Question:medium
Identify the organism related to the blood smear image.
Identify the organism related to the blood smear image.
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Multiple ring-form trophozoites inside red cells with high parasitaemia means P. falciparum.
Updated On: Jun 24, 2026
- P. falciparum
- S. Typhi
- Treponema pallidum
- Toxoplasma gondii
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Localise the parasite. The organisms sit inside red blood cells as delicate signet-ring forms, and one erythrocyte carries several rings at once. Intra-erythrocytic ring trophozoites are the calling card of malaria, and the multiple-ring, high-density picture specifically favours Plasmodium falciparum.
Step 2: Use the density argument. A smear in which a large fraction of red cells are infected, with double or quadruple rings per cell, reflects the intense parasitaemia that falciparum uniquely produces because it infects red cells of all ages.
Step 3: Recall smear roles. The thin film shown here resolves morphology well enough to call the species, complementing the thick film whose job is sensitive detection. The crisp ring forms therefore allow a confident species label of falciparum.
Step 4: Exclude the rest. S. Typhi is an extracellular bacterium not seen as red-cell rings, Treponema pallidum is a thin spiral organism needing dark-field, and Toxoplasma appears as crescentic tachyzoites or cysts in tissue, none matching ring forms within erythrocytes.
\[\boxed{\text{P. falciparum}}\]
Step 2: Use the density argument. A smear in which a large fraction of red cells are infected, with double or quadruple rings per cell, reflects the intense parasitaemia that falciparum uniquely produces because it infects red cells of all ages.
Step 3: Recall smear roles. The thin film shown here resolves morphology well enough to call the species, complementing the thick film whose job is sensitive detection. The crisp ring forms therefore allow a confident species label of falciparum.
Step 4: Exclude the rest. S. Typhi is an extracellular bacterium not seen as red-cell rings, Treponema pallidum is a thin spiral organism needing dark-field, and Toxoplasma appears as crescentic tachyzoites or cysts in tissue, none matching ring forms within erythrocytes.
\[\boxed{\text{P. falciparum}}\]
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