Malaria

A notifiable febrile illness caused by Plasmodium parasites transmitted by Anopheles mosquitoes. Suspect in any febrile returned traveller — malaria must be excluded first (see Illness in returned traveller).

• Species: P. falciparum, P. vivax, P. knowlesi, P. malariae, P. ovale. falciparum and knowlesi are the most pathogenic; falciparum is the most drug-resistant.

Diagnosis

• Malaria antigen test (or NAAT) is now first-line when febrile; send EDTA blood for thick and thin films (thick = detection, thin = speciation/parasite count) to confirm species or after a positive antigen result — films are rarely used as the initial test now, given the shortage of skilled microscopists.
• A single negative test does not exclude malaria — repeat (e.g. ×2–3 over 24–48 h) if the patient remains unwell, especially if antimalarials were taken. Common travel antibiotics (co-trimoxazole, tetracyclines, quinolones) have antimalarial activity and can suppress/mask disease.
• Usually presents within weeks, but can be delayed months (especially vivax/ovale).

Assessment — uncomplicated vs severe

Severe malaria (any one → urgent IV therapy, specialist referral, usually falciparum): parasitaemia >100,000/microL (>2% RBCs), impaired consciousness, jaundice, oliguria/AKI, respiratory distress, severe anaemia, hypoglycaemia, repeated vomiting, or acidosis.

Management

Uncomplicated malaria (oral):

• Artemether–lumefantrine (ACT) is first-line — 6 doses over 60 h with fatty food/full-fat milk (adult >34 kg: 4 tablets at 0, 8, 24, 36, 48, 60 h).
• Atovaquone–proguanil (4 tablets daily ×3 days) is an alternative and preferred in the first trimester.
• Quinine + doxycycline (or clindamycin in pregnancy/children <8) is an alternative 7-day regimen.
• falciparum from the Greater Mekong Subregion with slow response (parasitaemia persisting >72 h) → expert advice (artemisinin resistance). In malaria-receptive northern Australia, add single-dose primaquine (screen for G6PD deficiency — haemolysis risk).
• vivax/ovale — add primaquine (or tafenoquine for vivax) to eradicate dormant liver hypnozoites and prevent relapse (G6PD screen first).
• Monitor parasite count daily until negative; repeat FBC + film at days 7 and 28 to detect recrudescence.

Severe malaria — mandatory IV artesunate (drug of choice, including in pregnancy); add IV quinine for Greater Mekong-acquired disease; adjuncts as indicated (e.g. ceftriaxone for co-existing bacteraemia). Switch to oral once improving.

Prophylaxis

Seek expert advice for children, pregnancy, long stays (>8 weeks), complex itineraries, and high-risk areas. Bite avoidance (repellent, long light-coloured clothing, screened/netted sleeping, avoid dusk-to-dawn outdoors) is essential. Options:

• Atovaquone–proguanil (Malarone) — 1–2 days before until 7 days after.
• Doxycycline 100 mg daily — 1–2 days before until 4 weeks after.
• Mefloquine 250 mg weekly — 2–3 weeks before until 4 weeks after.

Strongly advise pregnant women and people with asplenia/hyposplenism against travel to areas with drug-resistant falciparum. Consider prophylaxis for migrants returning to visit friends/relatives (risk often underappreciated). Travellers declining prophylaxis can carry stand-by treatment (artemether–lumefantrine or atovaquone–proguanil) if care may be >48 h away.