Leishmaniasis

Leishmaniasis Basics - Sandfly's Sting

• Protozoan disease by Leishmania spp.; transmitted by female Phlebotomus sandfly bite.
• Key Indian Species:
  • L. donovani (Visceral Leishmaniasis/Kala-azar)
  • L. tropica (Cutaneous Leishmaniasis)
• Vector: Phlebotomus argentipes (main vector for VL in India).
• Life Cycle:
  • Sandfly: Ingests amastigotes → develop to promastigotes (infective).
  • Human: Promastigotes injected → transform to amastigotes in macrophages (diagnostic).
• Endemic (India): Bihar, Jharkhand, West Bengal, E. Uttar Pradesh.

⭐ Diagnostic stage: Amastigotes (Leishman-Donovan bodies) within human macrophages.

Disease Spectrum - Skin & Spleen Saga

• Visceral Leishmaniasis (Kala-azar / Black Fever)

  • Agent: L. donovani (India).
  • Incubation: 2-6 months (variable).
  • Classic Triad:
    • Prolonged fever (>2 weeks).
    • Massive splenomegaly (± hepatomegaly).
    • Progressive weight loss, cachexia.
  • Lab: Pancytopenia (↓Hb, ↓WBC, ↓Platelets), polyclonal hypergammaglobulinemia (↑IgG).
  • Post-Kala-azar Dermal Leishmaniasis (PKDL):
    • Hypopigmented macules, papules, nodules, plaques.
    • Appears 6 months - 2 years (or more) post-VL treatment.
    • Important reservoir of infection.

• Cutaneous Leishmaniasis (CL)

  • Agents: L. tropica, L. major.
  • Forms:
    • Localized (LCL): "Oriental Sore", "Delhi Boil". Most common.
    • Diffuse (DCL): Anergic, widespread nodules.
    • Recidivans (LR): Chronic, relapsing at scar edge.
  • Lesion: Starts as papule → nodule → painless ulcer with raised, indurated "volcano-like" border; may be dry or crusted.
  • Sites: Exposed areas (face, limbs).
  • 

• Mucocutaneous Leishmaniasis (MCL)

  • Rare in India (primarily New World: L. braziliensis).
  • If occurs with L. donovani, involves destructive lesions of nasal, oral, pharyngeal mucosa.

⭐ > Amastigotes (Leishman-Donovan bodies) are found within macrophages in tissue samples (spleen, bone marrow, skin).

Spotting the Parasite - Detective Work

• Visceral Leishmaniasis (VL):
  • Definitive Dx: LD bodies (Giemsa stain) in aspirates (spleen - highest yield, bone marrow, lymph node).
  • Serology: rK39 strip test (rapid), DAT, ELISA.
  • Molecular: PCR (high sensitivity, species ID).
• Cutaneous/Mucocutaneous (CL/MCL):
  • Microscopy: LD bodies in slit-skin smear/tissue imprint (Giemsa).
  • Biopsy for:
    • Histopathology (LD bodies).
    • Culture (NNN medium).
  • Molecular: PCR (species ID).
  • Montenegro Skin Test (Leishmanin):
    • Measures CMI; induration ≥5mm = positive.
    • Positive: Most CL (not DCL), cured VL. Negative: Active VL, DCL.

⭐ The rK39 antigen-based immunochromatographic test is a highly sensitive and specific rapid diagnostic for Visceral Leishmaniasis, crucial in resource-limited settings.

Fighting Back - Drugs & Defense

Treatment:

• Visceral Leishmaniasis (VL / Kala-azar):
  • First-line: Liposomal Amphotericin B (LAmB) (e.g., 10 mg/kg single IV dose - India); Miltefosine (2.5 mg/kg/day PO, 28 days, ⚠️ Teratogenic); Paromomycin IM.
  • Combination therapy (LAmB + Miltefosine or LAmB + Paromomycin) for ↑efficacy, ↓resistance, esp. in endemic areas.
  • Sodium Stibogluconate (SSG): Marked resistance in Indian subcontinent.
• Cutaneous Leishmaniasis (CL):
  • Local: Paromomycin ointment, intralesional SSG, cryotherapy, heat therapy.
  • Systemic (severe/unresponsive): Miltefosine, SSG (if sensitive), azoles (e.g., Ketoconazole).
• Post-Kala-azar Dermal Leishmaniasis (PKDL):
  • Miltefosine or LAmB (often prolonged course, e.g., 12 weeks for Miltefosine).

⭐ Miltefosine: First effective and exclusively oral drug for visceral leishmaniasis.

Prevention & Control:

• Vector (Sandfly) Control: Indoor Residual Spraying (IRS) (e.g., DDT, synthetic pyrethroids), environmental hygiene.
• Personal Protection: Insecticide-treated nets (ITNs), repellents (e.g., DEET).
• Early case detection & complete treatment.
• Health education on disease transmission & personal protection measures.

High‑Yield Points - ⚡ Biggest Takeaways

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