Malaria

Related Subjects: |Fever in a traveller |Malaria Falciparum (Cerebral Malaria) |Malaria |Malaria in Children

🌍 About

• 🦟 Malaria is a notifiable potentially life-threatening infection caused by Plasmodium parasites, transmitted by infected female Anopheles mosquitoes. ⚡ Even when not fatal, malaria causes major debility, anaemia, school/work absence, reduced productivity and socioeconomic harm.
• 👶 The greatest global mortality burden is in young children, especially in sub-Saharan Africa; pregnant women and non-immune travellers are also high risk.🤒 Malaria is closely linked with poverty, poor housing, limited healthcare access, high infant mortality and chronic morbidity.
• 📖 See BNF for current UK treatment guidance

📜 Etymology

• The word malaria comes from Italian mala aria, meaning “bad air”, from the historical belief that the illness arose from marsh vapours.

🧬 Types of Plasmodium

• ⚫ P. falciparum: Deadliest species; causes most severe malaria and deaths, especially in Africa.
• 🟢 P. vivax: Relapses due to dormant liver hypnozoites; more common outside much of sub-Saharan Africa.
• 🟣 P. ovale: Similar to P. vivax; forms hypnozoites and can relapse.
• 🟡 P. malariae: Often milder but can persist for years; associated with quartan fever and rarely nephrotic syndrome.
• 🔴 P. knowlesi: Zoonotic malaria in Southeast Asia; 24-hour replication cycle, so it may progress rapidly and be misidentified as P. malariae.

⚠️ Risk Factors

• 👶 Infants and young children in endemic areas → highest risk of severe disease and death.
• 🤰 Pregnancy → increased risk of severe malaria, anaemia, miscarriage, stillbirth, low birth weight and maternal complications.
• ✈️ Non-immune travellers and migrants visiting friends/relatives in endemic regions → high risk if prophylaxis is omitted.
• 🧬 Sickle cell trait gives partial protection against severe P. falciparum malaria.
• 🩸 Duffy-negative blood group gives marked resistance to P. vivax, common in many African populations.
• 🔄 Repeated exposure may produce partial immunity, but it is incomplete and wanes after leaving endemic areas.

⏳ Incubation Periods

• ⚫ P. falciparum: usually 7–14 days, but may be longer, especially with partial prophylaxis.
• 🟢 P. vivax / P. ovale: usually 12–18 days, but relapse can occur months or years later from hypnozoites.
• 🟡 P. malariae: often 18 days to several weeks; can persist long-term.
• 🔴 P. knowlesi: often around 9–12 days.

🩺 Clinical Presentation

• 🌡️ Fever, chills, rigors and sweats; classic cyclical paroxysms may be absent, especially early or in imported malaria.
• 🤕 Headache, myalgia, malaise, nausea, vomiting, diarrhoea or cough.
• 🩸 Anaemia, jaundice, thrombocytopenia and splenomegaly may occur.
• ⚫ P. falciparum: severe complications include cerebral malaria, hypoglycaemia, severe anaemia, acidosis, renal failure, ARDS, shock and high parasitaemia.
• 📈 Chronic infection may cause splenomegaly and anaemia.
• 👶 Infants may have some early protection from maternal antibody and fetal haemoglobin, but young children remain the major severe-malaria risk group globally.

🔬 Investigations

• Urgent malaria testing is required in any febrile patient with relevant travel/exposure history.
• Microscopy:
  • 🧪 Thick film → most sensitive for detecting parasites.
  • 🔍 Thin film with Giemsa stain → species identification and parasitaemia quantification.
  • Repeat blood films if negative but suspicion remains high. In UK practice, consider daily films for 3 days while investigating other diagnoses.
• 💡 Rapid diagnostic tests: detect parasite antigens and are useful, but should not replace microscopy where available.
• 🧬 PCR: useful for species confirmation or low-level/mixed parasitaemia, but should not delay treatment in suspected severe malaria.
• 📊 Supportive tests: FBC, U&E/creatinine, LFTs/bilirubin, glucose, lactate/ABG or VBG if unwell, coagulation, group and save, and pregnancy test where relevant.

💊 Management

Treatment depends on Plasmodium species, severity, pregnancy status, prior prophylaxis/treatment and local resistance patterns. Seek infectious diseases/tropical medicine advice for imported malaria, severe disease, pregnancy, children or diagnostic uncertainty.

⚫ Uncomplicated P. falciparum Malaria

• ⏱️ Treat urgently; falciparum malaria can deteriorate rapidly.
• 💊 UK BNF first-line: artemether-lumefantrine for uncomplicated falciparum malaria.
• 💊 Alternatives may include atovaquone-proguanil or quinine-based regimens depending on circumstances and specialist advice.
• 🏥 Admit or observe according to severity, parasitaemia, comorbidity, pregnancy, ability to tolerate oral therapy and local policy.

🌿 Non-Falciparum Malaria

• Includes P. vivax, P. ovale, P. malariae and P. knowlesi.
• 💊 Chloroquine may be used for chloroquine-sensitive non-falciparum malaria.
• 💊 Use appropriate alternatives where chloroquine resistance is likely, e.g. artemether-lumefantrine or other specialist-recommended therapy.
• 🌙 Primaquine is used for radical cure of P. vivax and P. ovale hypnozoites. Check G6PD first and avoid in pregnancy.
• 🔴 Treat P. knowlesi carefully because it can progress rapidly; severe disease requires IV artesunate.

🚨 Severe Malaria

• 💉 IV artesunate is preferred for severe malaria.
• 🧴 If IV artesunate is not immediately available, use IV quinine according to specialist/local guidance while arranging artesunate.
• 🛠️ Supportive management: treat hypoglycaemia, seizures, shock, acidosis, severe anaemia, renal failure, ARDS and fluid/electrolyte disturbance.
• 🏥 Manage in a high-dependency/ICU setting if cerebral malaria, shock, respiratory failure, severe acidosis, renal failure, high parasitaemia or rapid deterioration.
• 🤰 Pregnancy requires urgent specialist obstetric, infectious diseases and anaesthetic input.

🛡️ Prevention

• 🛏️ Insecticide-treated bed nets, indoor residual spraying, mosquito-source control and prompt treatment reduce transmission.
• 👕🧴 Protective clothing, DEET-containing repellents and bite avoidance are important for travellers.
• 💊 Chemoprophylaxis for travellers should follow UKHSA/NaTHNaC destination-specific guidance.
• 💉 Vaccination: WHO recommends malaria vaccines RTS,S/AS01 and R21/Matrix-M for children in malaria-endemic areas as part of wider malaria-control programmes.

📌 Key Points

• ⏱️ Fever after travel to a malaria-endemic area is malaria until proven otherwise.
• 🔬 Diagnosis: urgent thick and thin blood films ± rapid diagnostic test; repeat films if suspicion remains.
• ⚫ P. falciparum is most likely to cause rapidly fatal disease.
• 🌙 P. vivax and P. ovale need radical cure with primaquine after G6PD testing.
• ⚠️ Drug resistance and pregnancy status change treatment choices — follow current BNF/local specialist guidance.

Cases - Malaria

• Case 1 - Severe falciparum malaria 🌍: A 27-year-old man returns from Nigeria with 3 days of fever, rigors and confusion. Exam: jaundice, splenomegaly, GCS 12/15. Bloods: Hb 8.5 g/dL, platelets 40 ×10⁹/L, creatinine 280 µmol/L. Blood film: P. falciparum parasitaemia 8%. Diagnosis: severe falciparum malaria. Managed with IV artesunate, ICU/HDU support, glucose monitoring and careful fluid balance.
• Case 2 - Relapsing malaria 🔄: A 32-year-old woman returns from India with intermittent fevers, sweats and malaise. Thick/thin films: P. vivax. Exam: splenomegaly and mild anaemia. Diagnosis: vivax malaria. Treat the acute episode according to resistance risk, then give primaquine for radical cure after confirming normal G6PD status.
• Case 3 - Imported uncomplicated malaria ✈️: A 19-year-old student presents with fever, myalgia and diarrhoea after a gap year in Ghana. She did not take prophylaxis. Blood film: ring forms of P. falciparum, parasitaemia 0.8%. Diagnosis: uncomplicated falciparum malaria. Managed with oral artemether-lumefantrine if clinically stable and able to tolerate oral therapy, with safety-netting and specialist/local protocol advice.

Teaching Point 🩺: P. falciparum causes most severe imported malaria and can rapidly lead to cerebral malaria, renal failure, ARDS, acidosis and shock. P. vivax / P. ovale relapse because of dormant liver hypnozoites, so acute treatment alone is not enough. P. malariae may cause quartan fever and chronic low-grade infection; rarely it is associated with nephrotic syndrome. Diagnosis relies on thick and thin blood films plus rapid antigen testing where useful. Management is species- and severity-specific, with IV artesunate for severe malaria and prevention through chemoprophylaxis, bite avoidance and public-health measures.