Fig. 7

Histopathological lesions in smallmouth bass (Micropterus dolomieu) infected with largemouth bass virus. a Extensive ulcerative dermatitis (arrowheads) with severe epithelial necrosis (asterisk). b Higher magnification of the affected epithelium with cytoplasmic swelling and vacuolation of epithelial cells (arrowhead), nuclear pyknosis (asterisk) and infiltration of heterophils (arrows). c Severe necrotizing myositis with necrotic myofibers (asterisk) being surrounded by extensive infiltrates of heterophils admixed with macrophages (arrowheads). d Ulcerative dermatitis was commonly associated with secondary colonization by bacteria (arrowheads) and fungal hyphae (arrow). e Severe necrotizing panuveitis with heterophilic and histiocytic inflammation expanding the choroid (asterisk) and extending into the sclera (S) and infiltrating the episclera. f Severe heterophilic vitritis with the vitreous chambers (V) containing large numbers of heterophils and fewer macrophages admixed with fibrin and hemorrhage