الفهرس 
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Abstract
The objective of this study was to investigate the effect of glycyrrihizin (locally
isolated and purificated from licorice root) as an antiviral and immunostimulant
against duck hepatitis virus. In vitro study was carried out for investigation of the
cytotoxic effect and antiviral effect in different concentration and dilution of
glycyrrihizin on VERO cells and in vivo study was performed as 3 experiments on
220 ducklings divided into 4 groups were used as control, treated with glycyrrihizin,
vaccinated with live attenuated vaccine and other treated&vaccinated to investigate
the changes on blood picture, biochemistry, immunity and challenge test. The result
of in vitro investigation explained that glycyrrihizin has no toxic effect and has
antiviral effect till 106 dilutions. Also results of in vivo study revealed that duck
hepatitis virus (DHV) caused some clinicopathological (macrocytic hypochromic
anemia, leukopenia, hypoalbuminemia, hyperglobulinemia, hyperglycemia,
hypercholestrolenemia and marked elevation of liver enzymes and renal parameter)
and histopathological changes (focal hepatic necrosis infiltrated with mononuclear
inflammatory cells associated with bile ductal hyperplasia and vacuolation of the
lining epithelium of the renal tubules and pyknosis of their nuclei). Also, live
attenuated vaccine cause milder changes. Treatment with glycyrrihizin alone or in
combination with vaccine revealed good improvement of the concurrent changes
observed with infection or vaccine.