Malaria
Summary
Malaria is a life-threatening protozoal disease caused by Plasmodium parasites and transmitted by the bite of an infected female Anopheles mosquito. It is a medical emergency in non-immune travellers. Despite global elimination efforts, it remains a leading cause of death worldwide, particularly in children under 5 in sub-Saharan Africa. The most dangerous species is P. falciparum. [1,2]
Key Facts
- The "Big 5" Species:
- P. falciparum: Malignant. Causes severe disease, cerebral malaria, and death. Prevalent in Africa.
- P. vivax: Benign. Widespread in Asia/South America. Has dormant liver stage (Hypnozoites).
- P. ovale: Benign. West Africa. Has Hypnozoites.
- P. malariae: Mild, chronic. Can persist for decades.
- P. knowlesi: Zoonotic (Macaque monkeys). Southeast Asia. Can be severe (24h replication cycle).
Clinical Pearls
The Golden Rule: Any patient with a fever returning from an endemic area (within 3 months to 1 year) has malaria until proven otherwise. A "negative" rapid test does NOT rule it out (false negatives occur with low parasitaemia). 3 negative films over 3 days are needed to exclude it.
Severe Malaria criteria: Parasitaemia >2% (in non-immune), Altered consciousness, Acidosis (pH less than 7.3), Hypoglycaemia (less than 2.2), Severe Anaemia, or Renal Impairment.
Primaquine Trap: Vivax and Ovale hide in the liver (hypnozoites). You must use Primaquine to eradicate them prevents relapse. BUT, Primaquine causes severe haemolysis in G6PD Deficiency. You MUST check G6PD status before prescribing it.
Transmission
- Vector: Anopheles mosquito. Bites mainly at night (dusk to dawn).
- Incubation:
- Falciparum: 7-14 days. (95% present within 1 month).
- Vivax/Ovale: 12-18 days (but can be months/years).
Geography
- Africa: >90% of global cases. Predominantly Falciparum.
- Asia/Americas: Mixed Falciparum and Vivax.
Lifecycle
- Liver Phase (Exo-erythrocytic): Sporozoites injected by mosquito -> Liver -> Merozoites. (Vivax/Ovale can stay here as dormant hypnozoites).
- Blood Phase (Erythrocytic): Merozoites infect RBCs -> Multiply -> Rupture RBCs -> Fever spike.
- Sequestration: P. falciparum makes RBCs "sticky" (knobs). They adhere to capillary walls (brain, kidneys, lungs) to avoid the spleen. This blockage causes the severe organ damage.
Symptoms
Signs
- Neurology: Assess GCS (Cerebral malaria). Neck stiffness (Meningism).
- Abdomen: Hepatomegaly / Splenomegaly.
- Urine: Dark urine ("Blackwater fever" - Haemoglobinuria).
Microbiology
- Thick and Thin Blood Films (Gold Standard):
- Thick: Sensitive screening (Is the parasite present?).
- Thin: Speciation (Which one?) and Parasitaemia (How many?).
- RDT (Rapid Diagnostic Test):
- Detects antigens (HRP-2 for Falciparum, pLDH for others).
- Good for Falciparum, less sensitive for others.
Supporting Bloods
- FBC: Thrombocytopenia (Low platelets) is very common. Anaemia.
- U&E: Renal failure (AKI).
- LFTs: Unconjugated hyperbilirubinaemia.
- Glucose: Hypoglycaemia (Parasite consumes glucose).
- Blood Gas: Lactate/Acidosis (Markers of severity).
Management Algorithm
CONFIRMED MALARIA
↓
IDENTIFY SPECIES
AND SEVERITY %
↓
┌─────────────┼─────────────┐
UNCOMPLICATED SEVERE NON-FALCIPARUM
FALCIPARUM FALCIPARUM (Vivax/Ovale)
↓ ↓ ↓
ORAL ARTEMISININ IV ARTESUNATE CHLOROQUINE
(Riamet / (Critical Care) (Oral)
Malarone) (Switch to oral ↓
when can eat) CHECK G6PD
↓
ADD PRIMAQUINE
(Radical Cure)
1. Severe Falciparum
- IV Artesunate: Superior to Quinine. Reduces mortality.
- Management: Critical Care. Fluid resuscitation (careful of pulmonary oedema). Glucose support.
- Exchange Transfusion: Considered if parasitaemia >10% (experimental).
2. Uncomplicated Falciparum
- Artemisinin Combination Therapy (ACT):
- Riamet (Artemether-Lumefantrine): 3 day course.
- Malarone (Atovaquone-Proguanil).
- Quinine + Doxycycline: (Second line, poorly tolerated "Cinchonism" side effects).
3. Non-Falciparum (Vivax/Ovale)
- Acute: Chloroquine (Resistance is rare except Indonesia).
- Eradication: Primaquine for 14 days (Hypnozoites).
- Cerebral Malaria: Seizures, Coma. 20% mortality even with treatment.
- Acute Renal Failure: Acute Tubular Necrosis.
- ARDS: Pulmonary oedema (often iatrogenic fluid overload).
- Hypoglycaemia: Caused by the parasite and by Quinine (stimulates insulin).
- Splenic Rupture: Rare, caution with palpation.
- Uncomplicated: Excellent prognosis with prompt treatment.
- Severe: 10-20% mortality.
- Immunity: Partial immunity develops in endemic areas, but is lost rapidly upon leaving (hence emigrants returning home to visit family aka "VFRs" are high risk).
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Malaria Guidelines | UK (ACMP) / WHO | Use IV Artesunate for severe malaria (replaces Quinine). |
| Travel Health | NaTHNaC | Chemoprophylaxis regimens (Doxy/Malarone/Lariam). |
Landmark Trials
1. AQUAMAT and SEAQUAMAT Trials
- Demonstrated that IV Artesunate significantly reduces mortality compared to IV Quinine in both African children and Asian adults with severe malaria. Quinine is now second line.
What is Malaria?
It is a tropical disease spread by mosquitoes. A tiny parasite enters your blood, travels to your liver, multiplies, and then bursts out to attack your red blood cells.
Is it contagious?
No, you cannot catch it from another person (unless via blood transfusion). It only comes from mosquito bites.
Is it curable?
Yes, if caught early. Modern malaria tablets (ACTs) work very fast. However, if left untreated, the "Falciparum" type can block blood vessels to the brain and kidneys, which can be fatal within 24 hours.
Why do I need to take tablets for 2 weeks after I'm better?
(For Vivax/Ovale): Some types of malaria can "sleep" in your liver for months or years and wake up later to make you sick again. The second medicine (Primaquine) is a "liver cleaner" to stop this happening.
Primary Sources
- Lalloo DG, et al. UK malaria treatment guidelines 2016. J Infect. 2016.
- WHO. Guidelines for the treatment of malaria. 3rd edition. 2015.
- Dondorp AM, et al. Artesunate versus quinine for treatment of severe falciparum malaria in African children (AQUAMAT). Lancet. 2010.
Common Exam Questions
- Diagnosis: "Gold standard test?"
- Answer: Thick and Thin blood films.
- Management: "Drug for Severe Malaria?"
- Answer: IV Artesunate.
- Pharmacology: "Side effect of Quinine?"
- Answer: Cinchonism (Tinnitus, Deafness, Headache) + Hypoglycaemia.
- Species: "Which one relapses?"
- Answer: Vivax / Ovale.
- Safety: "Test before Primaquine?"
- Answer: G6PD status.
Viva Points
- Blackwater Fever: Dark urine due to massive intravascular haemolysis and haemoglobinuria.
- Relative Bradycardia: Malaria (and Typhoid) often present with a pulse that is slower than expected for the degree of fever (Faget's sign).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.