Microbiology · Zoonotic and Vector-Borne Infections (Leptospira, Rickettsia, Scrub Typhus, Bartonella)

Weil's disease (icteric leptospirosis) is characterised by severe hepatorenal involvement. During which phase does severe organ dysfunction predominantly occur?

  • A Immune phase (days 7–14 onwards) due to immune-mediated vascular injury and cytokine storm
  • B Leptospiraemic phase (days 1–7) when organisms are in blood and CSF
  • C Convalescent phase (after day 21) when antibody-antigen complexes deposit in glomeruli
  • D Exclusively during the bacteraemia phase when endotoxin is released
Correct answer: A. Immune phase (days 7–14 onwards) due to immune-mediated vascular injury and cytokine storm

Explanation

Leptospirosis has a biphasic course: the leptospiraemic phase (days 1–7) is characterised by bacteraemia with fever and myalgia; the immune phase begins around day 7–14 as antibodies develop and organisms are cleared from blood, yet paradoxically organ damage (jaundice, renal failure, pulmonary haemorrhage) worsens due to immune complex deposition and cytokine-mediated endothelial injury. Leptospira are not gram-negative and do not have classical LPS endotoxin. Glomerular immune complex nephritis contributes but onset is in the immune phase, not convalescent phase.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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