Genetic characterization and pathogenicity of a divergent broiler-origin orthoreovirus causing arthritis in China

Since 2013, there have been an increasing number of cases of arthritis in broilers caused by avian orthoreovirus (ARV) in China, and the virus remains highly virulent in chicks with high-level maternal antibodies. However, little information is available about the complete gene analysis and pathogenicity of the epidemic ARVs. In the study, the ARV strain (V-ARV-SD26) was isolated from broilers associated with arthritis in Shandong Province. To genetically characterize the ARV strain, the whole-genome sequencing was conducted by next-generation sequencing (NGS) technique. Sequence analysis demonstrated that V-ARV-SD26 might have acquired its current genomic composition through several homologous and, in case of the λC, μA and σB, divergent reassortment events. To further investigate the pathogenicity of the strain, 160 one-day-old Ross broilers with maternal antibodies were equally divided into four groups (foodpad-, eye mucosa- and intramuscular-inoculated groups and the negative control group), three experimental groups were inoculated separately with the low-dose virus fluid, and the negative control was equally inoculated with sterile PBS. The results showed that the symptoms of broilers in foodpad inoculation group were the most serious, while that of the eye mucosa infection group were the mildest. Meanwhile, the cloacal cotton swabs and organs were collected for qRT-PCR detection to evaluate the infection status. In conclusion, these findings indicate that V-ARV-SD26 is a divergent ARV strain, which provide experimental data for the prevention and control of newly emerged reovirus, and have a certain reference value for the preparation and evaluation of new vaccines.