Detection of infectious myonecrosis virus in Penaeus vannamei using the multiplexed PCR platform shrimp MultiPathTM

Infectious myonecrosis virus (IMNV) causes 40-80% cumulative mortality in Penaeid shrimp aquaculture, with severity being dependant on pathogen variant and culture conditions. With an increasing presence of IMNV in shrimp aquaculture and devastating impacts in recent years on commercial production, there is increased demand for cost effective surveillance, early detection, and early mitigation strategies for this pathogen in combination with other devastating pathogens including White Spot Syndrome virus (WSSV), virulent strains of Vibrio parahaemolyticus (which cause acute hepatopancreatic necrosis disease (AHPND)) and Enterocytozoon hepatopenaei (EHP) that are also highly prevalent around the world. This study undertook assay validation of the IMNV test within the commercially available Shrimp MultiPathTM (SMP) technology in comparison to an existing quantitative PCR recommended by the World Organisation for Animal Health (WOAH). A total of 254 samples from three Penaeus vannamei populations from farms in the Indo-Pacific region that had reduced feed intake were used for this study. Key performance metrics for analytical and diagnostic performance of the IMNV assay in Shrimp MultiPathTM were assessed in addition to reproducibility and repeatability following the WOAH validation pathway. Establishing these metrics is important to provide the global industry with a cost-effective reliable tool that can be used to look at complete pathogen profiles to mitigate disease risk in shrimp farming. Limit of detection was determined to be 6.6 copies per microlitre of total nucleic acid sample. The diagnostic sensitivity of the IMNV SMP was 99.2% and diagnostic specificity 98.0%, whereas the diagnostic sensitivity and specificity of qPCR were estimated to be 86.9% and 98.2%, respectively. Importantly, the SMP IMNV assay detects both Indo-Pacific and Eastern Latin American variants of IMNV. Overall, the IMNV SMP assay outperforms currently published assays for early detection, and early risk mitigation of this pathogen in shrimp culture, whilst having the added benefit of a full pathogen profile due to its multiplexed nature.