Duck plague
Duck plague, caused by a member of Herpesviridae, has world wide distribution and occurs among domestic and wild ducks, geese, swans and waterfowls.
Epidemiology: Major epidemics of duck plague are being from major duck breeding countries at regular intervals. The clinical features are anorexia, depression, ruffled feathers, photophobia, and extreme thirst, ataxia leading to recumbency, tremors and watery diarrhoea. Morbidity and mortality vary from 5 to 100%. Ducks showing clinical signs invariably die. On autopsy, extensive vasculitis, blood in body cavities including the GI tract, petechial haemorrhages on various organs are some of the pathological changes seen. Besides, diphtheritic plaques in esophagus, caecum, rectum, cloaca and bursa are also noticed.
Diagnosis: It is diagnosed by clinical signs, postmortem findings, mortality pattern and demonstration of intranuclear inclusion bodies in various organs. FAT is used for laboratory confirmation of the diagnosis.
Control: The disease can be effectively controlled by using chick embryo-adapted attenuated vaccine.
Duck hepatitis
Duck hepatitis, caused by an avian Enterovirus under the genus Enterovirus of Picornaviridae family, was first recognized in 1945 in ducks reared in Long Island, New York. There is only one serotype, and the natural history of virus is similar to that of avian encephalomyelitis virus. Goslings, turkeys and poults, chicks of guinea fowl and quails, but not chickens, are susceptible to experimental infection. The disease predominantly occurs in ducklings of less than 21 days of age. The disease runs a swift course, involving the entire flock within 3 days and resulting in almost 100% mortality. The affected birds exhibit certain typical clinical signs, viz. standing still with closed eyes, falling to one side, paddling spasmodically and dying in a few hours. The necropsy findings are mainly restricted to involvement of liver which is enlarged, oedematous and mottled with hemorrhages. Encephalitis with neuronal necrosis, gliosis and perivascular cuffing is present. The virus may be isolated in cell cultures or in 10 day old embryonated hen eggs (allantoic inoculation) . FAT is also used for early diagnosis of the viral antigen. Duck hepatitis needs to be differentially diagnosed from duck plague and Newcastle disease. Recovered ducks are immune. The disease is controlled by using attenuated, egg-adapted virus vaccine. Hyperimmune serum is helpful in saving in-contact birds and reducing losses during outbreaks.