Trypanosoma brucei

Question 1

How is T. brucei classified?

Answer 1

Extracellular protozoa hemoflagellate (flagellates in the blood)

Question 2

What species of T. brucei causes diseases?

Answer 2

T. brucei gambiense - chronic African Trypanosomiasis (98% of the cases)
- More dangerous than rhodensiense because the form is asymptomatic until it progresses to a more serious stage which is already to late to be treated

T. brucei rhodensiense - acute Afrtican trypanosomiasis (2% of the cases)
- much more acute and rapid than gambiense

Both are fetal if not treated

Question 3

How is T. brucei transmitted?

Answer 3

- bite by an infected tsetse fly 
  (Glossina species - both males and 
  females)
- mother to child infection 
- accidental infections in 
  laboratories/ blood transfusion/ 
  organ transplantation 
  transfusion 
- sexual contact

Question 4

What is the life cycle of T. brucei?

Answer 4

1. Tsetse fly takes a blood meal and injects metacyclic trypomastigotes in the skin tissue
2. These metacyclic trypomastigotes transform into blood trypomastigotes which are carried in other sited throughout the body reaching bodily fluids
3. Trypomastigotes multiply by binary fission in various body fluids (blood, lymph, and spinal fluid). They divide every 5-10 h extracellular for the long slender body. The shorty stumpy body does not divide and is more effective for tsetse flies.
4. Circulating trypomastigotes in blood during acute phase; usually undetectable in latent phase
5. Tsetse fly takes a blood meal and the bloodstream trypomastigotes are ingested
6. In the fly’s midguts the bloodstream trypomastigotes transform into procyclic trypomastigotes. These multiply by binary fission
7. Procyclic trypomastigotes leave the midgut and transform into epimastigotes
8. Epimastigotes multiply by binary fission in the salivary gland of the Tsetse fly. They transform into metacyclic trypomastigotes
9. The cycle starts over again (whole cycle takes 3 weeks)

Question 5

What is the infective stage of T. brucei?

Answer 5

Metacyclic trypomastigotes

Question 6

What type of life cycle does T. brucei have and what type of host does it have?

Answer 6

Indirect life cycle

Both humans and the tsetse fly are intermediated hosts

Question 7

What are the reservoirs of T. brucei besides humans?

Answer 7

domestic cattle (for rhodensiense), ungulates, primates

Question 8

What are symptoms of T. brucei?

Answer 8

Chronic infection (not self-limiting)
Infection occurs in 2 phases
First stage: Haemololymphatic stage
- parasite present in the blood circulation and symptoms occur 2-14 days after infection
- symptoms: chancre at site of inoculation, fever, headache, malaise, weakness and fatigue

Second stage: Meningoencephalitic stage

• parasite present in central nervous system
• symptoms: neuropsychiatric symptoms, reverse sleep/wake system, motor, and sensory symptoms
• without treatment the patient can go in a coma and have lethal outcome

Question 9

Where is T. brucei endemic?

Answer 9

Gambiense: West and Central Africa
Rhodensiense: East and Southeast Africa

Question 10

How is T. brucei diagnosed?

Answer 10

early diagnosis difficult because of non-specific symptoms and insensitive diagnostic measures (also can be mistaken for malaria (which may in fact occur as a co-infection))

Microscopy - identification of trypanosomes in a sample (chancre fluid, lymph nodes aspirates, blood, bone marrow, and during the neurological stage cerebrospinal fluid)

Serology: for gambiense (use for screening purposes)

Rapid diagnostic test

• for T gambiense
• passive screening and surveillance
• advantages: availability and easy

PCR - light microscopy

• uses blood and stage determination
• For both rhodesiense and gambiense
• disadvantage: invasive

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