Fig. 10.

Histopathology of white spot disease (WSD) shown in H&E stained sections (a and c) and by ISH with a WSSV-specific DIG-labeled probe (b and d). Mayer–Bennett H&E and DIG-labeled probe with Bismarck Brown counter stain; (a–d) photomicrographs of sections through the cuticular epithelium and subcuticular connective tissues of a small juvenile Litopenaeus vannamei with severe acute WSD. With H&E, haloed and eosinophilic (early or Cowdry type A) to darkly basophilic (mature) intranuclear inclusion bodies are abundant, and with ISH the inclusion bodies are generally dark blue–black due to reaction of WSSV with the DIG-labeled probe; and (e and f) TEM of a WSSV infected cell in the cuticular epithelium of a juvenile L. vannamei. The reason for the intense ISH-positive reaction in (b) and (d) for WSSV is evident due to the large number of WSSV virions present in the hypertrophied nucleus. Most of the virions are sectioned across their long axis and only a very few show the elliptical morphology of the intact virion. In (f), the dense central nucleocapsid and outer envelope of the virions is readily apparent.