A traveller from South America presents with unilateral periorbital oedema (Romaña's sign), fever, and hepatosplenomegaly. Trypomastigotes with a large kinetoplast are seen on blood smear in a C/U shape. Laboratory tests to confirm the diagnosis include:
- A Thick blood film examination for trypomastigotes during febrile episodes
- B Lymph node aspirate showing trypomastigotes with a small kinetoplast
- C Xenodiagnosis, culture in NNN medium, and PCR for Trypanosoma cruzi ✓
- D IFAT for Leishmania donovani antibodies
Explanation
The scenario describes acute Chagas disease (American trypanosomiasis) caused by Trypanosoma cruzi. Romaña's sign (unilateral painless periorbital oedema from conjunctival portal of entry) is pathognomonic of the acute phase. T. cruzi trypomastigotes are C-shaped or U-shaped on blood smear with a large kinetoplast. Diagnosis in acute phase includes direct blood smear, buffy coat examination, hemoculture in NNN (Novy-McNeal-Nicolle) medium, xenodiagnosis (allowing uninfected triatomine bugs to feed on patient's blood and examining their gut), and serology/PCR. T. brucei (African sleeping sickness) trypomastigotes have a small kinetoplast; Leishmania is diagnosed by tissue aspirates showing amastigotes.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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