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# Leishmania infantum

- Parasite
- Exam priority: high

A Leishmania that invades the liver, spleen and bone marrow. It causes fever, a huge spleen and anemia, mostly in young children; usually fatal untreated.

Updated 2026-11-01

Also called: Leishmania chagasi, kala-azar, visceral leishmaniasis

## Key points

- Prolonged fever, massive splenomegaly and pancytopenia in a child from the Caribbean region: think visceral leishmaniasis.
- Agent in the Americas: L. infantum (L. chagasi); main reservoir: the dog.
- Diagnosis: amastigotes in bone-marrow aspirate; rK39 rapid test.
- HIV coinfection: more disease, relapse and death.
- Liposomal amphotericin B as the preferred option in many guidelines.

## At a glance

**Shape**
Oval amastigote in tissue; promastigote in the vector

**Family**
Trypanosomatidae

**Type**
Intracellular flagellated protozoan (macrophages of the reticuloendothelial system)

**Stain**
Giemsa on bone-marrow or spleen aspirate

**Size**
Amastigote about 2 to 4 µm

## Morphology

- Amastigotes inside macrophages of bone marrow, spleen, liver and lymph nodes.
- Round nucleus and rod-shaped kinetoplast on Giemsa stain.
- Belongs to the L. donovani complex; L. chagasi is the older name used in the Americas.

## Transmission

- Bite of female Lutzomyia sand flies (in Colombia, mainly Lutzomyia evansi and Lutzomyia longipalpis).
- The dog is the main domestic reservoir.
- Rarely transfusion, shared needles or congenital.

**Reservoir:** Domestic dog (main); Opossums and foxes

**Vector:** Female sand flies of the genus Lutzomyia.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The sand fly bites and deposits promastigotes in the skin.
- Macrophages engulf them and they turn into amastigotes.
- Amastigotes travel through the reticuloendothelial system to the spleen, liver, bone marrow and lymph nodes.
- There they multiply and cause hepatosplenomegaly and marrow failure.
- The sand fly becomes infected by biting a dog or person with parasites in the skin or blood.
- In the insect it turns into a promastigote and migrates to the proboscis.

## Virulence factors

- Tropism for macrophages of the spleen, liver and bone marrow.
- Suppression of the Th1 response and interferon-gamma; malnutrition and HIV favor disease.
- Reticuloendothelial hyperplasia and polyclonal hypergammaglobulinemia; splenic sequestration of blood cells.

## Diseases it causes

- Visceral leishmaniasis (kala-azar): prolonged fever, splenomegaly, pancytopenia and wasting; fatal without treatment. [Leishmaniasis →](https://durgical.com/en/conditions/leishmaniasis/)

## Clinical picture

- Weeks of irregular fever, weight loss and a swollen abdomen.
- Marked splenomegaly and hepatomegaly.
- Pancytopenia: anemia, leukopenia and low platelets; bleeding and secondary bacterial infections.
- Most common in malnourished children under 5 and in people with HIV.

## Diagnosis

- Bone-marrow aspirate (or spleen aspirate in expert centers) with Giemsa: amastigotes in macrophages.
- Serologic tests, including the rK39 antigen rapid test.
- NNN culture and PCR to confirm and type.
- Pancytopenia and hypergammaglobulinemia as supporting clues.

## Treatment

Liposomal amphotericin B is the preferred treatment in many guidelines; alternatives are pentavalent antimonials, amphotericin B deoxycholate and miltefosine, depending on country and species. Malnutrition, anemia and associated infections also need management.

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

In Pharmacology:

- [Amphotericin B](https://durgical.com/en/pharmacology/amphotericin-b/)
- [Meglumine antimoniate](https://durgical.com/en/pharmacology/meglumine-antimoniate/)
- [Miltefosine](https://durgical.com/en/pharmacology/miltefosine/)

## Prevention

- Sand fly control in and around the home (spraying, clearing the surroundings).
- Surveillance of canine leishmaniasis and insecticide collars for dogs in endemic areas.
- Insecticide-treated nets and early diagnosis in children with prolonged fever.

**Vaccine:** There is no human vaccine.

## In Colombia

The visceral form is rare but very severe, with high case fatality. Active foci are in the Caribbean region, especially the Montes de María (Ovejas and Sincelejo in Sucre, El Carmen de Bolívar) and Córdoba, with historical foci also in the Magdalena valley (Tolima). It mostly affects young children in poor rural and peri-urban areas. New foci appeared in La Guajira and Córdoba in 2022.

## Memory aid

«The dog keeps it, the sand fly delivers it and the spleen balloons»: that is how kala-azar is built in the Montes de María.

## Test yourself

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

## Which species causes visceral leishmaniasis in Colombia?

Leishmania infantum (formerly called L. chagasi), of the L. donovani complex.

## What is the main domestic reservoir of L. infantum?

The dog, which can carry parasites in its skin and act as a source for sand flies.

## Which sample is used to see amastigotes in visceral disease?

Bone-marrow aspirate (or spleen aspirate in expert centers), stained with Giemsa.

## Which blood count findings suggest kala-azar?

Pancytopenia (anemia, leukopenia and thrombocytopenia), often with hypergammaglobulinemia.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/leishmania-infantum/)

## Related

- [Leishmania (Viannia) panamensis, L. braziliensis and L. guyanensis](https://durgical.com/en/microbiology/leishmania-panamensis-l-braziliensis-and-l-guyanensis/)
- [Plasmodium falciparum](https://durgical.com/en/microbiology/plasmodium-falciparum/)

## Related conditions

- [Leishmaniasis](https://durgical.com/en/conditions/leishmaniasis/)

## 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: Hemoflagellates (trypanosomes and Leishmania)](https://durgical.com/en/microbiology/groups/hemoflagellates/)

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

Sources: [CDC - DPDx - Leishmaniasis](https://www.cdc.gov/dpdx/leishmaniasis/index.html) (CDC, 2024); [Leishmaniasis](https://www.who.int/news-room/fact-sheets/detail/leishmaniasis) (WHO, 2023); [Informe de Evento 2023 Leishmaniasis](https://www.ins.gov.co/buscador-eventos/Informesdeevento/LEISHMANIASIS%20INFORME%20DE%20EVENTO%202023.pdf) (Instituto Nacional de Salud (INS) Colombia, 2024); [Clinical Care of Leishmaniasis | Leishmaniasis | CDC](https://www.cdc.gov/leishmaniasis/hcp/clinical-care/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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