Duck plague (duck virus enteritis)
Duck plague is the most serious disease caused by a herpes virus (Anatid herpes virus). Though antigenically homogenous, differences in virulence and some biochemical properties are observed among various isolates. The virus is relatively less stable and can be easily inactivated. Transmission is by direct and indirect contact mainly through water due to movement of infected birds. Transovarian transmission does not occur.
Symptoms and lesions: A sudden, high and persistent mortality in ducks of all ages
is an indication of duck plague. The birds may die in good condition. Nervous symptoms such as paralysis of the legs and wings, failure to swim in water, greenish diarrhea, lachrymation and depression are the clinical manifestations. In laying flocks the egg production is severely affected. The mortality rate varies from 10 to 90%. Breeder ducks show greater mortality than young birds.
PM lesions generally noticed are- the presence of blood in body cavities and
petechiae in various organs. The liver appears pale, copper coloured with petechiae and necrotic foci. Mucosal ulcerative eruptions in the gastro-intestinal tract and grayish white diphtheritic deposits in the mucosa of the esophagus are sometimes seen.
Diagnosis: The disease is diagnosed on the basis of the clinical signs, isolation and identification of the virus in CCL-141 cell line or duck embryo fibroblast and demonstration of viral antigens in the tissues by fluorescent antibody or ELISA tests.
Prevention and control: In India, vaccination with a modified live virus vaccine adapted in chicken embryo has been found to give good protection. This vaccine is usually administered subcutaneously to ducklings over 2 weeks of age.