AKT · Infections/Tropical, zoonotic & travel

Malaria

Plasmodium (falciparum most dangerous; vivax/ovale/malariae/knowlesi) — Anopheles mosquito

Overview

A protozoan infection transmitted by the Anopheles mosquito, and the most important diagnosis to consider in any febrile returning traveller. Plasmodium falciparum causes the severe, potentially fatal disease; vivax and ovale form dormant liver hypnozoites that cause relapse. Diagnosis is by thick and thin blood films (×3). Severe falciparum malaria is a medical emergency treated with IV artesunate; uncomplicated falciparum with an oral artemisinin-combination therapy (ACT).

Recognise

Fever (often cyclical), rigors, headache, myalgia, malaise in a traveller returning from an endemic area — symptoms can start months later; anaemia, jaundice, splenomegaly, thrombocytopenia
SEVERE falciparum: impaired consciousness/cerebral malaria, seizures, hypoglycaemia, acidosis, AKI, ARDS, DIC, haemoglobinuria ('blackwater fever'), parasitaemia >2%, shock
Vivax/ovale: dormant liver HYPNOZOITES → relapse (need eradication with primaquine after G6PD testing)

Red flags

Severe/complicated falciparum malaria (cerebral, hypoglycaemia, acidosis, AKI, high parasitaemia) → medical EMERGENCY → IV artesunate + critical care
ALWAYS consider malaria in a febrile returning traveller — a missed diagnosis can be rapidly fatal

Differentials & how to tell them apart

Other febrile-traveller illnessenteric fever (typhoid), dengue, viral hepatitis, leptospirosis, HIV seroconversion — travel/exposure history + films

Sepsis of other sourcebut malaria must be actively excluded with films in any returning traveller

Influenza/viral illnessno travel exposure; films negative

Plasmodium falciparum within red blood cells (blood film)
Ernst Hempelmann / Public domain — Wikimedia Commons

Investigations

THICK and THIN blood films (thick = detect parasites; thin = species + parasitaemia %) — repeat ×3 over 48 h before excluding; rapid antigen tests as adjunct; FBC (anaemia/thrombocytopenia), glucose, U&Es, LFTs, lactate, coagulation; assess severity criteria.

Management

Severe falciparum → IV artesunate; uncomplicated falciparum → oral ACT; vivax/ovale → +primaquine (check G6PD)

1In ANY febrile returning traveller, send thick and thin blood films (repeat ×3 over 48 h before excluding) and assess severity. Determine species and parasitaemia.Gate: Severe/complicated falciparum (cerebral malaria, hypoglycaemia, acidosis, AKI, parasitaemia >2%) is an EMERGENCY → IV artesunate + critical care, not oral therapy.
2Uncomplicated falciparum → oral ACT (artemether-lumefantrine); non-falciparum vivax/ovale → treat then give primaquine to eradicate hypnozoites (check G6PD first). Counsel travellers on ABCD prevention.

Severe/complicated falciparum: IV ARTESUNATE (+ critical care) — first-line for severe malaria (replaced quinine); switch to oral ACT after ≥24 h when improving; treat hypoglycaemia/seizures/AKI

Uncomplicated falciparum: oral ACT (artemether-lumefantrine) — give with food; caution QT/electrolytes

Non-falciparum (vivax/ovale): chloroquine (or ACT) THEN primaquine to eradicate hypnozoites — check G6PD before primaquine (haemolysis risk) — prevents relapse

Prevention (travel): chemoprophylaxis + bite avoidance — ABCD — Awareness, Bite avoidance, Chemoprophylaxis, Diagnosis promptly; agent per region/resistance

Key points

Febrile returning traveller = malaria until excluded → THICK & THIN films ×3. Falciparum is the killer: severe disease (cerebral/hypoglycaemia/acidosis/AKI/parasitaemia >2%) → IV ARTESUNATE emergency; uncomplicated → oral ACT. Vivax/ovale have liver HYPNOZOITES → add primaquine to prevent relapse (check G6PD first). Prevention = ABCD.

Monitor & prognosis

Parasitaemia/films, glucose/lactate/renal function in severe disease, response; G6PD before primaquine.

Uncomplicated malaria treated promptly does well; severe falciparum has significant mortality without rapid IV artesunate.

Source: UK malaria treatment guidelines; cross-ref haematology (G6PD)