The pathology of Lates calcarifer herpesviral disease-Disseminated intravascular coagulation explains mortality spikes.

ABSTRACT

Lates calcarifer herpesvirus (LCHV) causes an emerging serious disease in aquaculture. Sudden drops in feed rates and mortality spikes exceeding 40%-50% often accompany LCHV infections in juvenile L. calcarifer, soon after transfer into sea cages. Affected fish have patchy white skin and fins, corneal opacity and frequently hang in surface water column like 'ghost' or 'zombie' fish. Fish have pale gills, fluid-filled intestines with yellowish casts, lipid depleted liver, enlarged spleen and kidney and reddened brain. Epithelial hyperplasia, apoptosis, marginated nuclear chromatin, amphophilic intranuclear inclusion bodies and the occasional multinucleated cells are observed in gills, skin, intestines, liver and kidney. These are often accompanied by lymphocytic-monocytic infiltration and extensive necrosis in gills, skin, kidney and intestines. Martius scarlet blue stains indicate presence of fibrin in vasculature in brain, gills, intestines, kidney and liver, or disseminated intravascular coagulation (DIC). DIC has been reported in human herpesviral infections. Multifocal lifting of intestinal epithelium with proteinaceous exudate and necrosis of several adjacent villi often progress to involve entire gut sections. Atrophied livers with accentuated lobules may progress to marked loss of hepatic acini. Multifocal dilated attenuated renal tubules are often accompanied by casts and marked protein loosing renopathy. This study on LCHV demonstrates that it can cause significant pathology and mortality.