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In mid-2020, using next-generation sequencing (NGS) technology, we identified a divergent cluster 2 avian orthoreovirus (ARV) variant named PHC-2020-0545, isolated from tendons of 33-day-old broilers with leg swelling in China. Sequence comparison and phylogenetic analysis of results revealed that the isolate strain was genetically distinct from all known ARV strains in M1 and M3 genes, and the σC coding gene was quite different from the identified ARV strains grouped into other genotyping cluster. The recombination analysis revealed that multiple segmental recombination, intra-segmental recombination and accumulation of point mutations might contribute to the emergence of this isolate. The broilers infected with the PHC-2020-0545 strain showed typical clinical symptoms of tarsal joint swelling, and the isolate mainly affected the movement, digestion and metabolism of broilers. Although the mortality of broilers caused by the isolate was very low, the results of viral load detection revealed that it had strong replication ability in vivo. In addition, the infection route of the isolate is related to its pathogenicity to broilers. Therefore, we determined that the PHC-2020-0545 field strain is a unique novel recombinant ARV strain, which might become prevalent in Chinese broiler flocks.

Since 2017, duck spleen necrosis caused by a new variant duck orthoreovirus (N-DRV) infection had been observed in many provinces in China. This disease causes the growth and development of ducks to be retarded, and the feed return rate is reduced. Because the target organ of the disease is mainly the spleen, the immune suppression of the diseased ducks is easy to secondary infection of other pathogens. In this study, we successfully constructed a breeding duck artificial infection model and found that N-DRV infection can cause pathological changes such as ovarian hemorrhage, follicle atrophy, and fallopian tube bleeding in breeding ducks, resulting in a significant reduction in the fertilization rate and hatching rate of breeding eggs. The qPCR method was used to detect viral RNA in samples of egg vitelline membrane, duck embryo, and duckling’s spleen. It was found that viral RNA was present in the above samples. Although there were no obvious clinical symptoms in the early stage of ducklings, autopsy revealed obvious pathological changes in the spleen and other organs. The sequence distance and phylogenetic analysis of the strain re-isolated from the spleen samples of ducklings (named N-DRV-SD19) confirmed that N-DRV-SD19 was consistent with the strain N-DRV-XT18 used for the infection of the breeding ducks. The findings of the above research confirmed that N-DRV can be vertically transmitted through eggs, which will provide an important reference for the prevention and control of the disease.

In order to explore the genetic mutations of the H9N2 subtype avian influenza viruses isolated in Shandong, sixteen avian influenza virus subtype H9N2 were isolated from different areas of Shandong Province. The complete HA fragments of the viruses were amplified by RT-PCR and the sequences were analyzed on homology and heredity evolution after the cloning and sequencing of the products. The results showed that the amino acid motif of cleavage sites for all the sixteen virus in the HA gene were RSSR decrease GLF, which was consistent with the characterization of the LPAIV. Seven to nine potential glycosylation sites were found during the analysis and the receptor binding sites were relatively conservative except the 198 site. The Leucine(L) at the amino acid position 234 in the HA genes of all isolates indicated the potential of binding with SAalpha,2-6 receptor of mammals. Homology analysis showed that the homology of HA nucleotide and amino acid sequences was 96.3%-99.9% and 97.1%-99.6% for different strains. They belonged to a branch of the A/Duck/Hong Kong/Y280/97 in the phylogenetic tree.

PCV-2 (Porcine circovirus type-2, PCV-2) and PRRSV (Porcine reproductive and respiratory syndrome virus, PRRSV) were detected by PCR from 253 porcine pleuropneumonia samples and 125 clinically healthy lung samples were collected from different districts of Shandong province. The results showed that 171 samples for PCV-2 and 101 samples for PRRSV were positive. The positive ratio were 67.5% and 40%, respectively. The co-infection number of PCV-2 and PRRSV was 68 in 253 samples, the positive ratio was 26.8%. While in the clinically healthy samples, only 21 samples for PCV-2 and 12 samples for PRRSV were detected positive, the positive ratio were 16.8% and 9.6%, respectively, no co-infection samples were found. Statistical result showed significant difference between positive ratio for PCV-2 and PRRSV in porcine pleuropneumonia samples and that of in clinically healthy samples. The above results demonstrated that there maybe some relationship between the infection of porcine pleuropneumonia and PCV-2 and PRRSV in pigs.