Fig. 7.

Histopathology of Taura syndrome (TS) is shown in H&E stained sections (a, b, e, and g) and by ISH with a TSV-specific DIG-labeled probe (c, d, f and h). Mayer–Bennett H&E and DIG-labeled probe with Bismarck Brown counterstain; (a–d) photomicrographs of sections through the cuticular epithelium of small juvenile Litopenaeus vannamei with severe acute TS. Prominent foci of necrosis of the cuticular epithelium (thick arrow in a) are shown between normal appearing patches of cuticular epithelium (thin arrow in a); (b–d) higher magnification views of TSV lesions (by H&E and ISH) in the cuticular epithelium showing characteristic necrotic cuticular epithelial with pyknotic and karyorrhectic nuclei, a generally increased cytoplasmic eosinophilia in intact cells, and very numerous, variably staining, spherical remnants of cytoplasm from disrupted cells. The cytoplasmic remnants, pyknotic and karyorrhectic nuclei give the lesion a pathodiagnostic “peppered” or “buckshot-riddled” appearance. The acute nature of the lesion is suggested by the absence of hemocytes in or near the lesion. Demonstration of TSV by ISH with a DIG-labeled probe is shown in (c), (d), (f), and (h). In (c) and (d), TSV is shown in the cytoplasm of still intact cuticular epithelial cells in areas presenting the “buckshot-riddled” appearance that is pathognonomic for TSV acute-phase lesions; (e and insert) low and higher magnification views of a resolving TSV lesion in the cuticular epithelium. The former TS lesion is now in the “wound-healing” process and is marked by multiple layers of melanized and un-melanized hemocytes which have closed the lesion and are providing a foundation for ingrowth of fibrocytes and normal cuticular epithelium from unaffected adjacent areas. A surface plaque of bacteria is shown colonizing the apical surface of the resolving lesion; (f and insert) ISH preparation of the lymphoid organ in which the distal parenchymal cells of the lymphoid organ are accumulating large amounts TSV from the circulating hemolymph during the late acute or transition phase of TS; (g and h) parallel sections (H&E and ISH) of the lymphoid organ (LO) of an experimentally infected L. vannamei in the chronic phase of TS several months after infection. With H&E LO spheroids (LOS) are the only lesion apparent in shrimp in the chronic phase of TS, but the parallel section reacted in ISH with a TSV-specific probe shows the presence of the TSV-infected cells in these LOS. Mayer–Bennett H&E and DIG-labeled probe with Bismarck Brown counter-stain.