Tropical Medicine

Malaria - Mosquito's Deadly Kiss

• Agents: Plasmodium spp. (P. falciparum (Pf), P. vivax (Pv)).
• Cycle: Sporozoite → Merozoite → Gametocyte.
• Features: Paroxysms (chill, fever, sweat). Pf: malignant tertian/quotidian fever. Pv: benign tertian.
  • Complications (Pf): Cerebral malaria (altered sensorium, seizures), blackwater fever (hemoglobinuria), severe anemia, hypoglycemia, ARDS, renal failure.
• Dx: Peripheral smear (Giemsa), RDTs (HRP2, pLDH).
• Rx (Uncomp.):
  • Pf: ACT (e.g., AS+SP).
  • Pv/Po: Chloroquine + Primaquine (0.25 mg/kg/day for 14 days for radical cure).
• Rx (Severe Pf): IV Artesunate 2.4 mg/kg.

⭐ Drug of choice for uncomplicated P. falciparum malaria in India: Artemisinin-based Combination Therapy (ACT, e.g., AS+SP). For P. vivax: Chloroquine + Primaquine for 14 days (radical cure).

Dengue & Chikungunya - Aching Arboviruses

⭐ Chikungunya is notorious for severe, debilitating, and often prolonged polyarthralgia/arthritis, which can persist for months to years.

Leishmaniasis (Kala-azar) - Sandfly's Stealthy Strike

• Visceral Leishmaniasis (VL) / Kala-azar:
  • Agent: L. donovani (India).
  • Vector: Phlebotomus argentipes (Sandfly).
• Clinical Features (Kala-azar Pentad):
  • 1. Prolonged fever (>2 weeks).
  • 2. Massive splenomegaly.
  • 3. Hepatomegaly.
  • 4. Weight loss.
  • 5. Pancytopenia.
  • Plus: Hypergammaglobulinemia (↑IgG).
• Diagnosis:
  • rk39 rapid test.
  • LD bodies (Leishman-Donovan) in bone marrow/splenic aspirate (gold standard).
• Treatment:
  • Amphotericin B (liposomal preferred).
  • Miltefosine (oral).
  • Paromomycin.
• Post-Kala-azar Dermal Leishmaniasis (PKDL): Maculo-papular/nodular rash post-VL treatment.
• Cutaneous Leishmaniasis (CL): Localized skin ulcers (e.g., L. tropica).

⭐ The Aldehyde test (Formalin gel test) is a classical, though less specific, bedside test for Kala-azar due to high globulin levels.

Lymphatic Filariasis & Helminths - Unwanted Guests

• Lymphatic Filariasis (LF)
  • Causative: Wuchereria bancrofti, Brugia malayi, B. timori.
  • Vector: Culex, Anopheles, Aedes, Mansonia mosquitoes.
  • Clinical: Asymptomatic microfilaremia, acute adenolymphangitis (ADL), chronic (lymphedema, elephantiasis, hydrocele).
  • Diagnosis: Night blood smear (microfilariae), DEC provocation test, antigen detection (ICT for W. bancrofti).
  • Treatment: Diethylcarbamazine (DEC) 6 mg/kg/day x 12 days; Ivermectin + Albendazole.
  • Mass Drug Administration (MDA): Annual DEC + Albendazole.

⭐ Nocturnal periodicity of Wuchereria bancrofti microfilariae (peak 10 PM - 2 AM) is crucial for timing blood sample collection.

• Other Key Helminths

High‑Yield Points - ⚡ Biggest Takeaways

• Malaria: P. falciparum causes severe forms; Artemisinin-based Combination Therapy (ACT) is the mainstay treatment.
• Dengue: Monitor for warning signs (e.g., abdominal pain, persistent vomiting, mucosal bleed); judicious fluid therapy is life-saving.
• Kala-azar (VL): L. donovani (sandfly vector); features fever, massive splenomegaly, pancytopenia; rK39 test for diagnosis.
• Lymphatic Filariasis: W. bancrofti most common; causes lymphedema/elephantiasis; DEC for mass drug administration.
• Leprosy: Diagnosed by cardinal signs (hypopigmented anaesthetic patches, thickened nerves, acid-fast bacilli); Multidrug Therapy (MDT) is crucial.
• Typhoid Fever: Characterized by step-ladder fever, rose spots; risk of intestinal perforation and hemorrhage.