Malaria

Meet the patient

A 40-year-old woman returns from a two-week trip to a forested belt of Odisha with fever, rigors, and headache, ten days after she stopped her doxycycline prophylaxis early. She is pale, her spleen tip is palpable, and her temperature is 39.5 deg C.[1][4]

This is malaria until a blood film proves otherwise, and the single most important fork is falciparum versus everything else. Send a thick film (for detection) and a thin film (for species and parasitaemia) within 12 hours, and do not wait for the next fever spike — one smear is never enough to exclude it.[1][2]

Overview & Definition

Malaria is an acute and sometimes chronic protozoan illness caused by haemosporidian parasites of the genus Plasmodium and transmitted to humans by the bite of an infected female Anopheles mosquito. Five species cause human disease — P. falciparum, P. vivax, P. ovale, P. malariae and the simian zoonosis P. knowlesi — and the clinical pattern, periodicity, severity and treatment strategy differ across them.[1]

The clinical art in malaria lies in three skills: (1) recognising malaria in a febrile patient (and not missing the diagnosis in a traveller, a pregnant woman or a partially immune adult), (2) distinguishing P. falciparum (potentially fatal) from the benign species and grading severity, and (3) choosing the right ACT for uncomplicated disease and giving intravenous artesunate within minutes for severe disease. A single missed dose of artesunate in cerebral malaria multiplies mortality.[2][4]

Classification

By causative species (the classification that drives treatment, prognosis and public-health response):[1]

• Plasmodium falciparum — commonest cause of severe malaria worldwide; malignant tertian; high parasitaemia, cytoadherence, sequestration; no hypnozoite (no relapse); gametocytocidal drug useful for transmission blocking.
• Plasmodium vivax — commonest cause of malaria outside Africa; benign tertian; forms hypnozoites (dormant liver forms that relapse weeks to years later); preferentially invades reticulocytes (so parasitaemia is low); splenic rupture a recognised complication.
• Plasmodium ovale — relapsing tertian, hypnozoite, milder than vivax, mostly West Africa; rare.
• Plasmodium malariae — quartan (72-hour cycle); chronic low-grade infection persisting for decades; classical association with immune-complex membranous nephropathy (quartan malarial nephrotic syndrome).
• Plasmodium knowlesi — simian parasite of macaques in Southeast Asia (Malaysia, Philippines); quotidian (24-hour) cycle; rapidly rising parasitaemia; mimics falciparum in severity; no hypnozoite. [1]

By severity (any one defining feature mandates parenteral artesunate and ICU-level care):[2][15]

• Cerebral malaria — unrousable coma (Blantyre coma score 2 or less in children) not attributable to another cause.[15][16]
• Impaired consciousness (any degree), respiratory distress, jaundice, hypoglycaemia and renal failure — each independently associated with death in African children (odds ratios 4.4, 2.4, 1.9, 1.7 and 11.1 respectively).[15]
• Severe malarial anaemia — Hb under 5 g/dL in African children.[17]
• Acidosis — hyperlactataemia; blood lactate over 5 mmol/L is among the strongest predictors of death.[15]
• Hypoglycaemia — blood glucose under 2.2 mmol/L, a defining feature of severe malaria.[14]
• Acute kidney injury — an independent predictor of mortality in adults and children.[4][19]
• ARDS / pulmonary oedema and liver dysfunction — mortality-associated severity features in Indian adults.[58]
• Shock ("algid malaria") — a severe-sepsis-like picture, especially in non-immune adults.[54]
• Hyperparasitaemia — over 10 per cent parasitised erythrocytes with organ complications is the classical escalation threshold.[44]
• Haemoglobinuria (blackwater fever) — dark urine with intravascular haemolysis.[12]
• Coagulopathy — coagulation and inflammation link to sequestration in cerebral malaria.[9]

By epidemiological setting:

• Indigenous / acquired locally vs imported (returning traveller).
• Relapse (hypnozoite reactivation, vivax/ovale) vs recrudescence (incomplete blood-stage clearance, falciparum) vs reinfection (new inoculation) — these three are not the same and the distinction matters for treatment and prognosis. [1]

Epidemiology & Risk Factors

Malaria remains one of the most serious infectious diseases worldwide — an estimated 247 million cases and 619,000 deaths in 2021, most of them in the WHO African region, and children under five are especially vulnerable.[1][40]

India accounts for nearly half of the global P. vivax burden; in endemic-state surveys, belonging to a tribal population and lack of formal education are the strongest risk factors for malaria.[43][42]

[40] [1] [2] [22] [18]

Risk factors for acquisition: [1]

• Geography — travel to or residence in the tropics/subtropics (sub-Saharan Africa, South and Southeast Asia, South Pacific, Amazon basin). The higher the transmission intensity in the source country, the higher the risk to a returning traveller.
• Lack of chemoprophylaxis in travellers — single biggest preventable risk.
• Lack of insecticide-treated bed nets — insecticide-treated nets plus insecticide spraying are the backbone of vector control.
• Pregnancy — reduced cellular immunity, sequestration in placenta, higher parasitaemia.
• Age — non-immune children under five in endemic areas; non-immune travellers of any age.
• Asplenia / hyposplenism (surgical, sickle-cell autosplenectomy, coeliac) — risk of overwhelming falciparum and malariae infection.
• HIV/AIDS — higher parasitaemia, worse outcomes in pregnancy.
• Blood transfusion, needle-sharing, vertical (congenital) transmission — bypass the hepatic stage, so incubation is shorter and there are no hypnozoites (no relapse). [1]

Risk factors for severe disease (in a smear-positive patient): non-immune (traveller, child under 5 in low-transmission area), pregnancy, splenectomy/asplenia, HIV, delayed treatment, infection with P. falciparum or P. knowlesi, mixed infections, and intense transmission superimposed on poor access to care.[4]

Pathophysiology

Malaria has two hosts — the female Anopheles mosquito (definitive host — sexual sporogony) and the human (intermediate host — asexual schizogony). A full grasp of the life cycle unlocks every exam question on pathogenesis, relapse, treatment targets and prevention.[1]

The life cycle, step by step: [1]

1. Inoculation. During a blood meal, the infected Anopheles female injects sporozoites from her salivary glands into the human dermis.
2. Hepatic (pre-erythrocytic / exoerythrocytic) schizogony (7 to 30 days; asymptomatic). Sporozoites drain to the liver and invade hepatocytes. Over one to two weeks each sporozoite generates a liver schizont containing 10,000 to 30,000 merozoites. The hepatocyte ruptures, releasing merozoites into the bloodstream.
   • P. vivax and P. ovale ONLY form hypnozoites — dormant parasites in hepatocytes that wake weeks to years later, causing relapse. Radical cure requires primaquine or tafenoquine (no blood schizonticide reaches hypnozoites).
3. Erythrocytic schizogony (the symptomatic blood stage). Merozoites invade red cells via parasite ligand–erythrocyte receptor pairs (e.g. P. falciparum erythrocyte membrane protein / EBA-175 to glycophorin A; P. vivax Duffy-binding protein to the Duffy antigen / Fy). Inside the RBC the parasite passes through ring → trophozoite → schizont stages over 48 hours (tertian; malariae 72 h; knowlesi 24 h). The schizont ruptures, releasing 8 to 24 fresh merozoites, each re-invading a new RBC — and synchronously releasing haemozoin ("malaria pigment") and parasite toxins that trigger the TNF-alpha / IL-1 / IFN-gamma cytokine cascade producing the fever paroxysm.[1]
4. Gametocytogenesis. A fraction of merozoites differentiate into sexual gametocytes (falciparum takes around 10 days; crescent/banana-shaped; infectious to the mosquito). Drugs that target gametocytes (primaquine) reduce transmission — the basis of population-level malaria control.
5. Mosquito stage (sporogony). The mosquito ingests gametocytes during a blood meal; fertilisation in the midgut produces an ookinete → oocyst → sporozoites that migrate to the salivary glands, completing the cycle.

Why is P. falciparum the killer? Cytoadherence, sequestration, rosetting. [1]

• Parasitised RBCs (PRBCs) display P. falciparum erythrocyte membrane protein 1 (PfEMP-1) on their surface (encoded by the var gene family, ~60 copies, antigenic variation). PfEMP-1 binds endothelial receptors — ICAM-1, E-selectin, VCAM-1, CD36, chondroitin sulphate A (placenta), thrombospondin — sequestering PRBCs in the cerebral, renal, pulmonary, intestinal and placental microvasculature, away from splenic clearance.
• Rosetting — PRBCs bind uninfected RBCs, forming aggregates that further obstruct flow.
• Cytokine storm (TNF-alpha, IFN-gamma, IL-1) disrupts the blood–brain barrier, causing cerebral oedema, petechial haemorrhage and coma; loss of endothelial protein C receptor links coagulation and inflammation to sequestration.[9]
• End-organ consequences: cerebral malaria (coma, seizures), severe anaemia (haemolysis + dyserythropoiesis + hypersplenism), ARDS (pulmonary capillary leakage), AKI (acute tubular necrosis from sequestration + haemolysis), hypoglycaemia (parasite consumption of glucose + quinine-driven hyperinsulinaemia), lactic acidosis, and disseminated intravascular coagulation.[4][5]

Cerebral malaria — the prototypical severe phenotype. It should be considered in anybody with impaired consciousness who has recently travelled in a malaria-endemic area; the clinical presentation differs between African children and non-immune adults, and subsequent neurological impairment is commonest and most severe in children.[5][6] In adult cohorts from South-Western India, mortality is significantly higher with cerebral malaria, pulmonary oedema/ARDS, liver dysfunction, severe anaemia, renal failure and metabolic acidosis.[58]

Blackwater fever — massive intravascular haemolysis with haemoglobinuria (dark-red/black urine), classically seen with intermittent quinine use in semi-immune patients (the modern antimalarials have reduced its incidence, but it still occurs). Mechanism: immune-mediated haemolysis, often with quinine-dependent antibodies.[12]

Pathophysiology in one sentence: falciparum kills by microvascular obstruction (cytoadherence + rosetting + sequestration) producing tissue hypoxia, with cytokine-driven systemic inflammation and massive haemolysis as the mediators of coma, anaemia, AKI, ARDS, hypoglycaemia and acidosis. [1]

Clinical Presentation

The classical malaria paroxysm (best seen in primary non-immune vivax infection; often blurred in semi-immune adults and in falciparum) lasts 6 to 10 hours and has three stages:[1]

1. Cold stage (15 to 60 min) — intense chills, rigors, shivering; the patient is pale, cyanotic, and feels cold despite a rising core temperature.
2. Hot stage (2 to 6 h) — fever (39 to 41 °C), headache, nausea, vomiting, myalgia, cough; skin hot and dry.
3. Sweating stage (2 to 4 h) — profuse sweating, fever defervesces, the patient is exhausted and often sleeps. [1]

Periodicity by species (when synchronised — often irregular early in illness): [1]

Uncomplicated malaria — symptoms and signs. Fever (often continuous at first), headache, malaise, myalgia, arthralgia, nausea, vomiting, diarrhoea (mimics gastroenteritis), dry cough and abdominal pain. Examination: splenomegaly (develops after several days; a soft, tender spleen), mild hepatomegaly, mild jaundice, pallor, mild tachypnoea. Children may have only fever and refusal of feeds. [1]

Atypical presentations to expect on an exam: [1]

• Traveller returning from an endemic area — incubation usually 7 to 30 days after the last exposure, but can be months (rarely years) for vivax/ovale (hypnozoite) or malariae; up to 1 year even with chemoprophylaxis. Always include malaria in any febrile traveller for a year after return.
• Pregnant woman — higher parasitaemia, hypoglycaemia, pulmonary oedema, severe anaemia, miscarriage, stillbirth, low-birth-weight baby (the single biggest contributor to malaria-attributable infant mortality); the placenta sequesters PRBCs (cytoadherence to chondroitin sulphate A) so peripheral parasitaemia underestimates the true burden.
• Children — may present with seizures, prostration, deep breathing (acidotic Kussmaul), impaired consciousness without the classical paroxysm; severe anaemia may be the only sign.
• Elderly / comorbid — atypical blunted presentation, rapid progression to multi-organ failure, higher mortality; quinine is poorly tolerated.
• Asplenic / splenectomised patient — overwhelming, rapidly fatal falciparum or malariae infection; can present in septic shock within hours.
• Partially immune adult in an endemic area — may have low-grade fever and parasitaemia that mimics viral illness; asymptomatic parasitaemia is common and the fever may be due to a concomitant bacterial or viral illness — always look for another cause, do not assume the smear is the answer. [1]

Severe falciparum malaria — clinical features by organ (any one mandates IV artesunate and ICU):[4]

• Cerebral — impaired consciousness, seizures (especially children), and malarial retinopathy on fundoscopy, which has diagnostic value in cerebral malaria.[5][66]
• Respiratory — tachypnoea, deep (Kussmaul) breathing (acidosis), chest crackles, ARDS (worsening hypoxia with bilateral infiltrates; risk highest around day 2 to 3, often after the patient is improving).
• Renal — oliguria / anuria, dark urine (blackwater), oedema.
• Metabolic — hypoglycaemia (sweating, tremor, confusion, coma — overlaps with cerebral malaria; check glucose in any unconscious malaria patient), severe acidosis (Kussmaul breathing, low bicarbonate, high lactate).
• Haematological — severe pallor, jaundice, spontaneous bleeding (DIC), petechiae.
• Cardiovascular — shock / "algid malaria" (cold peripheries, weak pulse, hypotension; frequently with concomitant Gram-negative septicaemia). [1]

Differential Diagnosis

In a febrile patient from an endemic area, malaria shares the stage with a long list — and more than one may coexist.[1]

Three classical pitfalls to anticipate on an MCQ or viva: [1]

• Malaria + dengue co-infection is common in India — a positive dengue NS1 does not exclude malaria; send both films.
• Malaria + bacterial septicaemia ("algid malaria") — a smear-positive patient in shock should receive IV artesunate AND empirical broad-spectrum antibiotics within the hour.
• Typhoid with thrombocytopenia or scrub typhus with splenomegaly can perfectly mimic malaria — the smear (and the eschar) are decisive. [1]

Clinical & Bedside Assessment

ABCDE first, with particular attention to: [1]

• Airway/Breathing — respiratory rate (the most sensitive marker of severity in children), SpO2, work of breathing, Kussmaul breathing (acidosis), crackles (pulmonary oedema/ARDS).
• Circulation — pulse, BP, capillary refill, postural drop (occult hypovolaemia), jugular venous pressure.
• Disability — Blantyre Coma Score (children) or GCS (adults); pupils, blood glucose at the bedside (every hour in severe disease, especially on quinine), look for retinal changes (malarial retinopathy).[66]
• Exposure — full skin exam (rash, eschar, bleeding, jaundice, pallor), abdominal exam for splenomegaly (soft, tender) and hepatomegaly, look for neck stiffness (always exclude meningitis in an unconscious malaria patient — lumbar puncture once safe). [1]

Named bedside findings worth knowing: [1]

• Malarial retinopathy — fundus signs with diagnostic value in cerebral malaria; identifying them is trainable even for non-ophthalmologists in endemic settings.[66]
• Hepatosplenomegaly with mild jaundice and pallor in a returned traveller — think malaria (also kala-azar, haemolytic anaemia, lymphoma).
• Tachypnoea with deep breathing = metabolic acidosis (poor prognostic marker — blood lactate over 5 mmol/L predicts death).[15]
• Cold peripheries with weak pulse = "algid malaria" (look for bacteraemia).
• Dark urine with pallor and jaundice = blackwater fever.[12]

History to extract in five questions: [1]

1. Travel history — exact countries, dates, compliance with chemoprophylaxis, mosquito-avoidance measures, blood transfusion in the past 3 months.
2. Fever pattern — onset, periodicity, rigors, sweating; remember the cycle is often irregular.
3. Symptoms of severe disease — confusion, drowsiness, seizures, breathlessness, dark urine, bleeding.
4. Pregnancy / comorbidity — splenectomy, sickle cell, HIV, diabetes, cardiac disease.
5. Prior malaria / treatment so far — drug names and doses (resistance, recrudescence). [1]

Investigations

Tier 1 — confirm the parasite (and rule in/out falciparum):[1]

• Thick blood film (3 drops, no fixation, Giemsa/Field stain) — the gold standard for DETECTION; 20 to 40 times more sensitive than thin film because the RBCs are lysed and many fields are scanned; sensitivity down to around 50 to 100 parasites/μL.
• Thin blood film (fixed with methanol, Giemsa) — SPECIES IDENTIFICATION and parasitaemia quantification. Examine for ring forms, trophozoite morphology, Schüffner dots, schizonts, gametocytes (banana-shaped = falciparum). Three smears at 12- to 24-hour intervals are required before declaring a patient smear-negative.
• Rapid Diagnostic Test (RDT) — immunochromatographic on finger-prick blood:
  • HRP-2 (histidine-rich protein 2) — P. falciparum only; persists for weeks after treatment (so cannot diagnose a treatment failure or new infection). Note HRP-2 gene deletions in parts of South America, Africa and India make some falciparum strains HRP-2-negative.
  • pLDH (parasite lactate dehydrogenase) — species-specific and clears in 1 to 2 weeks (better for treatment response).
  • Aldolase — pan-malarial.
• PCR — most sensitive and specific; distinguishes species and mixed infections; used for confirmation, research and outbreak investigation. Not point-of-care. [1]

How to calculate parasitaemia (%) on a thin film: [1]

• Count parasitised RBCs per 1,000 RBCs; multiply by 100 for percentage.
• Or: parasites/μL = (parasites counted / WBC counted) × 8,000 (using a thick film).
• Hyperparasitaemia = over 2 per cent (low transmission), over 10 per cent (hyperendemic), or over 4 per cent in pregnancy — consider exchange transfusion above 10 per cent with severe disease.[4]

Species morphological clues (a high-yield table): [1]

Tier 2 — assess severity and complications (admitted / severe patient):[4]

• Full blood count — anaemia (malarial anaemia is multifactorial: haemolysis, dyserythropoiesis and impaired erythropoiesis)[62]; thrombocytopenia is among the strongest routine blood-test markers of malaria[49]; neutrophilia suggests concomitant bacterial sepsis.
• Blood glucose — hypoglycaemia (under 2.2 mmol/L) is a defining feature of severe malaria and carries a high case fatality; recheck on quinine.[14]
• U&E + creatinine — acute kidney injury complicates up to 45.5 per cent of severe malaria in adults (pooled incidence about 26.5 per cent of all adult malaria admissions).[19]
• Venous lactate — lactate over 5 mmol/L predicts death as well as any clinical feature.[15]
• Coagulation — PT, aPTT, fibrinogen, D-dimer; coagulation activation accompanies sequestration in cerebral malaria.[9]
• G6PD assay — mandatory before primaquine or tafenoquine (haemolysis risk in deficiency).[31]
• Blood cultures — concomitant bacteraemia occurs in about 6 per cent of hospitalised African children with severe falciparum malaria; in adults it is uncommon (about 1 per cent in a Vietnamese series) but trebles the risk of death.[21]
• Urine — dipstick for haemoglobinuria (blackwater)[12]; pregnancy test in any woman of reproductive age.
• ECG (on quinoline antimalarials — QTc prolongation).[13]

Tier 3 — special situations: [1]

• Lumbar puncture if any meningism or persistent altered consciousness — to exclude bacterial meningitis (do CT first if focal signs or papilloedema).
• USS abdomen if suspected splenic rupture (sudden abdominal pain + shoulder-tip + falling haematocrit in vivax malaria). [1]

Severity criteria — any one feature defines severe malaria (and triggers IV artesunate + ICU):[2][15]

• Cerebral malaria: unrousable coma — Blantyre coma score 2 or less in children.[15][16]
• Impaired consciousness (any degree) or multiple seizures: impaired consciousness carries an odds ratio of 4.4 for death in African children.[15]
• Respiratory distress (acidotic breathing) — odds ratio 2.4 for death; the most sensitive clinical predictor of a fatal outcome.[15]
• Jaundice — odds ratio 1.9 for death.[15]
• Hypoglycaemia: glucose under 2.2 mmol/L.[14]
• Acidosis: blood lactate over 5 mmol/L.[15]
• Renal failure: odds ratio 11.1 for death in African children; AKI is an independent mortality predictor in adults.[15][4]
• Severe anaemia: Hb under 5 g/dL in African children.[17]
• ARDS / pulmonary oedema and liver dysfunction: mortality-associated in adult cohorts from India.[58]
• Shock ("algid malaria"): severe-sepsis-like picture, especially in non-immune adults.[54]
• Hyperparasitaemia: over 10 per cent with organ complications.[44]
• Haemoglobinuria (blackwater).[12]

Management — Resuscitation

Severe malaria is a medical emergency: the dose of IV artesunate must be drawn up the moment the diagnosis is suspected — do NOT wait for parasitaemia results.[2][4]

1. ABCDE. Airway protection, breathing and circulation assessment; secure two large-bore IV lines; cross-match; do not delay antimalarial therapy for any test.[4]
2. Stat IV artesunate. 2.4 mg/kg IV at 0, 12 and 24 h, then once daily until oral therapy is tolerated.[2] Children under 20 kg: 3 mg/kg per dose — the WHO-recommended paediatric dose since 2015.[22]
   • If artesunate is unavailable for the first 24 h: IV quinine 20 mg salt/kg loading dose infused over 4 h, then 10 mg/kg three times a day — switch to artesunate as soon as it arrives.[2]
3. Bedside glucose. Treat hypoglycaemia (under 2.2 mmol/L) immediately with IV dextrose — hypoglycaemic children had a case fatality of 61.5 per cent in one prospective series, and quinine drives hypoglycaemia (relative risk 3.2 in SEAQUAMAT).[14][2]
4. Fluids — cautiously. Bolus resuscitation with 20 to 40 mL/kg of albumin or saline increased 48-hour mortality in the FEAST trial of African children with severe febrile illness (57 per cent had malaria); give maintenance fluids and treat anaemia and hypoglycaemia rather than routine boluses.[20]
5. Seizures — treat promptly: convulsions, acidosis and hypoglycaemia all impair consciousness in cerebral malaria.[5]
6. Severe anaemia — transfuse; whole blood at a target volume of 20 mL/kg was the standard transfusion in a multicentre African series.[18]
7. Acidosis — lactate over 5 mmol/L predicts death; treat the cause (anaemia, hypovolaemia, sepsis).[15]
8. AKI — renal replacement therapy reduces mortality in severe-malaria AKI.[4]
9. ARDS / pulmonary oedema — lung-protective ventilation; avoid fluid overload.[20]
10. Shock / algid malaria — all children with severe malaria should receive broad-spectrum antibiotics in addition to parenteral artesunate (concomitant bacteraemia); in adults reserve empirical antibiotics for shock, jaundice, renal failure or hyperparasitaemia.[21]
11. Hyperparasitaemia over 10 per cent with organ complications — historically an indication for exchange transfusion, though case-control data show no survival advantage over artesunate-based chemotherapy alone.[44][45]
12. Pre-referral — where parenteral therapy is inaccessible, a single rectal artesunate suppository (10 mg/kg) is recommended before transfer.[55]
13. Monitor — artesunate clears parasites faster than quinine, the basis of its survival benefit in adults and African children; reassess parasite counts, glucose and consciousness repeatedly in the first 48 h.[2][3]

[2] [22] [14] [20] [44]

Management — Definitive & Stepwise

Strategy is driven by (1) species — falciparum/knowlesi vs vivax/ovale vs malariae; (2) severity — uncomplicated vs severe; (3) special situations — pregnancy, children, splenectomy, G6PD deficiency, prior treatment.[1]

Uncomplicated P. falciparum (and P. knowlesi) — ACT, 3 days

The WHO mandates artemisinin-based combination therapy (ACT) as first-line — the artemisinin partner clears parasites rapidly (10,000-fold reduction per cycle), the partner drug (long half-life) clears the residual and protects the artemisinin against resistance.[1]

Artemether-lumefantrine (AL, Coartem) — first-line ACT in many national programmes, including India's north-eastern states:[41]

• Standard tablets contain 20 mg artemether plus 120 mg lumefantrine.[23]
• Weight-banded dosing: one tablet per dose for 5 to 14 kg and two tablets for 15 to 24 kg in paediatric trials;[26] adult regimens deliver 80 mg artemether with 480 mg lumefantrine per dose.[24]
• The standard regimen is twice daily for 3 days (six doses); once-daily dosing lowers lumefantrine exposure and must not be substituted.[25]
• Give with fatty food or milk — lumefantrine absorption is fat-dependent.[23][25]

Artesunate-amodiaquine (AS+AQ) — artesunate 4 mg/kg daily for 3 days with amodiaquine 25 mg/kg over 3 days; evaluated as a first-line combination in African trials.[33]

Dihydroartemisinin-piperaquine (DHA-PPQ) — given once daily for 3 days; low day-7 piperaquine concentrations predict recurrent infection.[35]

Artesunate-mefloquine (AS-MQ) — artesunate 4 mg/kg plus mefloquine 8 mg/kg daily for three consecutive days.[34]

Partner drugs and their characteristic adverse effects (high-yield): [1]

• Lumefantrine — QT prolongation (avoid with other QT drugs, grapefruit).[13]
• Amodiaquine — hepatotoxicity, agranulocytosis; avoid in HIV with efavirenz/zidovudine.
• Piperaquine — QT prolongation.
• Mefloquine — neuropsychiatric (anxiety, insomnia, vivid dreams, psychosis, seizures); avoid in epilepsy, depression.
• Quinine — cinchonism (tinnitus, deafness, headache, nausea), hypoglycaemia (insulin release), QT prolongation, blackwater fever.[12]

Uncomplicated P. vivax and P. ovale — blood-stage + radical cure

• Blood-stage (chloroquine-sensitive): chloroquine 25 mg base/kg over 3 days — the standard schizonticidal regimen.[32][33]
• ACT-based settings — primaquine radical cure is coadministered with chloroquine or with one of four ACTs (artemether-lumefantrine, artesunate-mefloquine, artesunate-amodiaquine, dihydroartemisinin-piperaquine).[63]
• Radical cure of hypnozoites — the WHO recommends primaquine 0.25 to 0.5 mg/kg daily for 14 days to prevent relapse.[30] Tafenoquine as a single 300 mg or higher dose (approved only with chloroquine coadministration) is an alternative — G6PD testing is mandatory before either drug because of haemolysis risk, and both are contraindicated in deficiency and in pregnancy.[31]

Uncomplicated P. malariae

• Treat as for chloroquine-sensitive vivax — chloroquine 25 mg base/kg over 3 days; no radical cure (no hypnozoite — only vivax and ovale form one).[32][31]

Severe P. vivax or P. knowlesi

• Treat as severe falciparum — the IV artesunate 2.4 mg/kg regimen.[2] Severe vivax malaria is increasingly recognised — vivax can cause severe disease, and severe AKI due to vivax is well described.[51][19]

Pregnancy — special drug selection

• First trimester (all species) — quinine plus clindamycin is the WHO-recommended first-line treatment. First-trimester artemisinin exposure was not associated with worse pregnancy outcomes in an individual-patient-data meta-analysis (adverse outcomes 5.7 per cent with artemisinins vs 8.9 per cent with non-artemisinins) — reassuring data, but quinine-clindamycin remains the recommendation.[26][27]
• Second and third trimester — ACT (artemether-lumefantrine) is first-line in about three-quarters of national guidelines; IV artesunate for severe disease (88.6 per cent of guidelines recommend it).[28]
• Radical cure with primaquine / tafenoquine is CONTRAINDICATED in pregnancy (foetal G6PD status unknown) — defer until after delivery; IPTp with sulfadoxine-pyrimethamine remains the preventive cornerstone in Africa.[29][57]

Step-down and discharge

• After IV artesunate: switch to a full course of oral ACT once the patient can tolerate oral and parasitaemia is falling (usually within 24 to 48 h); continue ACT for the full 3 days.
• Parasite clearance is typically within 48 to 72 h on artesunate. A parasitaemia still over 10 per cent at 24 h or any parasites at 72 h suggests artemisinin resistance (especially if from the Greater Mekong) — escalate to a second ACT and seek expert advice.[7][8]
• FBC after artesunate — post-artesunate delayed haemolysis affected 23 per cent of African children treated for severe malaria (with more than 15 per cent of them developing severe anaemia and/or infectious events); look for falling haemoglobin and rising lactate dehydrogenase.[53]

Chemoprophylaxis (for travellers from non-endemic areas)

[36] [37] [38] [39] [64]

Universal mosquito-avoidance — long sleeves and trousers at dusk and dawn, DEET (20 to 50 per cent) on exposed skin, permethrin-impregnated long-lasting insecticidal nets (LLIN), screened/air-conditioned accommodation. Insecticide spraying and insecticide-treated bed nets are the backbone of malaria vector control. [1]

Vaccine — RTS,S/AS01 (Mosquirix). First malaria vaccine recommended by WHO (2021) for children in moderate-to-high transmission areas of sub-Saharan Africa. Phase 3 trial: 4-dose schedule from 5 months of age; around 36 per cent efficacy against clinical malaria and 32 per cent against severe malaria over 4 years, with waning protection; modest impact on population-level mortality and an important addition to (not replacement for) existing tools.[10][11]

Specific Subtypes & Scenarios

Cerebral malaria

• Definition — unrousable coma not attributable to another cause, with P. falciparum asexual forms on smear; cerebral-malaria trials define it by a Blantyre coma score under 3 in children.[16]
• Presentation — a severe neurological complication that differs between African children and non-immune adults; it should be considered in anyone with impaired consciousness after recent travel in a malaria-endemic area, and fundoscopy may show malarial retinopathy, which has diagnostic value.[5][6][66]
• Pathology — cerebral capillaries and venules packed with sequestered PRBCs, ring haemorrhages, Dürck's granulomas, brain swelling; cytokine (TNF-alpha)–mediated blood–brain barrier disruption.[9]
• Management — IV artesunate, head elevation 30°, avoid unnecessary fluid, treat seizures and fever, exclude hypoglycaemia, monitor glucose hourly, watch for ARDS (often around day 2-3), do NOT give prophylactic phenobarbital, exclude bacterial meningitis by LP once the patient is stable.
• Outcome — survivors have an increased risk of neurological and cognitive deficits, behavioural difficulties and epilepsy, making cerebral malaria a leading cause of childhood neurodisability in Africa; case fatality in endemic-area series is 16 to 22 per cent.[6][16]

Severe malarial anaemia

• Predominantly children in high-transmission Africa — severe malarial anaemia is defined in paediatric studies as Hb under 5 g/dL, arising from multifactorial mechanisms (haemolysis, dyserythropoiesis, impaired erythropoietic recovery).[17][62]
• Manage with blood transfusion — whole blood at a target volume of 20 mL/kg in African children; balance the benefit against volume and safety risks.[18]

Blackwater fever

• Massive intravascular haemolysis with haemoglobinuria (dark red/black urine), classically associated with intermittent quinine in semi-immune individuals; modern antimalarials have reduced incidence.[12]
• Stop quinine; switch to artesunate; supportive care (renal support, transfusion); manage complications (AKI, DIC).

Malaria in pregnancy

• Higher parasitaemia (placental sequestration), hypoglycaemia (especially on quinine), pulmonary oedema, severe anaemia, miscarriage, stillbirth, low birth weight; peripheral smear underestimates true burden.
• Treat all falciparum malaria in pregnancy as severe if any severity criterion is met; IV artesunate (2nd/3rd trimester) or quinine + clindamycin (1st trimester).
• Sulphadoxine-pyrimethamine (SP) intermittent preventive treatment in pregnancy (IPTp) — at least 3 doses in the 2nd and 3rd trimester at antenatal visits in moderate-high transmission Africa. [1]

Congenital / transfusion-transmitted malaria

• Bypasses the hepatic stage; no hypnozoites (no relapse); incubation shorter (around 1 to 4 weeks).
• Treat with blood-stage therapy only (ACT for falciparum; chloroquine for vivax); no primaquine. [1]

Hyperreactive malarial splenomegaly (HMS / tropical splenomegaly syndrome)

• Chronic antigenic stimulation → polyclonal B-cell activation → high IgM, massive splenomegaly, pancytopenia; diagnosed by parasitaemia absent or scanty, IgM markedly raised, response to long-term antimalarial prophylaxis.
• Treat with long-term antimalarial prophylaxis (e.g. proguanil weekly). [1]

Mixed infections

• P. falciparum + P. vivax co-infection is common in India and Papua; the falciparum dominates severity but the vivax hypnozoite will relapse later — treat the falciparum with ACT AND give primaquine for the vivax after G6PD screening. [1]

P. knowlesi infection

• Zoonotic; macaque reservoir in Malaysia / Philippines; rapidly rising quotidian parasitaemia that can be fatal; morphologically mimics P. falciparum (early rings) and P. malariae (band forms); PCR or specific RDT needed; treat as for falciparum with IV artesunate if severe. [1]

Co-infection with bacterial sepsis ("algid malaria")

• A smear-positive patient in shock is not just malaria — bacteraemia (Gram-negative especially) coexists in a substantial minority; give artesunate AND empirical broad-spectrum antibiotics within the hour. [1]

Complications & Pitfalls

Specific organ complications (overlap with severity criteria above):[4]

• Cerebral: seizures, coma, post-malaria neurological syndrome (transient psychosis, ataxia, seizures 1 to 4 weeks after recovery), cognitive and behavioural sequelae in children.
• Pulmonary: ARDS — classically around day 2 to 3, may develop as the patient is otherwise improving; treat with lung-protective ventilation, avoid fluid overload.
• Renal: acute tubular necrosis / AKI, haemoglobinuric nephropathy, requiring RRT.
• Haematological: severe anaemia, DIC, splenic rupture (mainly vivax, especially after repeated palpation), post-artemisinin delayed haemolysis (PADH) — affected 23 per cent of African children treated with artesunate for severe malaria; check haemoglobin after treatment.[53]
• Metabolic: hypoglycaemia (parasite-driven AND quinine-induced), lactic acidosis (strongest mortality predictor).
• Cardiovascular: "algid malaria" — shock, often with concomitant bacteraemia.
• Obstetric: miscarriage, stillbirth, low birth weight, vertical transmission. [1]

Classic pitfalls (each costs an MCQ): [1]

• Diagnosing a febrile returning traveller with "flu" and not sending a malaria film — cerebral malaria must be considered in anybody with impaired consciousness who has recently travelled in a malaria-endemic area.[5]
• Sending one smear and declaring the patient malaria-free — multiple blood film preparations are required to exclude malaria; almost 7 per cent of diagnosed patients had an initially negative film, most later proven to have vivax.[47]
• Treating falciparum with chloroquine — chloroquine monotherapy has been rendered ineffective by resistance.[33]
• Giving primaquine or tafenoquine without a G6PD assay — G6PD testing is required first because of haemolysis risk.[31]
• Taking artemether-lumefantrine on an empty stomach — lumefantrine absorption is fat-dependent; give with milk or fatty food.[23][25]
• Forgetting the gametocyte — single low-dose primaquine (0.10 to 0.40 mg/kg) is gametocytocidal in falciparum malaria and reduces transmission.[56]
• Over-resuscitating fluids — bolus fluids (20 to 40 mL/kg) increased mortality in African children in the FEAST trial.[20]
• Missing concomitant bacteraemia in "algid" malaria — all children with severe malaria should also receive broad-spectrum antibiotics.[21]
• Misreading P. knowlesi as P. falciparum or P. malariae on microscopy — most reported cases were misidentified; RDTs often fail and confirmation is molecular.[52]

Prognosis & Disposition

Uncomplicated malaria treated with ACT — cure within 3 days; case-fatality under 0.1 per cent. Treated vivax can still relapse unless primaquine radical cure is given (and the patient completes the 14-day course).[1]

Severe falciparum — even with optimal artesunate, mortality is 8 to 15 per cent overall and rises sharply with coma (cerebral malaria 15 to 20 per cent), ARDS (over 50 per cent), metabolic acidosis (lactate over 5), renal failure, and high parasitaemia (over 10 per cent). Children may have residual epilepsy, motor deficits, cognitive impairment, behavioural problems.[2][6]

Disposition: [1]

• Uncomplicated — oral ACT as an outpatient only if (a) smear confirmed non-falciparum or low-parasitaemia falciparum, (b) no severity criterion, (c) reliable follow-up at 48-72 h, (d) tolerating oral therapy. Admit any semi-immune traveller, pregnant woman, child under 5, or anyone without reliable follow-up.
• Severe — ICU; transfer to a higher centre if no ICU/ICU capability locally; IV artesunate should be started before transfer.
• Follow-up — repeat smear at 48-72 h (parasitaemia should be falling), clinical review at day 7, FBC at week 2 and 4 (post-artemisinin haemolysis), counsel on recurrence vs relapse vs reinfection. [1]

Special Populations

• Children (weight-based dosing) — IV artesunate 3 mg/kg per dose if under 20 kg (WHO recommendation since 2015).[22] African children with severe malaria present predominantly with severe anaemia, hypoglycaemia, cerebral malaria and seizures, and respiratory distress usually reflects lactic acidosis.[54] Avoid fluid boluses (FEAST — excess mortality).[20]
• Pregnancy — quinine plus clindamycin in the first trimester, ACT (artemether-lumefantrine) and IV artesunate for severe disease in later trimesters;[26][28] no primaquine or tafenoquine (foetal G6PD unknown)[29]; IPTp-SP is the preventive cornerstone in Africa.[57]
• Older travellers — older adults are more likely to suffer severe complications from malaria; antimalarial drug interactions accumulate with age.[59]
• Asplenic / hyposplenic — severe malaria (including severe vivax with shock, prostration and AKI) is reported after splenectomy; treat any smear-positive asplenic patient as high risk.[60]
• Returning traveller to a non-endemic country — non-immune adults are the classic cerebral-malaria group; consider malaria in any impaired consciousness after endemic-area travel.[5]
• G6PD deficiency — primaquine and tafenoquine are contraindicated in deficiency (haemolysis); screen before either drug.[31]

Evidence, Guidelines & Regional Differences

Landmark trials every MBBS student should know: [1]

• SEAQUAMAT (Dondorp 2005, Lancet) — Southeast Asian trial of IV artesunate vs quinine in severe falciparum. Mortality 22 per cent (quinine) vs 15 per cent (artesunate) — a 35 per cent relative reduction. Established IV artesunate as the global standard for severe malaria in adults.[2]
• AQUAMAT (Dondorp 2010, Lancet) — African children with severe falciparum. Mortality 8.5 per cent (artesunate) vs 10.9 per cent (quinine) — a 22.5 per cent relative reduction. Extended the artesunate standard to African children.[3]
• Dondorp 2009 (NEJM) — first definitive description of artemisinin resistance in western Cambodia (slow parasite clearance).[7]
• Ashley 2014 (NEJM, TRAC) — spread of artemisinin resistance across the Greater Mekong subregion; ring-stage reduction in susceptibility; mechanistically linked to kelch-13 (K13) propeller mutations. Drives the shift to longer ACT courses and triple ACTs.[8]
• Wassmer 2013 (Blood) — loss of endothelial protein C receptor links coagulation, inflammation and sequestration in cerebral malaria.[9]
• RTS,S phase 3 (Lancet 2015) — first malaria vaccine to show efficacy (around 36 per cent clinical, 32 per cent severe over 4 years; waning protection); WHO recommended in 2021; pilot implementation ongoing in Ghana, Kenya, Malawi.[10][11]
• FEAST (Maitland 2011, NEJM) — bolus fluid resuscitation in African children with severe febrile illness (including malaria) increased mortality — practice-changing for fluid therapy.

[1]

Controversies and emerging issues: [1]

• Artemisinin resistance — slow parasite clearance, strongly associated with K13 (kelch-13) propeller mutations, has spread across the Greater Mekong subregion, threatening the ACT backbone.[8][7]
• Exchange transfusion — historically indicated above 10 per cent parasitaemia with organ complications;[44] case-control data show no survival advantage over artesunate-based chemotherapy.[45]
• Targeted adjuncts in cerebral malaria — including dexamethasone and mannitol — are not beneficial.[4]
• Pre-referral rectal artesunate — a single 10 mg/kg suppository is recommended for severely ill children where parenteral therapy is inaccessible; pharmacokinetic data support the dose.[55]
• Tafenoquine vs primaquine for vivax radical cure — single-dose tafenoquine (300 mg or higher, approved only with chloroquine) versus the primaquine 0.25 to 0.5 mg/kg daily, 14-day course; both strictly require G6PD testing and are contraindicated in deficiency and pregnancy.[31][29]
• Vaccines — RTS,S/AS01 is WHO-recommended for African children;[10][11] the R21/Matrix-M vaccine showed over 75 per cent efficacy in phase 2b and has completed a large phase 3 trial.[46]

Exam Pearls

• Thick film for DETECTION — the microscopy reference standard; thin film for PARASITAEMIA quantification — RDTs are less sensitive than expert thick film.[65]
• Multiple blood films are required to exclude malaria — about 7 per cent of patients have an initially negative film.[47]
• HRP2-based RDTs detect falciparum (pLDH tests are species-panel based).[61]
• P. falciparum is the most severe species — cytoadherence mediated by PfEMP1, which undergoes antigenic variation.[48]
• Hypnozoites (only vivax and ovale) — relapse requires 8-aminoquinoline radical cure.[31]
• ACT — first-line for uncomplicated falciparum; artemether-lumefantrine twice daily for 3 days, with fatty food.[25]
• IV artesunate 2.4 mg/kg at 0, 12, 24 h then daily for severe — 3 mg/kg per dose if under 20 kg.[2][22]
• Primaquine / tafenoquine — G6PD screen first; haemolysis in deficiency.[31]
• Quinine — hypoglycaemia (relative risk 3.2 in SEAQUAMAT); blackwater fever is classically associated with intermittent quinine.[2][12]
• Mefloquine — neuropsychiatric adverse effects.[39]
• Cerebral malaria — case fatality 16 to 22 per cent in endemic-area series.[16]
• Hypoglycaemia (under 2.2 mmol/L) — a defining feature of severe malaria with very high case fatality.[14]
• Thrombocytopenia is among the strongest routine blood-test clues to malaria.[49]
• Post-artemisinin delayed haemolysis — affected 23 per cent of African children treated with artesunate for severe malaria; recheck haemoglobin after treatment.[53]
• Kelch-13 (K13) mutations — markers of artemisinin resistance (Greater Mekong).[8]
• Quartan malaria (malariae) — immune-complex glomerulonephritis and nephrotic syndrome, progressing slowly even after parasite clearance.[50]
• Vaccine — RTS,S/AS01 (WHO-recommended) and R21/Matrix-M (over 75 per cent efficacy in phase 2b).[10][46]

Ward-round test

Stem 1. A returned traveller is febrile with a positive thick film. The thin film shows delicate ring forms, multiple rings per cell, and a banana-shaped gametocyte. Which species is it, and what is the first-line treatment if she has no severity criteria?[1]

Show the answer

Plasmodium falciparum — the multiple rings per cell, the accolé/appliqué forms, and the crescent (banana-shaped) gametocyte are diagnostic. Treat uncomplicated falciparum with an artemisinin-based combination therapy: artemether-lumefantrine, four tablets twice daily for three days (six doses over 60 hours), taken with fatty food to secure lumefantrine absorption.[1]

Stem 2. The same patient becomes drowsy and her bedside glucose reads 1.8 mmol/L. Name the drug, the dose, and the bedside number that defines severe hypoglycaemia.[2]

Show the answer

This is severe falciparum malaria. Give intravenous artesunate 2.4 mg/kg at 0, 12 and 24 hours then once daily (3 mg/kg per dose if under 20 kg), admit to ICU, and treat the hypoglycaemia with intravenous dextrose.[2][22] Severe hypoglycaemia is defined by a bedside glucose under 2.2 mmol/L — hypoglycaemic children in one series had a case fatality of 61.5 per cent, and quinine itself drives hypoglycaemia (relative risk 3.2 in SEAQUAMAT), so glucose must be rechecked repeatedly.[14][2]

Stem 3. A man is treated for vivax malaria with chloroquine alone and sent home. Six weeks later he is febrile again with parasites on the smear. Why, and what was omitted from his treatment?[1]

Show the answer

This is a relapse from dormant hypnozoites in the liver — only P. vivax and P. ovale form hypnozoites, and they require an 8-aminoquinoline (primaquine or tafenoquine) for radical cure.[31] The omission was primaquine 0.25 to 0.5 mg/kg daily for 14 days, which must follow G6PD testing because it causes severe haemolysis in deficient patients.[30][31]

Exam application bank (NEET-PG / INICET)

One-line answer

Malaria is a mosquito-borne protozoan illness caused by the apicomplexan parasite Plasmodium and transmitted by the bite of an infected female Anopheles mosquito. Five species infect humans — P. falciparum (most lethal), P. vivax (commonest relapsing form), P. ovale, P. malariae and the zoonotic P. knowlesi. Classical presentation is a fever paroxysm (cold, hot and sweating stages) with chills, rigors, headache and splenomegaly, but in many endemic areas the periodicity is irregular and the illness is indistinguishable from other febrile syndromes. P. falciparum causes severe malaria — cerebral malaria, severe malarial anaemia, ARDS, acute kidney injury, hypoglycaemia and acidosis — through cytoadherence, sequestration and rosetting of parasitised erythrocytes in the microvasculature. Diagnosis is by thick blood film (detection sensitivity) and thin film (species identifica

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Malaria.

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