A male Cygnus olor and one cygnet which died (the latter after administration of an anaesthetic before pinioning) had clinical signs and lesions compatible with Dendritobilharzia infection. Histologic examination of the brain of both birds revealed disseminated granulomata in the cerebrum and cerebellum; the granulomata contained a centrally located schistosome egg. Similar granulomata were seen in the intestine of both birds. A mesenteric artery of the adult and an adrenal venule of the cygnet contained sections of adult trematodes. The adult had been maintained on an enclosed pond for 16 years; wild diving ducks are considered the source of infection.
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