Stool sample from a patient shows the following. How do humans get this infection?
**Core Concept**
The patient's stool sample is likely contaminated with *Entamoeba histolytica*, a protozoan parasite that causes amoebiasis. This infection occurs when humans ingest cysts of the parasite, which are usually acquired through fecal-oral transmission.
**Why the Correct Answer is Right**
Entamoeba histolytica cysts are highly resistant to environmental stressors and can survive outside the human body for extended periods. When ingested, the cysts release trophozoites that colonize the large intestine, leading to symptoms such as diarrhea, abdominal pain, and weight loss. The parasite can also invade the intestinal wall and cause liver abscesses in some cases. The primary mode of transmission is through fecal-oral contact, often via contaminated food, water, or hands.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because *Giardia lamblia* is another protozoan parasite that causes gastrointestinal infection, but it is not the primary cause of amoebiasis.
**Option B:** This option is incorrect because *Ascaris lumbricoides* is a nematode worm that causes intestinal infection, but it is not related to amoebiasis.
**Option C:** This option is incorrect because *Cryptosporidium parvum* is another protozoan parasite that causes gastrointestinal infection, but it is not the primary cause of amoebiasis.
**Clinical Pearl / High-Yield Fact**
To prevent amoebiasis, it is essential to maintain good hygiene practices, including proper handwashing, safe food and water handling, and proper disposal of feces. This can help prevent fecal-oral transmission and reduce the risk of infection.
**Correct Answer:** C. Contaminated food, water, or hands.