Question
A child presents with anal pruritus. Microscopy of the stool sample reveals a plano-convex, kidney-shaped egg. Identify the pathogen.
| A. |
Trichuris |
| B. |
Enterobius |
| C. |
Ascaris |
| D. |
Ancylostoma |
|
Correct Answer » B Explanation |
 |
Enterobius vermicularis* (pinworm) causes anal pruritus, especially at night, due to female worms laying eggs around the perianal area.
– Eggs are plano-convex (flattened on one side) and “kidney-shaped,” which is characteristic of *Enterobius*.
– The eggs are not typically found in stool because the females deposit eggs on the perianal skin, so Scotch tape test is more commonly used; however, stool microscopy may still detect some eggs.
– The patient’s symptom of intense perianal itching, combined with the egg morphology, confirms *Enterobius*.
—Etiology & Pathogenesis:
– Nematode causing enterobiasis, spread via fecal-oral route.
– Females migrate nightly to perianal skin to lay eggs causing intense itching.
– Clinical Features:
– Anal pruritus, worse at night.
– Sometimes irritability, sleep disturbances in children.
– Diagnostic Findings:
– Eggs are plano-convex, asymmetric, flattened on one side (“D” or kidney-shaped).
– Scotch tape test better for detection than stool microscopy.
– Management & Prognosis:
– Treated with mebendazole or albendazole.
– Reinfection common; treat household contacts and hygiene is crucial.
– Excellent prognosis with treatment.