Question

A patient presents with perianal itching. A peripheral swab was taken, and the image below shows the findings. What is the most likely diagnosis?

• A. H Nana
• B. Ancylostoma
• C. Enterobius vermicularis
• D. Necator Americanus

Hint:

In cases of perianal itching, especially at night, consider Enterobius vermicularis. Perform the "tape test" to detect pinworm eggs.

Answer 1

The Correct Option is C

Step 1: Start from the symptom, not the swab.
Perianal itching, classically worse at night (nocturnal pruritus ani), is the keynote. The cause is the parasite whose females migrate out of the anus at night to deposit eggs on the perianal skin.

Step 2: Name that parasite.
That behaviour belongs to the pinworm, $\textit{Enterobius vermicularis}$ (enterobiasis). The diagnostic test fits perfectly: a peri-anal swab / cellophane (NIH Scotch-tape) preparation shows the characteristic eggs - ovoid and flattened on one side (D-shaped). This sampling method is used precisely because the eggs are on perianal skin, not reliably in stool.

Step 3: Discard the others by symptom mismatch.
• $\textit{Hymenolepis nana}$ (dwarf tapeworm) - usually asymptomatic or mild abdominal complaints; eggs found in stool, not on a perianal swab.
• $\textit{Ancylostoma duodenale}$ and $\textit{Necator americanus}$ (hookworms) - cause ground-itch at entry, then iron-deficiency anaemia and abdominal pain; their eggs are passed in faeces and they do not produce nocturnal perianal pruritus.

Step 4: Conclude.
Perianal itching + diagnostic perianal swab = pinworm.

Final Answer: Option 3 - Enterobius vermicularis.