Phenotypic and genetic characterisation of an emerging reovirus from Pekin ducks in China

Yanxin Cao,Xueying Hu,Jun Wang,Weiyong He,Jingliang Su,Mengxu Sun

doi:10.1038/s41598-019-44178-3

Yanxin Cao, Xueying Hu + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-44178-3

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Abstract

In June 2016, a disease characterised by intestinal haemorrhage with a mortality rate of approximately 5% was observed in a duck farm in Shandong province, China. Here, we report the isolation and characterisation of a reovirus from duck tissue samples by inoculating duck embryos and duck embryo fibroblasts (DEF). The isolate replicated in DEF and Vero cells and formed syncytia. Sequence analysis revealed that the viral genome was 23,434 nt in length with typical structure organization, consisting of 10 dsRNA segments ranging from 3998 nt (L1) to 1190 nt (S4) in size, and was genetically distinct from previous Chinese duck-origin reoviruses. Phylogenetic analyses showed that the isolate was most closely related to the recently reported duck reovirus D2533/6/1-10 isolated in Germany, forming a monophyletic branch different from known reference avian reoviruses. Experimental infection results indicated that the isolate replicated transiently in ducklings and was shed via faeces. Infection with the isolate caused epithelial cell damage and lymphocyte apoptotic death in the bursa of Fabricius, which may result in immunosuppression in infected ducklings. The role of the isolate in current duck haemorrhage enteritis remains to be determined, but its damage to the bursa warrants further investigation of the duck immune response.

Highlights

Avian reoviruses (ARVs) are widely distributed in a variety of avian species, including wild birds[1,2,3,4]
No abnormal clinical signs were noted in ducklings infected by oral/intranasal or subcutaneous inoculation during the experimental period, and neutralising antibody was not detected in sera collected from the infected ducks on 9, 12 and 16 dpi
Differences in pathogenicity have been described for a number of avian reoviruses[6,7,21,22], and high morbidity and mortality with multifocal hepatic and spleen necrosis at necropsy have been recorded for the majority of duck and goose reovirus infections[9,10,11,13,15,23,24,25]

Summary

Introduction

Avian reoviruses (ARVs) are widely distributed in a variety of avian species, including wild birds[1,2,3,4]. They are members of genus Orthoreovirus in the family Reoviridae. ARVs have been associated with a variety of diseases in domestic fowl, including chickens (viral arthritis/tenosynovitis, malabsorption syndrome, gastroenteritis and respiratory disease)[6], turkeys (infectious enteritis)[7], ducks and geese (fatal infection and spleen necrosis)[8,9,10]. Since 2006, outbreaks of disease characterised by spleen necrosis in Pekin ducklings were observed, and the aetiological agent was identified to be a reovirus distinct from previous MDRV isolates[10]. Reovirus genetically distinct from previous duck reoviruses identified in China.

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