Unionidae is the most diverse family of freshwater bivalves; however, infectious diseases of these molluscs have received little attention. A total of 200 freshwater mussels from five species were collected monthly during the period of February 2016 to August 2017 from Tura region in River Nile, Cairo, Egypt during the current investigation. The collected samples consisted of 50 Corbicula fluminea, 50 Caelatura aegyptiaca, 50 Nitia teretiuscula, 30 Mutela rostrata and 20 Chambardia rubens. Mussels were dissected and examined for detection of parasitic infection. Larval trematodes were recovered from mussel species N. teretiuscula with infection rate 2% (4/200). Light and scanning electron microscopic examinations showed that the pre-patent invasions of trematode parasites belong to three families, Rhipidocotyle campanula (Bucephalidae), Phyllodistomum sp. (Gorgoderidae) and Echinostoma sp. (Echinostomatidae). Also, the histopathological effects associated with larval trematode infection were studied in different tissues of N. teretiuscula. No infection was demonstrated in the mantle and visceral mass. The present study indicated that freshwater mussels can serve as first and
second intermediate hosts for trematodes. In addition, this is the first study to report cercarial emergence from freshwater bivalves in this geographic region.