Fig. 13.

Histopathology of infectious myonecrosis (IMN) shown in H&E stained sections (a–d) and by ISH with a IMNV-specific DIG-labeled probe (e). Mayer–Bennett H&E and DIG-labeled probe with Bismarck Brown counterstain; (a and b) Photomicrographs of sections through skeletal muscles in the abdomen of juvenile Litopenaeus vannamei with severe IMN. Hyaline necrosis of some muscle fibers in (a) is shown with marked edema among the affected fibers, as well as older lesions in (a) and (b) in which necrotic muscle has been infiltrated by hemocytes and replaced by fibrous tissue; (c and d) show large numbers of lymphoid organ (LO) spheroids (LOS) amongst normal LO tubules; (e and inset) photomicrographs of a LO with LOS that has been reacted in ISH with a IMNV-specific DIG-labeled probe. Parenchymal cells in the LO tubule walls show strong positive reactions for IMNV, and the high magnification inset shows that the virus is located in the cytoplasm of the infected cells.