This document summarizes information about Trypanosoma brucei, the parasite that causes Human African Trypanosomiasis (HAT) or sleeping sickness. It describes the parasite's morphology, life cycle, subspecies that infect humans, vector, geographical distribution, stages of infection, pathogenesis, diagnosis, treatment, and epidemiology. HAT affects around 36 countries in sub-Saharan Africa and causes approximately 40,000 deaths per year, though reported cases have decreased significantly in recent decades.

1. Bio 51
Parasitology
Trypanosoma brucei
Prepared by:
NOE P. MENDEZ
CENTRAL MINDANAO UNIVERSITY (CMU)
npolomendez@gmail.com

2. References
• Neva, F. A. & Brown, H. W. 1994. Basic clinical parasitology.
6th Ed. Appilton & Lange Paramount Publishing Business
and Professional Group: USA.
• Steverding, D. 2008. The history of African trypanosomiasis.
Biomed Central. Accessed on Dec. 1, 2015 at http://www.
parasitesandvectors.com/content/pdf /1756-3305-1-3.pdf
• Trypanosomiasis. World Health Organization. Accessed on
Dec. 1, 2015 at http://www.who.int/ mediacentre/factsheets/
fs259/en/
• Parasites – African trypanosomiasis. CDC. Accessed on Dec.
1, 2015 at http://www.cdc.gov/parasites/sleepingsickness/
biology.html

3. Scientific Classification
• Domain: Eukarya
• Kindom: Protista
• Phylum: Sarcomastigphora
• Class: Zoomastogophorea
• Order: Kinetoplastida
• Family: Trypanosomatidae
• Genus: Trypanosoma
• Species: T. brucei
• Sub-species: T. b. brucei, T. b. gambiense, T. b. rhodesiense

4. Trypanosoma brucei Morphology

5. Trypanosoma brucei
• micrograph under SEM:

6. Trypanosoma brucei
• stained under bright-field microscope:

7. Trypanosoma brucei
• T. brucei causes Human African Trypanosomiasis
(HAT) or sleeping sickness
• T. brucei is not killed by the immune system
because it has a glycoprotein (VSG) coating.

8. Trypanosoma brucei subspecies
• Two subspecies that are morphologically
indistinguishable cause distinct disease patterns
in humans:
1) T. b. gambiense causes West African
trypanosomiasis
2) T. b. rhodesiense causes East African
trypanosomiasis
• A third member, T. b. brucei, under normal
conditions does not infect humans.

9. Vector of T. brucei
• Tsetse fly belongs to the genus Glossina

10. Geographical Distribution of African
Trypanosomiasis
G.palpalis G.morsitans
In West Africa In East Africa

12. T. brucei Life Cycle

13. Stages of Infection
• In the first stage, the trypanosomes multiply in
subcutaneous tissues, blood and lymph. This is
also called haemo-lymphatic stage.
• In the second stage, the parasites cross the
blood-brain barrier to infect the central nervous
system. This is known as the neurological or
meningo-encephalic stage.

14. Pathogenesis
• Incubation period: 2 weeks
• Trypanosomal chancre will develop at the site of
bite
• Via lymphatics: enlarged lymph nodes especially
posterior cervical region (Winterbottom’s sign)
• Via blood stream: headache, fever, muscle &
joint pain, irregular erythematous rash

15. Pathogenesis
• Invasion of bone marrow (hypoplastic anemia)
• Enlarged liver & spleen
• Invasion of the CNS: severe headache, mental
apathy, slow speech, deep sleep, coma & death

16. Winterbottom signTrypanosoma chancre
Coma before death

17. Diagnosis
Disease management is made in 3 steps:
• Screening for potential infection
- involves using serological tests and checking
for clinical signs
• Diagnosing by establishing whether the parasite is
present in body fluids.
• Staging to determine the state of disease
progression.
- entails examining the cerebrospinal fluid
obtained by lumbar puncture.

18. Treatment (according to WHO)
• First stage treatment:
- Pentamidine
- Suramin
• Second stage treatment:
- Melarsoprol
- Eflornithine
- combination treatment of Nifurtimox and
Eflornithine

19. Epidemiology (WHO)
• HAT affects 36 countries in sub-Saharan Africa
• According to the World Health Organization,
HAT causes ~40,000 deaths in Africa annually.
• Cases involving T. b. rhodesiense are much rarer
than those involving T. b. gambiense.

20. Epidemiology (Steverding, 2008)
• The total amount of reported HAT cases has
decreased substantially over time.
• 1998: ~40,000 reported cases; >250,000
actual cases
• 2004: ~18,000 reported cases; between
50,000 and 70,000 actual cases
• 2010: ~7,000 reported cases; ~30,000 actual
cases

21. End of Report