DurgicalDurgical
EN
Open the app

Microbiology · Hemoflagellates (trypanosomes and Leishmania)

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

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

  1. The tsetse fly injects metacyclic trypomastigotes into the skin.
  2. They enter lymph and blood, where they multiply extracellularly by binary fission.
  3. They invade other fluids and, in the second stage, reach the CSF and central nervous system.
  4. A fly takes up trypomastigotes when feeding; in its midgut they become procyclic forms and multiply.
  5. 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

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:

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.

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)

← Back to the group: Hemoflagellates (trypanosomes and Leishmania)

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 (CDC, 2024); Trypanosomiasis, human African (sleeping sickness) (WHO, 2025).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.