Which one of the following is true about Giardia?
**Core Concept**
Giardia is a protozoan parasite that causes giardiasis, a waterborne disease affecting the small intestine. The parasite adheres to the intestinal mucosa, leading to malabsorption and diarrhea.
**Why the Correct Answer is Right**
Giardia trophozoites have a unique ability to adhere to the intestinal mucosa using a surface protein called variant-specific surface protein (VSP). This adhesion leads to the formation of a cystic structure, which protects the parasite from environmental stress and facilitates its transmission through contaminated water. The parasite's adherence to the mucosa causes inflammation, leading to malabsorption and diarrhea.
**Why Each Wrong Option is Incorrect**
* **Option A:** Giardia is not typically transmitted through fecal-oral route (this is incorrect because Giardia is indeed transmitted through the fecal-oral route, but it's not the best answer choice).
* **Option B:** Giardia does not have a significant effect on the liver (this is incorrect because Giardia primarily affects the small intestine, but the liver is involved in the metabolism and detoxification of the toxins produced by the parasite).
* **Option C:** Giardia is not a common cause of traveler's diarrhea (this is incorrect because Giardia is a common cause of traveler's diarrhea, particularly in individuals visiting areas with contaminated water).
**Clinical Pearl / High-Yield Fact**
Giardiasis is often asymptomatic in immunocompetent individuals, but it can cause severe malabsorption and weight loss in immunocompromised patients, such as those with HIV/AIDS.
**Correct Answer:** C.