Systemic hematological and metabolic shifts in grey mullet (Mugil cephalus) during low-grade lymphocystis disease virus (LCDV) infection: Insights from viral kinetics, whole blood biochemistry, and PCA

Abstract

Lymphocystis disease virus (LCDV) is a chronic, low-grade viral pathogen that affects a wide range of marine and freshwater teleosts. However, the systemic physiological responses of grey mullet (Mugil cephalus), a key aquaculture species in Korea, remain poorly understood. In this study, grey mullet were experimentally infected with LCDV and monitored for 60 days to assess viral kinetics, hematological alterations, and biochemical and metabolic changes, including multivariate profiling using principal component analysis (PCA). Viral DNA persisted at low levels (10^2 –10^4 MCP cop- ies/mg) throughout the experimental period. Hematological changes were mild but detectable, including transient lymphocyte elevation, temporary shifts in red blood cell indices (MCV and RDW), and decreases in platelet counts at multiple time points. Biochemical parameters showed early hep- atocellular stress (AST and ALT) and late-stage reductions in lipid- and protein-related markers, accom- panied by fluctuations in nitrogen metabolism. PCA effectively distinguished late-stage infection (30– 60 dpi) from early and control groups, driven primarily by decreases in lipid- and protein-associated variables. These findings demonstrate that even low-intensity LCDV infection induces measurable, stage-dependent physiological modulation in grey mullet and highlight the value of blood-based and multivariate analyses for assessing subclinical viral infections in aquaculture species.