Giardia duodenalis is the most common protozoan cause of diarrhea in the world. A hallmark of this infection
is the variation in clinical responses which are observed, ranging from asymptomatic, self-limited infections to chronic
infections with persistent severe diarrhea, cramps, nausea and weight loss. Some of this variation likely derives from
differences in the parasites themselves, while the remainder is likely due to differences in host immune responses. This
chapter will focus on the role of immune responses in determining the outcome of infections with Giardia, both in
eradicating parasites from the intestinal lumen and in contributing to the symptoms of infection.
