Molecular epidemiology and histopathological study of a natural infection with decapod iridescent virus 1 in farmed white leg shrimp, Penaeus vannamei

• Published in: Aquaculture 2021-02, Vol.533, p.736105, Article 736105
• Main Authors: Qiu, Liang, Chen, Xing, Gao, Wen, Li, Chen, Guo, Xiao-Meng, Zhang, Qing-Li, Yang, Bing, Huang, Jie
• Format: Article
• Language: English
• Subjects: Cherax quadricarinatus iridovirus; Decapod iridescent virus 1; Decapodiridovirus; Lymphoid organ; Myoepithelial cell; Penaeus vannamei; Shrimp hemocyte iridescent virus
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2020.736105

As the only species of the new genus Decapodiridovirus within the family Iridoviridae, Decapod iridescent virus 1 (DIV1) has been proved to be the aetiological agent of the new disease, which causes mass die-offs of shrimp, prawn and crayfish. Samples of Penaeus vannamei were collected from three farms in Guangdong Province of China. Diseased P. vannamei exhibited the symptoms of hepatopancreatic atrophy with color fading, empty stomach and guts, obvious reddish body, enlarged and deepened pigmentation spots on the shell and covert mortality. Samples from three diseased farms were collected and pathogen detection revealed that P. vannamei, Pomacea canaliculata and Plexippus paykulli samples were DIV1 positive. Major capsid protein (MCP) gene of DIV1 isolate 20190514 was amplified by PCR and sequenced and sequence alignment showed that complete MCP sequences of three DIV1 isolates (SHIV 20141215, CQIV CN01 and 20190514) were all 100% identical. Histopathological examination revealed eosinophilic inclusions and pyknosis in lymphoid organ, hematopoietic tissue, epithelium and hemocytes of P. vannamei. Blue signals of in situ digoxigenin-labeled loop-mediated isothermal amplification appeared in lymphoid organ, hematopoietic tissue, epithelium and hemocytes. Transmission electron microscopy of ultrathin sections showed that a large number of DIV1 particles were present in lymphoid organ and myoepithelial cells. This study adds to the evidence that DIV1 could infect lymphoid organ and myoepithelial cells of shrimp, revealing new target organs for such pathogen. •The evidence consistently confirmed that the farmed P. vannamei sampled in this study were infected with DIV1.•Evidence proved that DIV1 could infect lymphoid organ and myoepithelial cells of shrimp.•Reddish body, enlarged and deepened pigmentation spots on the shell and covert mortality were considered to be the important basis for on-site diagnosis for P. vannamei infection with DIV1.