Answer: giardia

AnswerCrossword Clue
giardiaany of a genus (Giardia) of flagellate protozoans inhabiting the intestines of various mammals and including one (G. lamblia syn. G. intestinalis) that is associated with diarrhea in humans
giardiaany flagellate of the genus Giardia, parasitic in the intestines of vertebrates
giardiaa protozoan inhabiting the intestines