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

# Trypanosoma brucei gambiense and T. b. rhodesiense

- Parasite
- Exam priority: medium

An African parasite spread by the tsetse fly. It first causes fever and swollen glands, then invades the brain and disrupts sleep.

Updated 2026-11-01

Also called: sleeping sickness, human African trypanosomiasis

## Key points

- Vector: tsetse fly (Glossina); Africa only.
- VSG antigenic variation: waves of fever and no vaccine.
- Gambiense (West and Central Africa, chronic, Winterbottom's sign) versus rhodesiense (East, acute, chancre, cattle).
- CSF findings define the stage and change treatment.

## At a glance

**Shape**
Elongated trypomastigote with undulating membrane and free flagellum

**Family**
Trypanosomatidae

**Type**
Extracellular flagellated protozoan (blood, lymph and CSF)

**Stain**
Giemsa on thick and thin films; small kinetoplast

**Size**
Trypomastigote about 14 to 33 µm long

## Morphology

- Slender, wavy trypomastigote with a free flagellum and undulating membrane.
- Small kinetoplast, unlike the large one of T. cruzi.
- The two subspecies look identical under the microscope.

## Transmission

- Bite of the tsetse fly (Glossina), which feeds by day.
- Rarely congenital (gambiense), by transfusion or lab accident.

**Reservoir:** T. b. gambiense: mainly humans; T. b. rhodesiense: cattle and antelopes

**Vector:** Tsetse flies of the genus Glossina, found only in sub-Saharan Africa.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The tsetse fly injects metacyclic trypomastigotes into the skin.
- They enter lymph and blood, where they multiply extracellularly by binary fission.
- They invade other fluids and, in the second stage, reach the CSF and central nervous system.
- A fly takes up trypomastigotes when feeding; in its midgut they become procyclic forms and multiply.
- They turn into epimastigotes, reach the salivary glands and form new metacyclic forms in about 3 weeks.

## Virulence factors

- Antigenic variation of the variant surface glycoprotein (VSG): waves of parasitemia and antibody escape.
- Crossing the blood-brain barrier: meningoencephalitis and sleep disturbance.
- Immune activation with high IgM and inflammatory damage.

## Diseases it causes

- Human African trypanosomiasis: hemolymphatic stage (fever, lymphadenopathy) and meningoencephalitic stage (sleeping sickness). [Human African trypanosomiasis (sleeping sickness) →](https://durgical.com/en/conditions/human-african-trypanosomiasis/)

## Clinical picture

- Trypanosomal chancre at the bite site, more often with rhodesiense.
- Stage 1: intermittent fever, itching and lymphadenopathy; Winterbottom's sign (posterior cervical nodes) in gambiense.
- Stage 2: daytime sleepiness and night insomnia, behavior changes, motor disturbances and coma.
- Gambiense: chronic, months to years; rhodesiense: acute, weeks, with more cardiac involvement.

## Diagnosis

- Rapid serologic screening for gambiense (card agglutination test).
- Confirmation by seeing trypanosomes in blood (thick film, buffy coat), lymph-node aspirate or chancre fluid.
- Lumbar puncture for staging: trypanosomes or raised cell count in CSF mean stage 2.

## Treatment

Depends on subspecies and stage. Gambiense: oral fexinidazole, pentamidine in stage 1 and nifurtimox-eflornithine combination in stage 2. Rhodesiense: suramin in stage 1 and melarsoprol (highly toxic) in stage 2. None of this is acquired in the Americas.

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

In Pharmacology:

- [Pentamidine](https://durgical.com/en/pharmacology/pentamidine/)
- [Nifurtimox](https://durgical.com/en/pharmacology/nifurtimox/)

## Prevention

- Tsetse fly control with traps and insecticides.
- Active population screening in gambiense areas.
- Neutral-colored, long-sleeved clothing for travelers to rural Africa.

**Vaccine:** There is no vaccine; antigenic variation makes one hard to develop.

## In Colombia

There is no transmission in Colombia or the Americas. It matters for USMLE and for comparison with T. cruzi; any case in Colombia would be imported from Africa.

## Memory aid

«Tsetse puts you to bed»: the African fly ends up in the brain; the western form is slow, the eastern one fast.

## Test yourself

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

## What mechanism lets T. brucei escape antibodies?

Antigenic variation of its variant surface glycoprotein (VSG), which produces successive waves of parasitemia.

## What is Winterbottom's sign?

Posterior cervical lymphadenopathy, typical of the hemolymphatic stage of T. b. gambiense infection.

## Why is a lumbar puncture done in African trypanosomiasis?

To find out whether the nervous system is involved (stage 2), which changes the drug used.

## How does T. brucei differ from T. cruzi in the blood?

T. brucei multiplies extracellularly in blood; T. cruzi does not divide in blood and reproduces inside cells as an amastigote.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/trypanosoma-brucei-gambiense-and-t-b-rhodesiense/)

## Related

- [Trypanosoma cruzi](https://durgical.com/en/microbiology/trypanosoma-cruzi/)
- [Leishmania infantum](https://durgical.com/en/microbiology/leishmania-infantum/)

## Related conditions

- [Human African trypanosomiasis (sleeping sickness)](https://durgical.com/en/conditions/human-african-trypanosomiasis/)

## 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 - Trypanosomiasis, African](https://www.cdc.gov/dpdx/trypanosomiasisafrican/index.html) (CDC, 2024); [Trypanosomiasis, human African (sleeping sickness)](https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness)) (WHO, 2025).

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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/trypanosoma-brucei-gambiense-and-t-b-rhodesiense/