Plasmodium falciparum malariaThe deadliest species and the cause of nearly all severe malaria. Dominant in sub-Saharan Africa, accounting for ~99% of African cases. Infected red blood cells sequester in the cerebral, renal, and placental microvasculature, producing cerebral malaria, severe anaemia, and acute kidney injury. No dormant liver stage, but parasitaemia can rise tenfold every 48 hours if untreated.
Plasmodium vivax malariaThe most geographically widespread species and the leading cause of malaria outside Africa, dominant in South and Southeast Asia, Latin America, and the Horn of Africa. Forms dormant liver-stage hypnozoites that reactivate weeks to years later as relapses. Severe disease is less common than with P. falciparum but well documented. Duffy-negative individuals in West Africa are mostly resistant.
Plasmodium ovale malariaBiologically similar to P. vivax with relapsing hypnozoites; largely confined to West and Central Africa and parts of Southeast Asia. Two subspecies (P. ovale curtisi and P. ovale wallikeri) are recognised. Often milder than P. vivax, but radical cure with an 8-aminoquinoline is still required to prevent relapse.
Plasmodium malariae malariaCauses a chronic, low-grade quartan fever every 72 hours and can persist asymptomatically in the bloodstream for decades. Distributed worldwide but at low intensity. Long-standing infection occasionally produces immune-complex glomerulonephritis (quartan nephropathy).
Plasmodium knowlesi malariaA simian malaria of long-tailed and pig-tailed macaques that is transmitted to humans in the forested regions of Borneo, Malaysia, Indonesia, and parts of mainland Southeast Asia. The 24-hour erythrocytic cycle means parasitaemia rises faster than any other species, and severe disease develops quickly without recognition.
Uncomplicated malariaSymptomatic infection with detectable parasitaemia in a patient who is alert, able to tolerate oral medication, and free of any WHO severity criterion. Treated with a 3-day artemisinin-based combination therapy (ACT) regimen.
Severe malariaWHO-defined as infection with one or more of impaired consciousness (Glasgow Coma Scale <11), prostration, multiple convulsions, respiratory distress with acidotic breathing, circulatory collapse, abnormal bleeding, jaundice with parasitaemia, severe anaemia (haemoglobin <5 g/dL in children or <7 g/dL in adults), hypoglycaemia, acute kidney injury, pulmonary oedema, or hyperparasitaemia (>10%). Requires parenteral artesunate and intensive care.
