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Abstract
One hundred and ten, one day old, Hubbard chicks were divided into four groups. Gp.(1) was the control (20 bird). Gp.(2) was vaccinated at the ages of 8 days (by Nobilis Strain D78) and 18 days (by IBD BLEN) via the ocular route of 20 birds. Gp.(3) was infected with 0.1ml virus suspension at a titer of 105.5 EID50 at the age of 27 days via the ocular route of 40 birds. Gp.(4) was represented by 30 chickens which were vaccinated as gp.(2) then infected as gp.(3). Blood samples were collected from five chickens in each group at the ages of 29,31 ,33 and 43 days for the determination of the leukogram and biochemical studies, besides running the immunological test (IHA). Finally, the chickens were sacrificed. Tissue specimens were collected from the liver, kidneys, spleen and bursa of Fabricius for histopathological examination.
The signs included anorexia, depression, ruffled feathers, trembling, prostration, fever and watery whitish diarrhea on the 2nd, 4th and 6th days post-infection (PI) in gps.(3&4). The mortality rate was 17.5% in gp.(3) and 10% in gp.(4). Most birds, which survived 6 day PI were normal till the end of the experiment. Neither signs nor mortalities were detected in gp.(2).