Malaria — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Malaria is a life-threatening infectious disease caused by Plasmodium parasites transmitted to humans through the bites of infected female Anopheles mosquitoes. Five Plasmodium species infect humans: P. falciparum (most dangerous — causes 99.7% of malaria deaths in Africa; can cause severe and cerebral malaria), P. vivax (second most common globally — can relapse from dormant liver hypnozoites years later), P. ovale (also has dormant liver stage), P. malariae (mild, can persist for decades), and P. knowlesi (zoonotic — Southeast Asia, rapidly progressive). The Anopheles mosquito feeds at night. The WHO reports 247 million malaria cases and 619,000 deaths in 2021 — a disease killing a child every 2 minutes. Over 95% of deaths occur in sub-Saharan Africa, predominantly in children under 5. Malaria is both preventable and treatable.

Transmission: female Anopheles mosquito bites and inoculates Plasmodium sporozoites into the bloodstream. Sporozoites travel to the liver (pre-erythrocytic stage: liver schizogony — P. vivax and P. ovale also form dormant hypnozoites causing relapse). Merozoites released from liver invade red blood cells (RBCs — erythrocytic stage: asexual replication every 48-72 hours causes RBC rupture, releasing merozoites and causing the characteristic fever cycles). Gametocytes formed in RBCs are ingested by mosquitoes, completing the life cycle in the insect (sporogonic cycle). Geographic risk: Sub-Saharan Africa, South and Southeast Asia (India, Pakistan, Bangladesh, Myanmar, Thailand), Central and South America, the Pacific Islands, and the Middle East (Yemen). Highest risk: children under 5 (not yet acquired partial immunity), pregnant women, travellers to endemic areas (no immunity), and immunocompromised individuals. Transmission is also possible through blood transfusion, needle sharing, and from mother to newborn (congenital malaria).

Incubation period: 7-30 days (P. falciparum: 7-14 days; P. vivax/ovale: 12-18 days but can be months to years due to hypnozoite reactivation). Classic malaria paroxysm (every 48 hours for P. vivax/ovale, 72 hours for P. malariae): cold stage (rigors, shivering), hot stage (high fever 39-41°C, headache, myalgia, nausea, vomiting), and sweating stage (profuse sweating, temperature falls, patient feels relatively better). P. falciparum malaria: often atypical and more severe — daily or irregular fever, anaemia (haemolytic), splenomegaly, jaundice, thrombocytopenia. Severe P. falciparum malaria criteria (WHO): cerebral malaria (impaired consciousness — GCS below 11), severe anaemia (Hb below 7 g/dL), respiratory distress (ARDS — pulmonary oedema), metabolic acidosis, hypoglycaemia, hyperparasitaemia (more than 5% parasitaemia), renal failure (blackwater fever — haemoglobinuria causing dark urine and renal failure), circulatory collapse (algid malaria — septic shock), and convulsions. Severe malaria is a medical emergency with 15-30% mortality even with treatment. Any returning traveller with fever within 30 days of travel to an endemic area has malaria until proven otherwise.

Malaria must be diagnosed and treated as a medical emergency — delays in diagnosis increase mortality. Thick and thin blood films (Giemsa-stained peripheral blood smear): gold standard — detects Plasmodium parasites; thin film specifies the Plasmodium species and quantifies parasitaemia percentage; thick film is more sensitive but cannot speciate; requires experienced microscopist. Rapid Diagnostic Tests (RDTs): detect Plasmodium-specific antigens (HRP-2 for P. falciparum; pLDH and aldolase for Plasmodium species); results within 15-20 minutes; high sensitivity and specificity (95%+) for P. falciparum; less reliable for low-density non-falciparum infections. Blood film should confirm all RDT-positive and RDT-negative cases where clinical suspicion is high. Malaria PCR (most sensitive — detects sub-microscopic parasitaemia; speciation; identifies drug resistance genes — used for research, epidemiology, and complex cases). Routine blood tests: FBC (normocytic anaemia, thrombocytopenia, leucopenia), LFTs (elevated bilirubin — haemolytic jaundice), blood glucose (hypoglycaemia in severe falciparum malaria and with quinine treatment), renal function (AKI in severe malaria), and blood cultures (to exclude concurrent bacteraemia — particularly in children in Africa).

Uncomplicated P. falciparum malaria: artemisinin-based combination therapy (ACT) is the WHO-recommended first-line treatment — artemether-lumefantrine (Riamet/Coartem — 6-dose course over 3 days; preferred in most settings), dihydroartemisinin-piperaquine, artesunate-amodiaquine, artesunate-mefloquine, or artesunate-pyronaridine. Artemisinin resistance is emerging in South and Southeast Asia (partial resistance — longer clearance times), threatening ACTs; WHO surveillance is ongoing. Uncomplicated non-falciparum malaria: chloroquine-sensitive P. vivax, P. ovale, P. malariae: chloroquine. P. vivax and P. ovale: require radical cure with primaquine (14-day course) or tafenoquine (single dose) to eliminate liver hypnozoites — test for G6PD deficiency before prescribing (primaquine causes haemolytic anaemia in G6PD-deficient individuals). Severe malaria: IV artesunate (preferred over IV quinine — superior efficacy, better tolerated) for at least 24 hours until the patient can take oral therapy; then complete with oral ACT. IV quinine + IV doxycycline if artesunate unavailable. Supportive care: fluid management (cautious — risk of pulmonary oedema and cerebral oedema), antipyretics (paracetamol), blood transfusion for severe anaemia, renal replacement therapy for AKI, mechanical ventilation for ARDS. Malaria vaccines: RTS,S/AS01E (Mosquirix — WHO-recommended for children in high-transmission sub-Saharan Africa since 2021; 4-dose schedule; 50-75% efficacy against severe malaria); R21/Matrix-M (second vaccine approved by WHO in 2023 — higher efficacy 75-80% in trials).

Severe malaria, caused predominantly by Plasmodium falciparum, is a medical emergency with mortality of 15-20% even with treatment. Complications include: cerebral malaria (parasite sequestration in cerebral microvasculature causing seizures, coma, and death — most common fatal complication); severe anaemia (haemoglobin below 70 g/L from haemolysis and dyserythropoiesis — particularly dangerous in children and pregnant women); acute respiratory distress syndrome (ARDS — non-cardiogenic pulmonary oedema occurring in up to 25% of adults with severe malaria); acute kidney injury (from haemoglobin nephropathy — 'blackwater fever', microangiopathic haemolytic anaemia, and direct endothelial damage — occurring in 10-30% of adults); hypoglycaemia (from impaired hepatic gluconeogenesis and quinine-induced insulin secretion — blood glucose below 2.2 mmol/L); circulatory collapse (algid malaria — septic shock-like syndrome); and disseminated intravascular coagulation (DIC). In pregnancy, malaria causes placental sequestration leading to intrauterine growth restriction, low birth weight, preterm delivery, and maternal death. Hyperparasitaemia (greater than 5% parasitised red blood cells) requires urgent IV artesunate with possible exchange transfusion. Splenomegaly (tropical splenomegaly syndrome) and hypersplenism develop with chronic repeated malaria infections. Neurological sequelae (epilepsy, cognitive impairment, behavioural problems) are documented in up to 10% of cerebral malaria survivors in children.

ABCD of malaria prevention for travellers: Awareness of risk, Bite prevention, Chemoprophylaxis, Diagnosis and prompt treatment. Bite prevention: use DEET-containing insect repellent (50% DEET); sleep under permethrin-treated insecticide-treated bed nets (ITNs); wear long-sleeved clothing and long trousers in the evening; stay in air-conditioned or well-screened accommodation. Chemoprophylaxis (malaria tablets): choice depends on destination resistance patterns; atovaquone-proguanil (Malarone — daily, start 1-2 days before, continue 7 days after; excellent for short trips, well-tolerated), doxycycline (daily, start 1-2 days before, continue 4 weeks after), mefloquine (weekly, start 2-3 weeks before, continue 4 weeks after — side effects include neuropsychiatric effects). Standby emergency treatment (SBET) for remote travellers. Community prevention: indoor residual spraying (IRS) with insecticide; intermittent preventive therapy in pregnancy (IPTp with sulfadoxine-pyrimethamine) and in infants (IPTi). Malaria vaccine (RTS,S/R21) deployed in sub-Saharan Africa for eligible children. Seek travel medicine clinic advice before travel to endemic areas.

Any fever developing within 30 days of return from a malaria-endemic area is a medical emergency until malaria is excluded. Seek emergency assessment at a hospital with access to malaria blood films immediately — do not wait to see if the fever resolves. Malaria can be rapidly fatal, particularly P. falciparum, and deterioration can occur within hours. Call 999 or go to A&E immediately for: fever with confusion or reduced consciousness, breathing difficulty, jaundice, dark urine (haemoglobinuria), seizures, or inability to keep fluids down. Inform the emergency department that you have been in a malaria-endemic area. Travellers should maintain a high index of suspicion for malaria even if they have been taking chemoprophylaxis — no prophylactic regimen is 100% effective.