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

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.

Automated summary

As the sole species of the new genus Decapodiridovirus in the family Iridoviridae, Decapod iridescent virus 1 (DIV1) has been identified as the causative agent of a new disease leading to mass mortalities of shrimp, prawn and crayfish. A study in Guangdong Province of China found that DIV1 could infect lymphoid organ and myoepithelial cells of shrimp, expanding the knowledge on target organs for this pathogen.