Infectious myonecrosis virus (IMNV) and decapod iridescent virus 1 (DIV1) detected in Penaeus monodon from the Indian Ocean

Infectious myonecrosis virus (IMNV) was first discovered in the Americas in 2004 as a new lethal pathogen of cultivated whiteleg shrimp Penaeus vannamei, but infections were not lethal for the giant tiger shrimp Penaeus monodon. In 2007, it was reported in diseased P. vannamei cultivated in Indonesia but, until recently, not from other countries in Asia. Decapod iridescent virus (DIV1) was first reported from China in 2016 and is lethal for the crayfish Cherax quadricarinatus and Procambarus clarkii, for the penaeid shrimp P. vannamei and P. chinensis and for the palaemonid shrimp Macrobrachium rosenbergii and Exopalaemon carinicauda. It has not yet been reported from other Asian countries. Here we describe the occurrence of positive test results for IMNV and DIV1 using polymerase chain reaction (PCR) technology during screening of grossly normal, broodstock-size, wild P. monodon captured from the Indian Ocean and held in a biosecurity facility for screening. Amplicons for each virus were obtained from two widely separated targets in the relevant viral genomes listed at GenBank, and sequencing revealed 99-100% identity to the targets for each virus. Based on these results, the captured specimens were destroyed. The results raised the possibility that grossly normal, captured P. monodon might serve as potential vehicles for introduction of IMNV and/or DIV1 to shrimp hatcheries and farms. Thus, we recommend that appropriate precautions be taken to avoid this possibility.