Transmission of all of the following intestinal parasites takes place by the feco-oral route except:
**Core Concept**
The feco-oral route of transmission involves the ingestion of fecal matter, either directly or through an intermediate host, contaminating food, water, or surfaces. This route is a common mechanism for the spread of various intestinal parasites.
**Why the Correct Answer is Right**
The feco-oral route is primarily responsible for the transmission of intestinal parasites such as Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm), and Enterobius vermicularis (pinworm). However, the transmission of certain parasites like Taenia saginata (beef tapeworm) and Hymenolepis nana (dwarf tapeworm) involves a different mechanism. Taenia saginata is typically acquired by consuming undercooked beef containing cysticerci, while Hymenolepis nana has a direct life cycle involving humans as both the definitive and intermediate host.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as Ascaris lumbricoides, a common roundworm, is transmitted through the feco-oral route.
* **Option C:** This option is incorrect as Enterobius vermicularis, a pinworm, is also transmitted through the feco-oral route.
* **Option D:** This option is incorrect as Trichuris trichiura, a whipworm, is transmitted through the feco-oral route.
**Clinical Pearl / High-Yield Fact**
When considering the transmission of intestinal parasites, remember the "Food-Water-Hand" pathway, where contaminated food, water, or surfaces can facilitate the feco-oral route of transmission.
**Correct Answer:** B.