economic losses to the swine industry. To investigate the genetic diversity and evolutionary relationship of APPV in China, 83 piglet samples with severe CT clinical signs were obtained from 12 commercial swine farms in 3 provinces of Southern China. RT-PCR revealed that the positive rates of APPV were as high as 100% (12/12) for the swine farms and 90.4% (75/83) for the samples. Subsequently, 21 positive samples and 3 positive samples were selected for partial E2 gene and complete polyprotein gene sequencing, respectively. Phylogenetic analysis showed that 62.5% of the sequences belonged to a novel APPV clade provisionally named genotype 3, which showed 81.0–82.1% sequence identity to genotypes 1 and 2. Amino acid sequence alignment showed that E2 protein of genotype 3 has three specific mutation sites, namely I19V, Y82F, and N107G. The results of the present study demonstrate that a novel APPV subgenotype, which is widely distributed in severe CT clinical samples in Southern China, was genetically diverse. We advocate for the inclusion of genotype 3 during revision of the APPV typing method.

Porcine reproductive and respiratory syndrome virus (PRRSV) has caused severe economic losses to the global swine industry. In recent years, the incidence of PRRSV-1 has been gradually increasing in China, but there are still few studies on it. In this study, clinical samples for PRRS virus isolation were collected from a pig farm in South China in 2022. We effectively isolated a strain of PRRSV utilizing PAM cells and demonstrated its consistent transmission capability on Marc-145 cells. The isolated strain was confirmed as PRRSV-1 by RT-qPCR, IFA, electron microscopy, etiolated spot purification and whole genome sequencing, the strain was named GD2022. The length of GD2022 genome is 15058nt; Based on the genome-wide genetic evolutionary analysis of GD2022, the strain was classified as PRRSV-1. Further genetic evolutionary analysis of its ORF5 gene showed that GD2022 belonged to PRRSV-1 subtype 1 and formed an independent branch in the evolutionary tree. Compared with the sequence of the classical PRRSV-1 strain (LV strain), GD2022 has several amino acid site mutations in the antigenic region from GP3 to GP5, these mutations are different from those of other PRRSV-1 strains in China. Recombination analysis showed no recombination events with GD2022. In addition, piglets infected with GD2022 displayed clinical respiratory symptoms and typical pathological changes. In this study, a strain of the PRRSV-1 virus was isolated using both PAM cells and Marc-145 and proved to be pathogenic to piglets, providing an important reference for the identification, prevention, and control of PRRSV-1.

Senecavirus A (SVA) is a critical pathogen causing vesicular lesions in sows and acute death of newborn piglets, resulting in very large economic losses in the pig industry. To restrict the transmission of SVA, an establishment of an effective diagnostic method is crucial for the prevention and control of the disease. However, traditional detection methods often have many drawbacks. In this study, reverse transcription loop-mediated isothermal amplification (RT-LAMP) was combined with a lateral flow dipstick (LFD) to detect SVA. The resulting RT-LAMP-LFD assay was performed at 60°C for 50 min and then directly judged on an LFD visualization strip. This method shows high specificity and sensitivity to SVA. The detection limit of RT-LAMP was 4.56x10^-8 ng/μL RNA, approximately 11 copies/μL RNA, and it was 10 times more sensitive than RT-PCR. This detection method’s positive rate for clinical samples is comparable to that of RT-PCR. This method is time saving and highly efficient and is thus expected to be used to diagnose SVA infections in this field.