A new lineage of Ranavirus micropterus1 infects ornamental wrasses from the Great Barrier Reef and causes severe disease in captivity
The Great Barrier Reef (GBR) supports remarkable biodiversity, providing a variety of valuable ecosystem services. Yet it is among the most threatened ecosystems globally, and diseases affecting reef fishes remain poorly understood. We used a metatranscriptomic approach to investigate a disease outbreak in captive red leopard wrasses (Macropharyngodon choati) from the GBR characterised by abnormal swimming behaviour and impaired respiration with 100% mortality. Metatranscriptomic analysis identified a novel isolate of Ranavirus micropterus1, Macropharyngodon choati ranavirus (McRV), in all sample types with exceptionally high transcript abundance alongside the expression of host genes linked to cellular stress and immune function. Histopathology revealed multifocal necrosis of renal tubules, and cytopathic effect was observed in bluegill (BF-2) cells. Phylogenetic analysis placed McRV in a distinct clade of wrasse ranaviruses, clustering with another virus previously identified on the GBR, indicating that wild wrasses serve as natural hosts. These data illustrate the power of metatranscriptomics for disease investigation and emphasise the need for enhanced pathogen monitoring in marine wildlife increasingly threatened by anthropogenic change.