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Tropical Medicine Triggers: MSRA High-Yield Guide

🦟 1. Malaria – Core Points


✅ Causative Agents: Plasmodium falciparum (most severe), P. vivax, P. ovale, P. malariae, P. knowlesi (SE Asia)

✅ Life cycle (simplified):

  • Mosquito bite → Sporozoites enter liver → mature into merozoites → enter RBCs → cause symptoms.

  • Vivax/ovale: Have hypnozoites (dormant liver forms) causing relapses months to years later.

  • Falciparum: No dormant stages; symptoms usually within weeks – max 6 months after exposure.

✅ Key symptoms:

  • Fever (>39°C), chills, sweats

  • Headache, malaise, GI upset

  • Severe: Cerebral malaria, hypoglycemia, renal failure, ARDS, blackwater fever (hemoglobinuria) are primarily caused by Plasmodium falciparum due to its ability to:

    • Infect RBCs of all ages → higher parasitemia

    • Cause sequestration (RBC adhesion to endothelium) → microvascular obstruction

✅ Cerebral malaria simplified:

  • What? Falciparum malaria affecting the brain → coma, confusion, seizures

  • Why? Infected RBCs block brain vessels → swelling

  • Treatment: IV artesunate, check blood sugar, control seizures

  • Danger: High mortality and long-term brain problems

⚠️ Vivax and ovale malaria:

  • Generally do not cause severe complications like cerebral malaria.

  • They can occasionally cause severe anaemia or splenic rupture but not cerebral malaria or blackwater fever, which are classic falciparum features.


✅ Treatment summary:

  • Uncomplicated falciparum: Artemisinin-based combination therapy (ACT e.g. artemether-lumefantrine)

  • Severe malaria: IV artesunate (preferred) or IV quinine

  • Vivax/ovale: Chloroquine + primaquine (check G6PD before primaquine)



🏥 2. Dengue Fever – Core Points


✅ Causative agent: Dengue virus (RNA virus) transmitted by Aedes mosquitoes.

✅ Key symptoms:

  • Abrupt fever, severe headache

  • Retro-orbital pain (behind eyes) – exam clincher

  • Muscle and joint pain ("breakbone fever")

  • Severe dengue: hemorrhage, shock, organ failure

✅ Treatment:

  • Supportive care only, monitor for bleeding/shock



🪲 3. Chagas Disease – Core Points

✅ Causative agent: Trypanosoma cruzi (protozoa), transmitted by Triatomine (kissing) bugs.

✅ Key signs:

  • Romaña’s sign: Unilateral periorbital swelling

  • Chronic: Cardiomyopathy, arrhythmias, heart failure

✅ Treatment:

  • Benznidazole or nifurtimox (effective in early disease)



🕷️ 4. Lyme Disease – Core Points

✅ Causative agent: Borrelia burgdorferi (spirochete), transmitted by Ixodes ticks.

✅ Key sign:

  • Erythema migrans rash: Expanding, >5cm, target-like, usually not painful or itchy

✅ Treatment:

  • Doxycycline (first-line), or amoxicillin in pregnancy



🌍 5. Travel Vaccines & Malaria Prophylaxis – UK Travellers


✅ Common vaccines needed:

  • Hepatitis A, Typhoid, Yellow Fever, Cholera, Japanese Encephalitis, Meningococcal (MenACWY), Rabies (depending on destination)

✅ Malaria prophylaxis options:

  • Atovaquone-Proguanil (Malarone): Start 1 day before, continue during travel + 1 week after

  • Doxycycline: Start 1 day before, continue during travel + 4 weeks after

  • Mefloquine: Start 2–3 weeks before, weekly during travel + 4 weeks after

✅ Always combine with bite prevention measures (nets, DEET, clothing).



🎯 Key MSRA Takeaways:

✔️ Malaria: Severe falciparum → cerebral malaria, treat with IV artesunate

✔️ Dengue: Retro-orbital pain + fever → supportive care

✔️ Chagas: Romaña’s sign + chronic cardiac disease

✔️ Lyme: Erythema migrans rash → doxycycline

✔️ Travel: Check vaccines + malaria prophylaxis before departure


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