Question

A 15-year-old boy presented with fever and chills for 3 days. On examination he had a delayed skin pinch time and dry oral mucosa. A peripheral blood smear revealed the following picture. Identify the pathogen involved.

• A. Babesia
• B. Plasmodium vivax
• C. Plasmodium falciparum
• D. Salmonella typhi

Hint:

Banana-shaped gametocytes and several delicate rings in one red cell point to one species.

Answer 1

The Correct Option is C

Step 1: Fever with chills plus dehydration (delayed skin pinch, dry mucosa) suggests malaria. The smear is the deciding clue.
Step 2: The smear shows tiny, delicate early rings about one-sixth of the red-cell diameter, binucleate rings (double chromatin) resembling stereo headphones, several rings inside one red cell, rings hugging the cell margin (applique or accole form), and crescent or banana-shaped gametocytes. Every one of these features is typical of Plasmodium falciparum.
Step 3: Note on the key: the recall sheet marked option B, but its own explanation describes P. falciparum, and banana-shaped gametocytes with multiply-infected cells are specific for falciparum, not vivax. In these options P. falciparum is option C, so the medically correct answer is C. P. vivax shows enlarged red cells with Schuffner dots and amoeboid trophozoites; Babesia gives a Maltese-cross tetrad without gametocytes or pigment; Salmonella typhi is not seen on a malaria smear. Ref: Paniker's Textbook of Medical Parasitology, 8e, p.73; Jawetz Medical Microbiology, 27e, p.721.