Features of ORFs encoded by OYAV SZC50.

Biting midges are one of the most common hematophagous insects. They are capable of transmitting a wide range of arboviruses and have a significant impact on public health and veterinary medicine. Herein, from midge samples collected in 2013 in Yunnan, China, one sample induced a cell cytopathic effect (CPE) in BHK-21, MA104, and PK15 cell lines. Next-generation sequencing data, RACE and PCR determined the genome sequence of the sample and designated as an Oya virus (OYAV) isolate SZC50. Phylogenetic analysis of the sample revealed that it was cluster into viruses from species Orthobunyavirus catqueense. The open reading frames of S, M, and L segment of OYAV SZC50 were closest to those of OYAV SC0806. Moreover, 831 serum samples (736 pigs, 45 cattle, and 50 sheep) were gathered from 13 cities in Yunnan Province to detect neutralizing antibody of OYAV SZC50. A significant proportion of OYAV SZC50 antibody (more than 30%) was found in Yunnan pig populations, with the positive rate of OYAV SZC50 antibody in pigs from Malipo reaching 95%. To determine the pathogenicity of OYAV SZC50, we chose three animal models: specific pathogen-free Kunming mice, C57BL/6 mice lacking the interferon α/β receptor, and chicken embryos. At 5, 6, and 7 days post-infection, all adult and suckling C57BL/6 mice, and specific pathogen-free suckling Kunming mice were dead. Our finding was expanding the knowledge about the infection and pathogenic risk of the neglected virus in the Orthobunyavirus.