الفهرس 
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Abstract
In Egypt, ducklings are exposed to fatal disease problems than induce high economic losses. The current study was concerned to investigate the role of DHAV as a causative agent of these losses.
Thirty two duckling flocks (2-11 days) were investigated during 2014-2015 in Sharkia Governrate. The results revealed depression, off food, ruffling feathers, lethargy, ataxia followed by opisthotonos (loss of balance falling on their sides and kick spasmodically) then death during one hour. Most of mortalities occurred at 2nd and 3rd days after showing signs. Mortality rates were up to 70% during the investigation period.
The gross lesions appeared mostly in the liver, which is enlarged and shows widespread petechial and/or ecchymotic haemorrhages. Also, spleen enlargement and swelling of the kidneys with some congestion of renal blood vessels were seen.
Histopathological picture of affected liver revealed hepatocyte necrosis (apoptosis), hydropic degeneration with varying degrees of extravasted erythrocytes in between the hepatic cells were seen. There were also aggregations of inflammatory cells around dilated central vein and in between hepatic cells.
Embryo inoculation results revealed delayed death of chicken embryos from 5 to 8 day post inoculation. This period is decreased by another virus passage in ECE. Examined embryos showed stunting in 16 flocks, subcutaneous hemorrhages covering the body and oedema in the hind limb and abdominal regions in 14 flocks, greenish allantoic fluid in 14 flocks, haemorrhage in embryonic liver in 14 flocks and greenish discoloration of liver in 7 flocks. The embryonic livers were enlarged and showed some necrotic foci in 14 flocks.