Agents, Transmission, Life Cycles, Drugs

Question 1

HAT

Answer 1

• Trypanosoma brucei
  
  • ​**gambiense - West African
  • rhodesiense - East African
• tsetse fly

Question 2

HAT/T. brucei

life cycle

Answer 2

1. bloodmeal, metacyclic trypomastigote into human
2. bloodstream trypomastigote - divide binary fission
3. short stumpy trypomastigote (stumpy induction factor, density-dependent) - don’t divide
4. blood meal, ingests bloodstream and short stumpy trypomastigote - bloodstream form dies
5. short stumpy forms procyclic trypomastigote - binary fission in insect midgut
6. into salivary gland, becomes epimastigote
7. epimastigote becomes proyclic trypomastigote

Question 3

HAT drugs

Answer 3

1. suramin
2. pentamidine
3. melarsoprol
4. eflornithine
5. NECT (nifurtimox-eflornithine combinatorial therapy)

Question 4

Major forms of HAT

(T. brucei)

Answer 4

1. metacyclic (infectious, insect → human, VSG)
2. bloodstream form (replicative, mammals, VSG)
3. short stumpy (infectous, human → insect)
4. procyclic (replicative, insects)
5. epimastigote (insect salivary gland)

Question 5

Chagas disease

Answer 5

• T. cruzi

transmission

• triatomine bugs
• zoonotic
  
  • sylvatic
  • peri-domicillary
  • domicillary
• ingestion of contaminated food/water, blood transfusion, organ transplant, congenital

Question 6

Chagas disease (T. cruzi)

major forms

Answer 6

epimastigote

• insesct midgut
• divides by binary fission
• non-infectious

trypomastigote

• can’t divide
• feces of insect
• highly infectious
  
  • metacyclic = insect to human
  • bloodstream form = humans to insect

amastigote

• intracellular
• divides by binary fission
• 500+ within mammalian cell
• infectious

Question 7

T. cruzi lifecycle

Answer 7

1. triatomine bug takes blood meal, metacyclic trypomastigote in through bite or mucus membranes
2. invades mammalian cells near bite (local tropism)
3. divide to amastigote (and zoid), which divide by binary fission and communicate to form (in sync)
4. bloodstream form trypomastigote burst into the bloodstream with tropism for tissues (cardiac, muscles, enteric nerves)
5. BSF taken up by insect, into midgut to form epimastigote
6. divide by binary fission
7. in hindgut form nondoviding metacyclic trypomastigote