Infected nuclei were irregular to round in shape, greatly hypertrophied, and up to five
times normal size (Fig. 6). The strongly or weakly staining basophilic inclusions entirely occupied the nucleus and tended to be amorphous, though a finely granular structure could be seen occasionally. Scattered strands of nucleolar material were present in some of the inclusions. The earliest nuclear changes detected were a slight hypertrophy of the nucleus, a pale nucleolus or marginal nucleolar fragments, a thin marginal band of strongly basophilic chromatin, and infrequent fine eosinophilic granules scattered through a nonstaining nucleoplasm (Fig. 6). An intermediate
stage was represented by hypertrophied nuclei containing a single, pale purple-red to reddish
amorphous inclusion. These nuclei had a distinct margin of basophilic chromatin and a central nucleolus or circle of nucleolar remnants. The marginal chromatin stained strongly with the carbol fuschin counterstain in Gram’s stain. Inclusions in the advanced infections had a diffuse red reticulum throughout with the same stain. Inclusions did not stain with PAS, Giemsa, or
alcian blue and were Feulgen-negative. Virus-related nuclear pathology was only seen in the hepatopantreas.