Tropical Medicine

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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.

Plasmodium falciparum life cycle

⭐ 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

FeatureDengue (DENV 1-4)Chikungunya (CHIKV)
VectorAedes aegypti, A. albopictusAedes aegypti, A. albopictus
Incubation4-10 days3-7 days
FeverHigh, biphasic (saddleback)High, continuous
RashMaculopapular, 'islands of white in sea of red'Maculopapular
ArthralgiaMyalgia prominentSevere, debilitating, often prolonged polyarthralgia
HemorrhagicCommon (petechiae, DHF/DSS)Rare
Warning SignsYes (see below)No specific set
Tourniquet TestOften positiveVariable
DiagnosisNS1 Ag (early), IgM/IgG ELISART-PCR (early), IgM/IgG ELISA
ManagementSymptomatic, crucial fluid managementSymptomatic, NSAIDs for pain

⭐ 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).
      1. Massive splenomegaly.
      1. Hepatomegaly.
      1. Weight loss.
      1. 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). Leishman-Donovan bodies in macrophage

⭐ 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.

Wuchereria bancrofti microfilaria in blood smear

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

  • Other Key Helminths
HelminthOrganismTransmissionKey Feature/ComplicationDxDOC
AscariasisA. lumbricoidesFeco-oralIntestinal obstructionStool (ova)Albendazole
HookwormAncylostoma, NecatorSkin penetrationIron deficiency anemiaStool (ova)Albendazole
StrongyloidiasisS. stercoralisSkin penetrationHyperinfection syndromeLarvae (stool/sputum)Ivermectin
TaeniasisT. solium/saginataIngest larvaeCysticercosis (T.s)Stool (ova/proglottids)Praziquantel

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.

Practice Questions: Tropical Medicine

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All of the following helps in the diagnosis of leishmaniasis except:

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Flashcards: Tropical Medicine

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_____ is a helminth that can result in megaloblastic anemia due to B12 (cobalamin) deficiency

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_____ is a helminth that can result in megaloblastic anemia due to B12 (cobalamin) deficiency

Diphyllobothrium latum

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