Malaria is a life-threatening disease caused by protozoan parasites of the Plasmodium genus, transmitted to humans through the bite of infected female Anopheles mosquitoes.
Causative Agents
Five Plasmodium species cause malaria in humans:
- Plasmodium falciparum (most virulent; causes severe malaria)
- P. vivax (can cause relapsing malaria)
- P. ovale (relapsing, less common)
- P. malariae (associated with nephrotic syndrome)
- P. knowlesi (zoonotic, rapidly replicating)
Epidemiology
- Endemic in tropical and subtropical regions (Sub-Saharan Africa, South Asia, parts of Latin America).
- Children <5 years, pregnant women, immunocompromised individuals, and travelers to endemic areas are at highest risk.
- P. falciparum is predominant in Africa; P. vivax in Asia and Latin America.
Transmission
- By the bite of an infected female Anopheles mosquito during blood feeding.
- Transfusion, congenital, and needle-stick transmissions are rare but possible.
Life Cycle Summary
- Sporozoites inoculated by mosquito bite.
- Infect hepatocytes → asexual replication → merozoites.
- Merozoites infect RBCs → trophozoite and schizont formation.
- RBC lysis releases merozoites → febrile episodes.
- Some parasites form gametocytes (for mosquito transmission).
Clinical Presentation
Uncomplicated Malaria
- Non-specific symptoms: fever, chills, sweats, headache, nausea, vomiting, myalgia, arthralgia.
- Classical paroxysms (especially in P. vivax , P. ovale ): occur every 48-72 hours.
Severe (Complicated) Malaria — P. falciparum most common
Defined by the presence of any of the following:
- Cerebral malaria : seizures, coma, confusion.
- Severe anemia : Hb <5 g/dL.
- Hyperparasitemia : >5% or >200,000 parasites/µL (in high-transmission settings).
- Hypoglycemia (<2.2 mmol/L).
- Renal failure : oliguria, elevated creatinine.
- Pulmonary edema / ARDS .
- Shock, DIC, metabolic acidosis .
- Hemoglobinuria ("Coca-Cola urine").
Diagnosis
Outpatient
- Thick and thin peripheral blood smears : gold standard.
- Thick smear : sensitive for parasite detection.
- Thin smear : species identification and parasite quantification.
- Rapid Diagnostic Tests (RDTs) : useful if microscopy unavailable.
Inpatient / Severe Malaria
- Full blood count: anemia, thrombocytopenia.
- Blood glucose: detect hypoglycemia.
- Renal and liver function tests.
- Urinalysis.
- Repeat smears every 12–24 hours if initial test is negative but suspicion is high.
Treatment
Goals
- Eradicate parasites.
- Prevent complications and relapse.
- Interrupt transmission.
- Prevent drug resistance.
Uncomplicated Malaria
First-line (WHO-recommended):
- Artemisinin-based combination therapy (ACT)
- Artemether-lumefantrine (AL) : 6-dose regimen over 3 days (adult dose: 4 tablets at 0, 8, 24, 36, 48, 60 hrs).
Alternative regimens:
- Dihydroartemisinin-piperaquine
- Atovaquone-proguanil , Mefloquine , or Quinine + doxycycline/clindamycin in specific cases.
Treatment failure:
- Consider drug resistance or poor absorption.
- Use quinine 10 mg/kg q8h × 7 days.
Severe Malaria (Medical Emergency)
First-line agents:
- IV artesunate (preferred where available)
- OR IV quinine :
- Loading dose: 20 mg/kg in 5% dextrose over 4 hrs.
- Maintenance: 10 mg/kg q8h for 7–10 days.
- OR IM artemether :
- 3.2 mg/kg loading dose, then 1.6 mg/kg daily until oral therapy.
Supportive Care:
- Monitor vitals, glucose, urine output.
- Treat hypoglycemia: 50% dextrose 1 mL/kg IV bolus.
- Manage anemia: transfuse if Hb <5 g/dL + signs of cardiorespiratory compromise.
- Seizures: diazepam 0.3 mg/kg IV or rectal.
- Fluid resuscitation + furosemide if oliguria persists.
- Avoid overhydration to prevent pulmonary edema.
Transition to oral therapy (e.g., AL) once tolerated. Complete 7-day course.
Prevention and Chemoprophylaxis
Indications
- Non-immune travelers.
- Patients with SCD, thalassemia, HIV.
- Pregnant women (IPT with sulfadoxine-pyrimethamine).
- Children with impaired immunity or post-splenectomy.
Regimens
- Mefloquine : 250 mg weekly, start 2 weeks before travel, continue 4 weeks after return.
- Atovaquone-proguanil : daily, start 1–2 days before, continue 7 days post-travel.
- Doxycycline : daily, not for children <8 yrs or pregnant women.
Patient Education
- Always seek care for fever, especially after travel to malaria-endemic areas.
- Complete full course of prescribed anti-malarial medication.
- Use mosquito control methods (repellents, bed nets).
- Ensure chemoprophylaxis adherence if indicated.
High-Yield Pearls
- P. falciparum is the only species associated with cerebral malaria.
- Negative blood smear does not exclude malaria.
- Always consider malaria in febrile patients with recent travel to endemic areas.
- Hypoglycemia is a common complication, especially in children and during quinine therapy.
- Monitor parasite clearance with daily blood smears in severe cases.
