Trypanosomes

Question 1

Two species of Trypanosomes we need to know:

Answer 1

1. T. cruzi

2. T. brucei

Question 2

Let’s start with T. cruzi. Where do we find this guy?

Answer 2

South/Central America

This is also called: American Trypanosomiasis

Question 3

Will T. cruzi be in the clean homes or the dirty ones?

Answer 3

Dirty ones. It’s a/w with rural, poor housing w/ dirt walls

Question 4

What 3 considerations should you make with dx of T. cruzi

Answer 4

1. Blood smear shows trypanosoms during active infection
2. Use serology during chronic infection
3. Cardiac biopsy shows trypanosoms in myocytes. (not often done)

Question 5

What signs will you see in an acute (w/in 1-2 wks) infection of T. cruzi?

Answer 5

1. Romana’s sign (feces drips into your eye→ painless unilateral periorbital edema).
2. Chagoma: indurated lesion at site of parasite entry
3. Rarely causes acute myocarditis or meningoencephalitis mostly in infants and immunocompromised pts.

Question 6

Will the smear be + in an acute T. cruzi infection?

Answer 6

Yes, as will culture and PCR

Question 7

In the chronic form of the disease (4-8 wks post infection) will the smear still be +?

Answer 7

Nope, dx is done by serology (*2 different assays w/ 2 different antigens)

Question 8

What’s going on in the intermediate form of T. cruzi?

Answer 8

2 options here:

1. No sx (70-80% of pts)
2. Develop Chagas dz (20-30% of pts)

Question 9

What are we going to see in Chagas Disease?

Answer 9

1. Dilated cardiomyopathy (often fatal). R-bundle branch block. Other structural/conduction heart problems. (80% of pts)
2. Mega-esophagus
3. Megacolon: constipation, acute abdomen w/ perforation of colon

Question 10

Tell me the 3 forms of T. cruzi?

Answer 10

Vector form: Epimastigote, metacyclic tryp.
Blood form: trypomastigote, classically “C” shaped.
Tissue form: amastigote.

Question 11

What’s the vector for T. cruzi?

Answer 11

1. Reduviid in the Family Triatomine aka “Kissing bug” (big bug bites in the night).
2. American vectors include raccoons, armadillos, skunks.

Other silly ways to get it: juices in endemic areas, contaminated blood donation.

Question 12

What’s the pathophys of T. cruzi

Answer 12

Feces deposited when bug bites around human’s mouth, typically. Goes into skin by itching. Tissue form, amastigote, tunnels into tissue and feeds on blood/lymph.

Question 13

Is this guy, T. cruzi, motile? Discuss.

Answer 13

Yes, it’s motile with base of flagella in close association with the kinetoplast. Kinetoplast contains DNA (similar to mitochondrial DNA in that it’s minicircles)

Question 14

What’s the treatment for T. Cruzi?

Answer 14

Acute: Nifurtimox
Benznidazole.
No tx for chronic Chagas.

Question 15

Moving on to T. brucei. Where does this dude live?

Answer 15

AFRICA.

Question 16

There are two kinds of T. brucei. They are:

Answer 16

1. Gambiense
2. Rhodesiense

(western vs eastern part of Africa respectively).

Question 17

What type of infection will travelers get? Gambiense or Rhodesiense?

Answer 17

Travelers get Rhodesience > Gambiense (people get it on safaris–it has much higher parasitemia and can present as acute febrile illness)

Question 18

How does the dx work for T. brucei?

Answer 18

Trypomastigotes seen on blood smear. CSF (LP) or lymph also used sometimes.

Question 19

What’s the main thing we’re worried about with T. brucei?

Answer 19

African Sleeping Sickness (Human African Trypanosomiasis aka HAT)

1. Acute phase: may see chancre
2. Recurrent fevers (blood infection)
3. Cervical/axillary lymphadenopathy→ Winterbottom’s sign=posterior cervical adenopathy
4. Personality changes, ataxia, tremor, daytime somnolence, insomnia, coma (CNS infection)

Question 20

What’s a special cell you might see with a T. brucei infection?

Answer 20

Mott cells: large eosinophilic plasma cells that failed to release its IgM (has a ton of IgM in it)

Question 21

Different forms of T. brucei?

Answer 21

1. Vector form: epimastigote, metacyclic tryp,
2. Blood form: Trypomastigote.
3. No tissue form: Stays extracellular.

Question 22

Vector for T. brucei?

Answer 22

Tsetse fly.

Question 23

Tell me two things about the structure of T. brucei?

Answer 23

1. Has variable surface glycoprotein (VSG) coats that undergo constant antigenic variation → chronic infection.
2. Motile, w/ single flagella.

Question 24

Tx for Gambiense?

Answer 24

Early gambiense: pentamidine

Late gambiense: eflornithine/nifurtimox

Question 25

Tx for Rhodesiense?

Answer 25

Early: suramin (for blood infection, can’t cross BBB) Late rhodesiense: melarsoprol (for CNS infection, can cross BBB, arsenical aka super toxic, side effect = hemorrhagic encephalopathy)