Neoplastic Diseases in Poultry
337.338.Erythroblastosis (ER) is characterized by intravascular proliferations of immature precursors of erythrocytes. ER has a leukaemic character and is manifested with signs of severe anaemia. The liver and the kidneys are moderately enlarged with a characteristic dark red to mahogany colour, sometimes with haemorrhages.
339.ER is caused by the avian eryhtroblastosis virus (AEV); the most frequently encountered strains are E-26, ES4, R etc. The spleen is unusually enlarged or atrophied in cases of severe anaemia.
340.Histologically, accumulation of erythroblasts in blood sinusoids and capillaries is seen. The diagnosis is based on visceral histological lesions, typical for ER and peripheral blood haematological and morpho¬logical analysis.341.342.Osteopetrosis is a neoplastic disease, aetiologically related to the L/S group of viruses. It is characterized by a significant thickening of bone periosteum. The diaphyses of the tibia and/or tarsometatarsal bones are most commonly affected. Often, osteopetrosis is seen simultaneously with LL in the same bird.