Duck virus hepatitis
This highly contagious disease of ducks is caused by a member virus belonging to genus Enterovirus of the family Picornaviridae. It mostly affects ducklings below 3 weeks of age and is reported from coastal and duck rearing pockets of India. The disease is transmitted by ingestion of infected material. The vaccinated, clinically affected and recovered birds excrete the virus in large amounts in their feces for months.
Symptoms and lesions: With short incubation period of less than 24 h the clinical manifestations like depression, greenish diarrhoea are seen. Mortality may be up to
90% in ducklings below 7 days of age but in endemic areas, it may be as low as 10%.
Affected ducklings show enlarged and mottled liver showing hemorrhages, necrosis and cellular infiltration.
Diagnosis: The disease can be diagnosed on the basis of sudden onset and high
mortality in ducklings below 3 weeks with characteristic liver lesions. Virus isolation can be attempted from the liver, feces and whole blood by inoculating into embryonated eggs. About 60% of the infected embryos die within 5 days showing edema, stunted growth and greenish discoloration of the embryo fluid. The processed materials can be inoculated into susceptible day old ducklings. In positive cases the ducklings will die within 36 h after showing symptoms and lesions mentioned above. The confirmation is done by virus neutralization and detection of viral antigens in the liver, spleen by fluorescent antibody test.
Prevention and control: Introduction of new ducklings should be done with prior testing and general biosecurity measures. In endemic areas day-old ducklings can be vaccinated with egg-adapted live virus vaccine.