Fasciolopsiasis results from an infection by the trematode Fasciolopsis buski,[1] the largest intestinal fluke of humans, growing up to 7.5 cm (3.0 in) long.

[2] The parasite infects an amphibic snail[3] (Segmentina nitidella, Segmentina hemisphaerula, Hippeutis schmackerie, Gyraulus, Lymnaea, Pila, Planorbis (Indoplanorbis)) after being released by infected mammalian feces; metacercaria released from this intermediate host encyst on aquatic plants like water spinach, which are eaten raw by pigs and humans.

The eggs are indistinguishable from those of the very closely related Fasciola hepatica liver fluke, but that is largely inconsequential since treatment is essentially identical for both.

Studies of the effectiveness of various drugs for treatment of children with F. buski have shown tetrachloroethylene as capable of reducing faecal egg counts by up to 99%.

[7] A study from 1950s found that F. buski was endemic in central Thailand, affecting about 2,936 people due to infected aquatic plants called water caltrops and the snail hosts which were associated with them.