Background: Nowadays, immuno-stimulants have great importance in improving the immune system and minimising the effect of infectious diseases in poultry flocks. This study was designed to demonstrate the impact of using different immunestimulants on the reduction of the harmful implications of virulent ND virus through evaluation of histopathological lesion scores on bursa and trachea of vaccinated and infected broiler chickens with Newcastle disease (ND). Results: Eighty Ross breed broiler chicks at the age of 1 day were randomly divided into four groups, each group formed of 20 birds. Group I was vaccinated against AI, ND and IBD and used as a control. Groups II, III and IV were immunised as group I and also had immuno-stimulant supplement, Imutrix® (oregano oils plus ß-glucan), Evit liquid® (Vitamin E plus selenium) and Immunair 17.5 (Propionibacterium acnes and E. coli lipopolysaccharides), respectively. All groups were experimentally infected with virulent ND virus at the age of 28 days. The morbidity rates for groups I, II, III and IV were 15%, 5%, 5% and 10% respectively. Histopathological examination of bursa revealed hyperplasia of lymphoid follicles in group I which became more evident in groups II, III and IV. Group III showed hyperplasia of tracheal epithelium with lymphocytes and heterophils infiltration in lamina propria. CD79A-positive cells were significantly higher in bursa of group III in comparison to other groups during an immunohistochemical examination. Conclusion: It was concluded that Evit liquid® (vitamin E plus selenium) supplementation might have potent immunomodulatory effect in chickens.

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