A 40-year-old splenectomised farmer from Assam presents with high fever, dark urine, and haemolytic anaemia three weeks after multiple tick bites. Peripheral smear shows intraerythrocytic ring forms arranged in tetrads resembling a Maltese cross, with no malarial pigment seen. The most likely diagnosis is:
- A Falciparum malaria with high parasitaemia
- B Visceral leishmaniasis with haemophagocytosis
- C Babesiosis caused by Babesia microti ✓
- D Bartonellosis due to Bartonella bacilliformis
Correct answer: C. Babesiosis caused by Babesia microti
Explanation
Tetrads of merozoites forming a Maltese cross inside erythrocytes, absence of malarial pigment, and severe haemolysis in an asplenic host after tick exposure are diagnostic of babesiosis. Falciparum rings may resemble Babesia but never form tetrads and always produce haemozoin pigment. Leishmaniasis shows intracellular amastigotes in macrophages rather than red cells, and Bartonella bacilliformi invades red cells as rod-shaped organisms without tetrad formation.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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