An unusual intracellular infection in ducks

An infection causing mortality was encountered on seven occasions in Muscovy (Cairina moschata) and domestic ducks (Anas platyrhynchos domestica). In all cases the principal lesion was a severe pneumonitis associated with the presence of numerous organisms in the cytoplasm of the blood capillary endothelial cells. Cultural examination for bacterial and fungal agents consistently failed to yield significant isolates. In tissue sections the organisms were poorly stained by haematoxylin and eosin but were strongly positive to the periodic acid-Schiff and periodic acid-silver methenamine methods. Electron microscopy showed round (0.5 microm to 1.0 microm diameter) or oval (1 microm x 1.7 microm) forms possessing a complex cell wall, cytoplasmic lamellar bodies and an apparently membrane-bound nuclear structure. On the available evidence, the identity of the organism and its classification as either a prokaryote or eukaryote were not resolved.