Bucephalid (Gasterostome) Cercariae Obtained from Freshwater Clams in Thailand

reshwater clams were collected in 16 sampling localities of 11 provinces in northeast Thailand. The clams were collected every 2 months, between February 2006 and August 2007, using the “counts per unit of time” sampling method. A total of 508 clam samples from 6 species were found–280 Corbicula sp, 23 Pilsbryoconcha sp, 136 Scabies crispate, 6 Pseudodon mouhoti, 51 Limnoperna siamensis, and 12 Physunio eximinus. Bucephalid (Gasterostome) cercariae were found from 3 clams belonging to 2 species, 1 Corbicula sp each at Rasi Salai and Lampao dams, and 1 Limnoperna siamensis at the Lampao River. The infection rate was 0.59% (3/508). Freshwater clams can serve as the first and second intermediate hosts for trematodes. This is the first study to report cercarial emergence from freshwater bivalves in this geographic region.