[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Apicomplexans](https://durgical.com/en/microbiology/groups/apicomplexans/) › Plasmodium vivax

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# Plasmodium vivax

- Parasite
- Exam priority: high

The most common malaria parasite in Colombia. Spread by Anopheles mosquitoes, it can sleep in the liver and cause relapses months later.

Updated 2026-11-01

Also called: vivax malaria, benign tertian malaria

## Key points

- The most common species in Colombia and the Americas.
- Hypnozoites (also in P. ovale): relapses, hence primaquine or tafenoquine is added.
- Rule out G6PD deficiency before an 8-aminoquinoline (risk of hemolysis); not used in pregnancy.
- Enlarged red cell with Schüffner's dots; prefers reticulocytes.
- It can be severe: being vivax does not rule out complicated malaria.

## At a glance

**Shape**
Ring, amoeboid trophozoite, schizont and round gametocyte

**Family**
Plasmodiidae

**Type**
Intracellular apicomplexan protozoan (liver and red blood cells)

**Stain**
Giemsa on thick and thin films: Schüffner's dots

**Size**
Enlarges the red cell 1.5 to 2 times

## Morphology

- Enlarged, pale infected red cells with Schüffner's dots (pink stippling).
- Amoeboid, irregular trophozoite with fine yellow-brown pigment.
- Mature schizonts with many merozoites; round to oval gametocytes.
- All stages appear in peripheral blood, unlike P. falciparum.

## Transmission

- Bite of an infected female Anopheles, mostly at dusk and at night.
- Rarely by transfusion, transplant, shared needles or from mother to fetus.
- Not spread from person to person by contact.

**Reservoir:** Humans (a person with gametocytes in the blood)

**Vector:** Female Anopheles mosquitoes; in Colombia, species such as An. darlingi, An. albimanus and An. nuneztovari.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The mosquito injects sporozoites into the skin while feeding.
- Sporozoites reach the liver, multiply as schizonts and release merozoites.
- Some parasites stay dormant in hepatocytes as hypnozoites, which can wake months or years later.
- Merozoites invade reticulocytes and go through ring, trophozoite and schizont; synchronized rupture causes fever.
- Some become male and female gametocytes.
- A mosquito takes up gametocytes; in its gut a zygote, oocyst and new sporozoites form and move to the salivary glands.

## Virulence factors

- Duffy-binding protein: enters red cells through the Duffy antigen; Duffy-negative people are at lower risk.
- Preference for reticulocytes, which limits parasitemia.
- Liver hypnozoites: relapses without a new bite.
- Hemolysis and release of pigment and parasite products at each schizont rupture, which trigger cytokines and fever.

## Diseases it causes

- P. vivax malaria: usually uncomplicated, but it can be severe (anemia, thrombocytopenia, lung involvement, splenic rupture). [Malaria →](https://durgical.com/en/conditions/malaria/)

## Clinical picture

- Paroxysms of chills, high fever and sweating; the blood cycle lasts about 48 hours (tertian fever).
- Anemia, mild jaundice, splenomegaly and low platelets.
- Relapses weeks to years later if hypnozoites are not cleared.
- In pregnancy: maternal anemia and low birth weight.

## Diagnosis

- Giemsa-stained thick film: detects and counts parasites (the reference method in Colombia).
- Thin film: identifies the species by morphology (enlarged cells, Schüffner's dots).
- Rapid diagnostic tests (RDTs): useful where there is no microscopist; some detect only P. falciparum reliably.
- PCR to confirm species or mixed infections at reference labs.
- G6PD activity testing before primaquine or tafenoquine.

## Treatment

A blood schizonticide (chloroquine, where the parasite is still susceptible) plus an 8-aminoquinoline to clear hypnozoites (primaquine or tafenoquine) after G6PD testing. Chloroquine-resistant P. vivax has been reported in some parts of the world.

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

## Prevention

- Insecticide-treated bed nets, indoor residual spraying and removal of breeding sites.
- Repellents, covering clothes and window screens from dusk onward.
- Prompt diagnosis and treatment of every case to break transmission.
- Chemoprophylaxis for travelers on medical advice.

**Vaccine:** There is no vaccine against P. vivax. The RTS,S and R21 vaccines target P. falciparum and are not part of Colombia's PAI schedule.

## In Colombia

Malaria is a notifiable event (SIVIGILA, INS). P. vivax causes about two-thirds of cases and predominates in Urabá, Bajo Cauca, Alto Sinú, the Amazon and the Orinoquía. In 2024 the country had an outbreak with more than 135,000 cases; Chocó, Antioquia, Nariño, Córdoba and Vaupés account for most. The Voluntary Collaborators strategy diagnoses and treats in remote areas.

## Memory aid

Vivax «revisits»: it hides in the liver and comes back, so the cure needs a second key (primaquine) after a G6PD check.

## Test yourself

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

## Which P. vivax stage causes relapses?

The hypnozoite, a dormant liver-cell form that reactivates weeks or years later without a new bite.

## Which test is ordered before giving primaquine?

G6PD enzyme activity, because primaquine can cause severe hemolysis in people with the deficiency.

## Which thin-film finding points to P. vivax?

Enlarged, pale red cells with Schüffner's dots and amoeboid trophozoites.

## Which red-cell antigen does P. vivax use to get in?

The Duffy antigen; Duffy-negative people are therefore at lower risk of infection.

## What is the reference method for diagnosing malaria in Colombia?

The Giemsa-stained thick film, which detects and counts parasites; the thin film helps define the species.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/plasmodium-vivax/)

## Related

- [Plasmodium falciparum](https://durgical.com/en/microbiology/plasmodium-falciparum/)
- [Plasmodium malariae and Plasmodium ovale](https://durgical.com/en/microbiology/plasmodium-malariae-and-plasmodium-ovale/)
- [Babesia spp.](https://durgical.com/en/microbiology/babesia-spp/)

## Related conditions

- [Malaria](https://durgical.com/en/conditions/malaria/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Apicomplexans](https://durgical.com/en/microbiology/groups/apicomplexans/)

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](https://www.cdc.gov/dpdx/malaria/index.html) (CDC, 2024); [Malaria](https://www.who.int/news-room/fact-sheets/detail/malaria) (WHO, 2025); [Clinical Features of Malaria | Malaria | CDC](https://www.cdc.gov/malaria/hcp/clinical-features/index.html) (CDC, 2024); [INS hace un llamado a reforzar acciones territoriales para combatir la malaria](https://www.ins.gov.co/Noticias/Paginas/INS-hace-un-llamado-a-reforzar-acciones-territoriales-para-combatir-la-malaria.aspx) (Instituto Nacional de Salud (INS) Colombia, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/plasmodium-vivax/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/plasmodium-vivax/