Trematode (Sphaeridiotrema globulus)-induced ulcerative hemorrhagic enteritis in wild mute swans (Cygnus olor).

Ulcerative hemorrhagic enteritis of swans induced by Sphaeridiotrema globulus is enzootic at Lake Musconetcong in northern New Jersey. It accounted for a calculated 250 deaths of wild mute swans (Cygnus olor) between 1970 and 1980. The swans died primarily in the winter and early spring. Sites of infection included the jejunum and ileum. Trematodes singly or in groups ulcerated the intestines. Severe hemorrhage from damaged submucosal capillaries provided a blood meal for the parasites and probably precipitated the anemia observed. The intensity of fatal infections ranged from 20 to 870 parasites. A mononuclear periportal hepatitis and secondary nodules in the spleen were commonly observed. Affected swans exhibited muscular weakness and appeared to have died from hypovolemic shock or some complication associated with it.