Pathology associated with a viral erythrocytic infection in turbot, Scophthalmus maximus (L.)

Abstract. Since 1992, frequent erythrocytic viral infections have occurred in cultured turbot, Scophthalmus maximus (L.), on several fish farms in Galicia, Spain, causing important mortalities. Affected fish showed haemorrhages in the head, mouth and fins, exophthalmia and abdominal distension. The disease was also characterized by the presence of pale blue inclusions in affected erythrocytes. The examination of these erythrocytes by electron microscopy showed virus particles of 50–160 nm in size in the cytoplasm, budding av the cell membrane and extracellularly. The histopathological study revealed occasional necrosis of kidney haematopoietic tissue, an increase in the size and number of melanomacrophage centres of the spleen and kidney, and oedematous areas with hepatocytes containing eosinophilc bodies in the liver. Degeneration of muscle fibres was accompanied by an intense inflammatory oedema. Dermatitis as well as uveitis and corneal oedema were consistent lesions.