Pathogenicity of duck origin virulent Newcastle disease virus strain in ducks

The pathogenicity of duck origin Newcastle disease virus(NDV)JSD0812 strain in ducks was investigated in this study.The median lethal dose(LD50)of virus-containing allantoic fluid in 15-day-old ducklings was 10-1.5/0.1mL.Experimental infections via intramuscular injection of 15,30,45,60,and 110 days old ducks showed that all infected ducks displayed overt clinical signs,but the mortality had a decreased tendency with increasing age,and no 110-day-old ducks died after infection.The infected ducks excreted infectious virus from the pharynx and/or cloaca for short periods.The percentage of virus isolation in tissues was generally low,even in those from died ducks.