A 8 years old child is preceniting with perianal itching. Perianal scrabbing/swab is showing following bile non-stained eggs. The causative parasite is-
**Core Concept**
The question is testing the student's knowledge of intestinal parasites, specifically those that cause perianal itching in children. The correct answer involves identifying a parasite that lays eggs, which are found in the stool or perianal region.
**Why the Correct Answer is Right**
The parasite that causes perianal itching in children is *Enterobius vermicularis*, also known as the pinworm. The eggs are ingested, usually through fecal-oral transmission, and hatch in the small intestine. The larvae migrate to the large intestine and mature into adult worms, which lay eggs in the perianal region. The eggs are then ingested, perpetuating the cycle. The perianal itching is due to the movement of the worms and the body's allergic reaction to the eggs.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because *Ascaris lumbricoides*, the roundworm, does not typically cause perianal itching in children. Its primary symptoms are abdominal pain, diarrhea, and weight loss.
* **Option B:** This option is incorrect because *Trichuris trichiura*, the whipworm, primarily causes rectal bleeding and weight loss in children, not perianal itching.
* **Option C:** This option is incorrect because *Taenia saginata*, the beef tapeworm, does not cause perianal itching in children. Its primary symptoms are abdominal pain, weight loss, and diarrhea.
**Clinical Pearl / High-Yield Fact**
The key to diagnosing pinworm infection is to look for the characteristic eggs in the perianal region, especially at night when the worms are most active. A simple method to collect the eggs is to place a piece of clear tape over the perianal region in the morning, and then examine it under a microscope.
**Correct Answer: D. Enterobius vermicularis**