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Microbiology · Apicomplexans

Plasmodium falciparum !

  • Parasite
  • Exam priority: high

The deadliest malaria species. In Colombia it predominates on the Pacific coast and can cause cerebral malaria and organ failure.

Updated 2026-11-01

Also called: falciparum malaria, malignant tertian malaria

At a glance

Shape
Thin rings, often several per cell; crescent-shaped gametocyte
Family
Plasmodiidae
Type
Intracellular apicomplexan protozoan (liver and red blood cells)
Stain
Giemsa on thick and thin films: appliqué forms, Maurer's clefts
Size
Does not enlarge the red cell

Morphology

  • Delicate rings with one or two chromatin dots; forms pressed against the cell edge (appliqué).
  • Several parasites in one red cell; red cells of normal size.
  • Elongated crescent or sausage-shaped gametocytes, highly characteristic.
  • Mature trophozoites and schizonts are rarely seen in peripheral blood: they are stuck in capillaries.

Transmission

  • Bite of an infected female Anopheles.
  • Less often by transfusion, transplant, shared needles or congenitally.

Reservoir: Humans

Vector: Female Anopheles mosquitoes; on Colombia's Pacific coast An. albimanus is an important vector.

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Life cycle

  1. The mosquito bite deposits sporozoites that travel to the liver.
  2. In the liver it forms schizonts and releases merozoites; P. falciparum makes no hypnozoites.
  3. Merozoites invade red cells of any age, so parasitemia can be very high.
  4. Red cells with mature trophozoites stick to endothelium and are sequestered in the brain, placenta and other organs.
  5. Some parasites become gametocytes, which take several days to appear in the blood.
  6. A mosquito takes up gametocytes; the sexual phase happens inside it and sporozoites form in the salivary glands.

Virulence factors

  • PfEMP1 on red-cell knobs: adhesion to endothelium, sequestration and rosetting.
  • Invades red cells of all ages: high parasitemia and heavy hemolysis.
  • Sequestration in cerebral and placental microcirculation: cerebral malaria and fetal harm.
  • Intense inflammatory response (TNF and other cytokines), acidosis and multi-organ failure.
  • HRP2: the protein many RDTs detect; parasites with deleted genes can give false negatives.

Diseases it causes

  • P. falciparum malaria, uncomplicated or severe (cerebral malaria, severe anemia, kidney failure, pulmonary edema). Malaria →
  • Severe malaria with shock and multi-organ failure, which can behave like sepsis. Sepsis and septic shock →

Clinical picture

  • Irregular fever, chills, headache, malaise, vomiting; often with no clear rhythm.
  • Severe malaria: impaired consciousness or seizures, severe anemia, acidosis, hypoglycemia, shock, pulmonary edema or ARDS, kidney injury, bleeding, jaundice with another severity sign, or high parasitemia.
  • Pregnancy: higher risk of severe malaria, miscarriage, preterm birth and low birth weight.
  • It can go from mild to severe in less than a day in non-immune people.

Diagnosis

  • Giemsa thick film: confirms and counts parasitemia, key for judging severity and tracking response.
  • Thin film: fine rings, appliqué forms, multiple rings per cell and crescent gametocytes.
  • RDTs based on HRP2 or LDH; hrp2/hrp3 deletions have been reported in neighboring countries such as Peru and Brazil.
  • If the first film is negative and suspicion persists, smears are repeated every 12 to 24 hours.
  • Severity labs: hemoglobin, glucose, creatinine, bilirubin, lactate and blood gases.

Treatment

Uncomplicated malaria: artemisinin-based combination therapy (ACT, for example artemether plus lumefantrine); Colombia also gives a single primaquine dose to block gametocyte transmission. Severe malaria: intravenous artesunate followed by a full oral course. P. falciparum is chloroquine-resistant in Colombia; partial artemisinin resistance exists in East Africa.

Drug class only; doses and regimens are set by the clinician from the current guideline.

Prevention

  • Long-lasting insecticidal nets and indoor residual spraying.
  • Repellents and protective clothing at dusk; screens on doors and windows.
  • Diagnosis and treatment within 24 hours of fever onset.
  • Chemoprophylaxis for travelers to transmission areas, as medically indicated.

Vaccine: The RTS,S/AS01 and R21/Matrix-M vaccines target P. falciparum and are recommended by WHO for children in areas of moderate to high transmission in Africa. They are not part of Colombia's PAI.

Test yourself

Think of the answer, then tap the question to see it.

Why are schizonts rarely seen on a P. falciparum smear?

Because red cells with mature trophozoites and schizonts stick to endothelium via PfEMP1 and stay sequestered in capillaries.

Which gametocyte shape is typical of P. falciparum?

The elongated crescent or sausage-shaped gametocyte, longer than the red cell.

What is the treatment of choice for severe malaria?

Intravenous artesunate, followed by a full oral course of an artemisinin-based combination.

What limits HRP2-based rapid tests?

Some parasites carry hrp2/hrp3 gene deletions and do not make the protein, giving false negatives.

In which region of Colombia does P. falciparum predominate?

The Pacific region (Chocó, Nariño, Cauca and Buenaventura), where complicated malaria also concentrates.

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Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Malaria (CDC, 2024); Clinical Features of Malaria | Malaria | CDC (CDC, 2024); Clinical Testing and Diagnosis for Malaria | Malaria | CDC (CDC, 2024); INS hace un llamado a reforzar acciones territoriales para combatir la malaria (Instituto Nacional de Salud (INS) Colombia, 2025).

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Representative model, for educational purposes only.