The isolation and identification of a novel flavivirus from diseased Chinese soft-shelled turtle (Pelodiscus sinensis)

In recent years, mass mortality of Pelodiscus sinensis has occurred in many Chinese turtle farms and no etiological research on this disease has been conducted to date. The main clinical manifestation of sick P. sinensis was telangiectasis induced bleeding occurred in the limbs, calipash and plastron. After dissection, we found that the blood viscosity was reduced. Typical clinical manifestations included light abdominal cavity effusion, intestine and gastric wall edema and transparency. HE staining showed distinct lesions in liver, intestine, kidney, spleen, heart and lung tissues of infected P. sinensis. TEM observation showed that the spherical virions were approximately 30 nm in diameter. Partial genome of the pathogen was obtained by Illumina sequencing and then assembled and annotated. Phylogenetic analysis of the polyprotein amino acid sequences of this pathogen and other flaviviruses showed that it was closely related to Chinese soft-shelled turtle flavivirus isolate HZ-2017. RTPCR detection of this virus in the sick P. sinensis from turtle farms showed a high infection rate. QRT-PCR analysis of viral distribution in P. sinensis tissues indicated that the kidney contains the highest amount of virus. The virus was tentatively named "Pelodiscus sinensis flavivirus" (PSFV). In this study, the results of PSFV pathological characteristic and genome information laid a good foundation for further study of this virus.