A fatal Pegosomum sp. (Trematoda: Echinostomatidae) infection in a wild cattle egret (Bubulcus ibis) from Japan.

An adult cattle egret (Bubulcus ibis) caught in Kobe of Hyogo Prefecture, Japan, in December 1995 died of a severe infection associated with the trematode parasite Pegosomum sp. At necropsy, 22 trematode parasites were found in the lumen of the bile duct, and the duct wall was markedly thickened. Histopathologically, severe cholangitis and cholecystitis were observed in close association with the parasites in the bile duct. Severe Pegosomum sp. infection may be one of the factors contributing to the mortality of wild cattle egrets. This is the first reported case of the genus Pegosomum infection in wild birds of Japan.