Malaria: a complete clinical chapter for student doctors
Malaria is an infection caused by protozoa of the genus Plasmodium and transmitted predominantly by the bite of an infected female Anopheles mosquito. It is one of the most important causes of fever, anaemia, hospital admission and preventable death in Uganda. The clinician’s task is not simply to recognise a positive test: it is to identify the species and parasite burden, recognise severe disease early, treat correctly, and continue searching for another diagnosis when the course does not fit malaria.
Clinical anchor: every febrile patient may have malaria, but every positive malaria test does not explain every clinical problem.
Learning outcomes
- Describe the vector, human and mosquito phases of the parasite life cycle.
- Explain why P. falciparum causes sequestration, cerebral malaria, acidosis, anaemia, hypoglycaemia and renal injury.
- Differentiate uncomplicated malaria, severe malaria, treatment failure and non-malarial fever.
- Interpret thick and thin films, rapid diagnostic tests, parasite density and repeat tests.
- Manage malaria safely in children, pregnancy, HIV, malnutrition, sickle-cell disease and renal dysfunction.
- Explain prevention, surveillance, counselling and follow-up.
Definition and species
Malaria is confirmed when a compatible clinical illness is accompanied by asexual Plasmodium parasites in blood or a validated parasite antigen test. Five species infect humans:
| Species | Biology | Clinical importance | Microscopy clues |
|---|---|---|---|
| P. falciparum | Multiple parasites per red cell; mature forms sequester | Most severe disease; cerebral malaria, acidosis, renal failure, severe anaemia, shock and death | Delicate multiple rings, appliqué forms, crescent gametocytes; mature trophozoites often absent from peripheral film |
| P. vivax | Invades reticulocytes; dormant hypnozoites | Relapse, splenic complications and occasional severe disease | Enlarged red cells, Schüffner dots, amoeboid trophozoites |
| P. ovale | Hypnozoites; usually low parasitaemia | Relapsing illness; can be misidentified as vivax | Oval/fimbriated erythrocytes, Schüffner-type dots |
| P. malariae | Low-level long persistence | Quartan pattern and chronic immune-complex nephropathy | Band forms and rosette schizonts |
| P. knowlesi | Twenty-four-hour asexual cycle; macaque reservoir | Rapidly progressive severe disease in Southeast Asia | May resemble falciparum early and malariae later; travel history is essential |
Uganda epidemiology and determinants of risk
Transmission intensity varies between regions and seasons. Rainfall and temperature affect breeding sites; altitude changes vector survival; housing, drainage, bed-net access and indoor residual spraying affect exposure. Repeated childhood infection can create partial immunity, but no endemic adult is completely protected. Severe disease is more likely in young children, pregnant women, non-immune visitors, people with HIV or malnutrition, and patients with sickle-cell disease or delayed access to treatment.
Ask about residence, recent travel, season, occupation near water or forest, bed-net use, indoor spraying, previous malaria, recent antimalarial use and whether medicine was purchased from an informal source. An epidemiological risk does not replace parasitological testing; a low-risk patient can still have imported or transfusion-associated malaria.
Transmission and life cycle
- Inoculation: the mosquito injects sporozoites with saliva.
- Hepatic invasion: sporozoites rapidly enter hepatocytes. Asexual multiplication forms liver schizonts, which rupture and release merozoites. This phase is clinically silent.
- Hypnozoites: P. vivax and P. ovale may remain dormant in hepatocytes and reactivate, producing relapses without a new mosquito bite.
- Erythrocytic cycle: merozoites invade red cells, develop through ring, trophozoite and schizont stages, and rupture the cell. The cycle is approximately 48 hours for falciparum/vivax/ovale and 72 hours for malariae.
- Gametocytogenesis: a proportion differentiates into male and female gametocytes, which are the forms infectious to mosquitoes.
- Mosquito development: gametocytes fuse in the gut, form an ookinete and oocyst, and generate sporozoites that migrate to the salivary glands.
Pathophysiology in detail
Fever
Rupture of schizont-infected erythrocytes releases parasite products such as glycosylphosphatidylinositol and haemozoin. Innate immune cells produce IL-1, IL-6, TNF and other mediators, causing rigors, fever, sweating and malaise. Antipyretics improve comfort but do not treat the parasite.
Sequestration and microvascular disease
Falciparum-infected erythrocytes express PfEMP1 and related adhesins. They bind endothelial receptors, form rosettes with uninfected cells and avoid splenic clearance. In the brain, placenta, kidneys and lungs this reduces perfusion and oxygen delivery. Sequestration explains why peripheral parasite density may underestimate total biomass.
Anaemia
Both infected and uninfected erythrocytes are removed by the spleen. Inflammation, dyserythropoiesis, bleeding, nutritional deficiency and repeated infection worsen anaemia. Severe anaemia reduces oxygen delivery and can itself cause heart failure, acidosis and death.
Cerebral malaria
Microvascular obstruction, endothelial activation, blood-brain barrier dysfunction, hypoxia and inflammatory injury produce impaired consciousness, seizures and coma. Cerebral malaria is a clinical diagnosis in a patient with falciparum parasitaemia after alternative causes of coma have been assessed; a positive malaria test must not stop evaluation for meningitis, hypoglycaemia, sepsis, intoxication or head injury.
Acidosis and respiratory distress
Lactate accumulates because of tissue hypoxia, anaerobic metabolism, severe anaemia, seizures, shock and impaired hepatic/renal clearance. Deep breathing is often compensatory Kussmaul breathing, not primary pneumonia. Pulmonary oedema may follow capillary leak or excessive fluid administration.
Hypoglycaemia
Glucose is consumed by parasites and sick patients often have poor intake. Hepatic dysfunction, quinine-related hyperinsulinaemia and pregnancy further increase risk. Neurological signs of hypoglycaemia can mimic cerebral malaria.
Renal and hepatic injury
Hypoperfusion, haemoglobinuria, inflammatory injury and parasite pigment can cause acute kidney injury. Jaundice may result from haemolysis, hepatocellular injury or cholestasis; marked jaundice with encephalopathy should trigger consideration of severe malaria plus hepatic failure or another diagnosis.
Clinical presentation
Uncomplicated malaria
The typical patient has fever or a history of fever, chills, rigors, headache, weakness, myalgia, arthralgia, anorexia, nausea or vomiting. Abdominal pain and diarrhoea are common in children. The spleen may be palpable. Fever periodicity is often absent, especially early or after partial treatment.
Severe malaria danger signs
- Impaired consciousness, coma, abnormal behaviour or repeated convulsions.
- Prostration: inability to sit, stand, drink or breastfeed.
- Respiratory distress, acidotic breathing, hypoxaemia or pulmonary oedema.
- Shock, cold extremities, weak pulse or delayed capillary refill.
- Severe pallor, haemoglobinuria, jaundice with organ dysfunction or abnormal bleeding.
- Hypoglycaemia, oliguria, acute kidney injury or severe electrolyte disturbance.
- Persistent vomiting, very high parasite density or rapid clinical deterioration.
Children
Children may not describe fever. Look for poor feeding, lethargy, irritability, repeated vomiting, convulsions, inability to sit, severe pallor, deep breathing, hypoglycaemia and dehydration. A child can have severe malaria without a high measured temperature after antipyretics.
Pregnancy
Placental sequestration contributes to maternal anaemia, fetal growth restriction, miscarriage, stillbirth, prematurity and low birth weight. Symptoms may be atypical. Check fetal wellbeing while treating the mother; do not delay effective therapy because of trimester concerns when malaria is severe.
Clinical assessment: an exam and ward method
- ABCDE: airway, breathing, circulation, disability and exposure.
- Disability: mental status, GCS/Blantyre score, pupils, seizures and bedside glucose.
- Circulation: pulse, blood pressure, capillary refill, peripheral temperature, hydration, urine output and shock.
- Exposure: temperature, pallor, jaundice, rash, bleeding, splenomegaly, meningism, chest signs and obstetric examination.
- Context: age/weight, pregnancy, HIV, malnutrition, sickle-cell disease, recent antimalarial exposure and alternative infection risk.
Record baseline weight, time of first dose, parasite test, glucose, haemoglobin, urine output and neurological status. These measurements make deterioration or response visible.
Diagnosis
Microscopy
A thick film concentrates blood and is more sensitive for low parasite density. A thin film preserves red-cell morphology and helps identify species, developmental stage and percentage parasitaemia. Films should be prepared before treatment when this does not delay therapy and should be read by trained staff with quality control.
Rapid diagnostic tests
HRP2-based tests detect a falciparum antigen that can persist after clearance and may be falsely negative with HRP2-deleted parasites. pLDH-based tests generally correlate more closely with viable parasites but also have sensitivity limits. Record the test type and result; do not treat an RDT as a severity measure.
Parasite density and repeat tests
In severe disease quantify parasites where possible and repeat films according to facility protocol, often at 12–24-hour intervals until a clear fall. A persistent positive HRP2 RDT alone does not prove treatment failure. Persistent asexual parasitaemia, rising density, clinical deterioration or recurrence after an appropriate interval requires a treatment-failure assessment.
Supportive investigations
| Investigation | Why it matters | Interpretation |
|---|---|---|
| FBC/film | Anaemia, thrombocytopenia, leukocytosis | Severe anaemia may explain respiratory distress; thrombocytopenia is common but does not by itself prove DIC. |
| Glucose | Rapidly reversible cause of coma/seizures | Check at presentation and repeatedly in severe illness, pregnancy and children. |
| Urea, creatinine, electrolytes | AKI and fluid/renal dosing | Rising creatinine or oliguria requires strict fluid and nephrotoxin management. |
| Bilirubin/LFTs | Haemolysis, cholestasis, hepatic injury | Marked jaundice with organ dysfunction signals severe disease or co-pathology. |
| Blood gas/lactate | Acidosis and tissue hypoperfusion | Deep breathing and high lactate indicate high risk. |
| Culture/other tests | Sepsis, meningitis, pneumonia, UTI and co-infection | Do not withhold antibiotics when bacterial infection is plausible. |
Differential diagnosis of fever
Depending on age, geography and syndrome, consider bacterial sepsis, meningitis, pneumonia, typhoid, urinary infection, brucellosis, relapsing fever, dengue, viral haemorrhagic fever, HIV-related infections, tuberculosis, sickle-cell crisis, acute leukaemia, drug fever and abscess. In a child with diarrhoea, dehydration and malaria positivity, assess for invasive bacterial disease rather than attributing all signs to malaria.
Uncomplicated malaria treatment
Use a current UCG-recommended ACT and the patient’s measured weight. Artemether–lumefantrine (AL 20/120 mg) is commonly first-line in Uganda and is administered as six doses over three days in weight bands. Give each dose with food or breast milk containing fat. If vomiting occurs soon after a dose, repeat according to the UCG instructions; persistent vomiting is an admission/referral indication.
Before giving ACT
- Confirm no danger sign, severe anaemia, shock or inability to swallow.
- Ask about recent ACT, quinine, vomiting and drug allergies.
- Calculate dose by weight, not by age alone.
- Explain the six-dose schedule and the need for adherence.
During treatment
- Give with food; do not use artemisinin monotherapy.
- Use paracetamol for distressing fever; maintain hydration and nutrition.
- Review if symptoms worsen or have not begun to improve within 24–48 hours.
- Check for a different infection if fever persists.
After treatment
- Return immediately for confusion, convulsions, breathing difficulty, persistent vomiting or inability to drink.
- Re-test for suspected treatment failure and document the regimen.
- Relapsing vivax/ovale disease requires a separate radical-cure decision.
Severe malaria emergency protocol
- Airway and breathing: position safely, suction if needed, give oxygen for hypoxaemia, prepare for assisted ventilation in coma or pulmonary oedema.
- Circulation: obtain IV access, take blood, assess shock and avoid indiscriminate large fluid boluses. Severe malaria hearts and kidneys may not tolerate overload.
- Glucose: check immediately; give IV dextrose for hypoglycaemia and recheck frequently.
- Artesunate: give IV artesunate using the current UCG/WHO weight-based schedule, commonly at 0, 12 and 24 hours then daily until oral therapy is possible. Children under 20 kg may require the higher WHO weight-based dose. Use IM artesunate if IV access is unavailable and transfer urgently according to protocol.
- Completion therapy: once the patient has received at least 24 hours of parenteral treatment and can swallow, complete a full three-day oral ACT.
- Neurology: treat prolonged/recurrent seizures with protocol anticonvulsant, check glucose, and investigate meningitis or other causes of coma.
- Anaemia: FBC, group and cross-match; transfuse based on haemoglobin, respiratory compromise, shock and local protocol.
- Renal failure: catheterise when indicated, measure hourly urine, monitor potassium/acid-base status, stop nephrotoxins and refer for dialysis when needed.
- Sepsis: give empiric antibiotics when bacterial meningitis/sepsis cannot be excluded, especially in children with severe illness.
- Haemolysis surveillance: check haemoglobin after artesunate in severe/prolonged cases because delayed haemolysis can occur.
Management of specific severe complications
Cerebral malaria
Protect the airway, position laterally, check glucose, treat seizures, maintain normoxia and normocapnia, avoid unnecessary sedation, and search for meningitis. Do not perform lumbar puncture in raised intracranial pressure or unstable coma.
Severe anaemia
Assess work of breathing, heart failure, bleeding, haemolysis and nutritional causes. Transfusion decisions must combine haemoglobin with clinical compromise and local blood-safety protocol. Give oxygen only as indicated and monitor for overload.
Shock and acidosis
Look for sepsis, dehydration, bleeding and myocardial dysfunction. Use small reassessed fluid aliquots when indicated rather than routine aggressive fluids. Lactate, capillary refill, urine output and mental state guide response.
Acute kidney injury
Monitor input/output, creatinine, potassium, bicarbonate and pulmonary status. Avoid NSAIDs and nephrotoxic antibiotics when alternatives exist. Dialysis is indicated for refractory hyperkalaemia, acidosis, pulmonary oedema, uraemia or persistent severe azotaemia.
Pulmonary oedema
Stop excess fluids, sit the patient up, provide oxygen/positive pressure and seek critical-care support. Consider cardiac/renal dysfunction and severe anaemia.
Special populations and interactions
Pregnancy
Any trimester can receive parenteral artesunate for severe malaria; the mother’s survival is the priority. Transition to an effective ACT once oral therapy is tolerated, follow UCG/obstetric guidance and monitor glucose, haemoglobin, fetal status and uterine contractions.
Children
Use accurate weight, dispersible formulations, glucose monitoring, seizure readiness and careful fluids. A child with repeated vomiting, severe pallor or altered consciousness requires admission even if the first RDT is negative or unavailable.
HIV and antiretroviral therapy
Review cotrimoxazole, efavirenz, protease inhibitors and other medicines for interactions and overlapping hepatic/renal toxicity. HIV increases risk of severe and recurrent malaria.
Malnutrition and sickle-cell disease
Assess hypoglycaemia, electrolyte abnormalities, anaemia and infection. Sickle-cell patients may have malaria plus haemolytic crisis; do not assume one diagnosis explains all symptoms.
Treatment failure and recurrent malaria
Separate recrudescence (surviving parasites), reinfection (new mosquito infection), relapse (vivax/ovale hypnozoites) and a non-malarial illness. Ask for the exact drug, dose, schedule, vomiting, source and adherence. Repeat microscopy, assess parasite density and use the current Uganda treatment-failure algorithm. Refer recurrent, severe, pregnancy-associated, neurological or diagnostically uncertain cases.
Prevention and public health
- Long-lasting insecticidal nets every night; repair and replace damaged nets.
- Indoor residual spraying and environmental control of breeding sites.
- Antenatal intermittent preventive treatment with sulfadoxine–pyrimethamine according to national policy.
- Seasonal chemoprevention and other targeted national programmes when eligible.
- Prompt testing, effective treatment and reporting of clusters reduce transmission.
- Use screens, long sleeves and repellents as additional, not replacement, measures.
Clinical counselling
- Explain why finishing all ACT doses matters even after fever settles.
- Advise the patient not to share leftover antimalarials or use artemisinin monotherapy.
- Give clear danger signs and a return plan.
- Discuss net use, pregnancy prevention/intermittent treatment, and testing of other febrile household members.
Exam and OSCE pearls
- Thick film detects; thin film identifies.
- A positive HRP2 RDT may persist after cure, while a negative test can miss low density or HRP2-deleted parasites.
- Cerebral malaria requires glucose and meningitis/sepsis assessment.
- Hypoglycaemia is a common reversible cause of coma and must be checked repeatedly.
- Severe malaria is a diagnosis of severity, not merely a high fever.
- Parenteral artesunate is followed by a full oral ACT; the initial injections are not a complete course.
- Do not anchor on malaria when focal signs or persistent deterioration suggest co-infection.
References
- SlideShare: Malaria PPT.
- Uganda Clinical Guidelines: INF033.
- Uganda Clinical Guidelines: INF032.
- Uganda Clinical Guidelines 2023.
- WHO Guidelines for malaria.
- CDC: malaria evaluation and diagnosis.
- CDC: treatment of severe malaria.
Safety note: This is educational material. Confirm doses, formulations, referral thresholds and treatment-failure regimens against the latest UCG and Ministry of Health updates.
