Malaria
System: Bloodstream and Sepsis · Parent MOC: MOC - Diseases by System · Domain: MOC - Parasitology
One-Sentence Definition
Malaria is a mosquito-borne febrile illness caused by Plasmodium species, diagnosed primarily by blood smear or rapid antigen/PCR tests — P. falciparum is the medical emergency because of severe disease and cerebral malaria.
Clinical Presentation
- Cyclic fever, chills, sweats, headache, myalgia
- Anemia, splenomegaly
- Severe: cerebral malaria, ARDS, renal failure, hypoglycemia, high parasitemia
- Relapsing P. vivax/ovale (hypnozoites)
Pathogens
| Species | Notes |
|---|---|
| P. falciparum | Most severe; cerebral malaria; chloroquine resistance common |
| P. vivax / P. ovale | Relapse; Duffy negativity protects vs vivax in some populations |
| P. malariae | Nephrotic syndrome association (chronic) |
| P. knowlesi | Zoonotic; can be severe |
Pathogenesis
- Sporozoites → liver → merozoites rupture RBCs → cyclic symptoms
- Cytoadherence (falciparum) → microvascular sequestration
Diagnosis
| Step | Test | Note |
|---|---|---|
| First-line | Thick/thin blood smear | Species ID + parasitemia % |
| Rapid | Antigen card (HRP2/pLDH) | Faster; know false-positive HRP2 after treatment |
| Molecular | PCR | Travel/imported cases, low parasitemia |
| Travel | Always ask exposure history | Incubation weeks–months |
Treatment Principles
- Species and resistance map guide therapy (artemisinin combinations for falciparum in most regions)
- P. vivax/ovale: add hypnozoite eradication (e.g., primaquine) after G6PD check
- Severe malaria: IV artesunate — urgent
Prevention
- Chemoprophylaxis for travelers; bed nets; vector control
- No routine human vaccine widely deployed (RTS,S in selected programs)
Differential / Pitfalls
- Typhoid, dengue, viral hepatitis, sepsis — travel history key
- Missing smear in febrile returned traveler = critical error
Related
- MOC - Parasitology · MOC - Public Health & Epidemiology
- Bloodstream and Sepsis · Infection Prevention and Control
Active Recall
- Why is P. falciparum the emergency species?
- Smear vs rapid antigen — what does smear add?
- What causes relapse in vivax/ovale?