Duck virus enteritis (anatid herpesvirus infection) in mute swans (Cygnus olor).

An outbreak of duck virus enteritis (DVE) in mute swans (Cygnus olor) is described. Ninety-nine captive swans in a flock of 440 died within 3 months. The origin was obscure. The infection did not spread to other species on the same premises. Clinical signs included polydypsia, photophobia, inappetance, drooping wings, watery nasal discharge and yellowish diarrhoea. Necropsies were made on eight swans. All showed a diphtheritic oesophagitis especially near the oesophageal-proventricular junction. Whitish, necrotic plaques from 1 mm to 3 cm in extent affected the epithelium of the small intestine. Other lesions were present but less consistent. Histological examination of livers showed typical lesions of DVE associated with intranuclear inclusions. The virus was propagated in duck kidney cell cultures and on second passage caused a cytopathic effect with intranuclear inclusions typical of DVE. Presence of virus was confirmed by electron microscopy. Experimentally the virus infected susceptible, unvaccinated ducklings, but not those vaccinated against DVE.