Fine structure of inclusion bodies in hepatic cells of chickens naturally affected with inclusion body hepatitis.

The fine structure of intranuclear inclusion bodies in the hepatic cells of chickens naturally affected with inclusion body hepatitis was studied comparing them with the inclusions seen with light microscopy. Ultra-structurally the inclusions were classified into two types depending on whether they contained virus particles or not. The first type consisted of virus particles, granular material and loose granular material, and sometimes concentric-circular lamellae enclosing the virus core. It is suggested that the virus particles are adenoviruses. This type corresponded to the basophilic inclusions seen with light microscopy. The second type was without virus particles and was subdivided into two forms, one consisting of fibrillar-granular material and the other of crystals composed of filaments. These corresponded to the eosinophilic inclusions seen with light microscopy. Eosinophilic inclusions were present in all 20 cases of inclusion body hepatitis, whereas the basophilic inclusions were present in only six. The presence of adenovirus particles might suggest that they are the aetiology of this condition, although they were present in only six of the 20 cases examined. The significance of the inclusions without viral particles was not adequately elucidated, but it was suggested they are degenerating material present in cells dying from the effects of the viral infection.