Tissue from 10 week old chicken (X100)
Description: Liver. The parenchyma is demonstrated with multifocal to coalescing areas of necrosis, granulomatous inflammation with multi-nucleated giant cells(MNGC), and single or clusters of round to ovoid 10-20 µm faint eosinophilic histomonads freely or within macrophages (see insert, lower right).
General: the free histonomads usually located within lacunes surrounded by a halo. In advanced lesion the histomonads are scant, difficult to recognized, and may appear as granular bodies within the lacune. The histomonads are strong PAS positive.
Morphologic Diagnosis: Sever, multifocal, granulomatous hepatitis with intralesional protozoa compatible with Histomonas.
Disease Diagnosis: Histomoniasis (Histomonas meleagridis). Dr Z. Raviv