American Trypanosomiasis

Question 1

T. cruzi

Answer 1

Chagas disease

Question 2

T. cruzi and T. brucei have little in common

Answer 2

• epidemiologically different
• differences in transmission (both vectors but different vectors)
• pathogenesis
• clinical course

Question 3

transmission of T. cruzi

Answer 3

• triatomine insects or kissing bugs
• ingestion of food or drink contaminated with T.c. excreta (RARE)
• mother to child
• blood transfusion
• organ transplantation
• lab accidents

Question 4

Triatomine insects

Answer 4

• insect becomes infected by sucking blood from humans or other animals that have circulated trypomastigotes
• ingested parasites multiply in midgut of insects as epimastigotes => infective metacyclic trypomastigotes = discharged in feces
• transmission to humans occurs when mucus membranes, conjunctiva or breaks in the skin are contaminated w bug feces

Question 5

T or F. T. c. enters a variety of host cells and multiplies in cytoplasm

Answer 5

T

Question 6

T or F. Triatomine bugs are active in the day

Answer 6

F! Active at night
- typically live in the wall or roof cracks of poorly constructed homes in rural areas

Question 7

what is an amastigote?

Answer 7

protest cell that does not have visible external flagella or cilia
intracellular phase in life-cycle of trypanosomes that replicates
T.c. has this stage

Question 8

T. cruzi is characterized by two phases…

Answer 8

acute and chronic
- acute = 8 to 12 weeks after transmission
- chronic = host immune response decreases parasite replication so parasitemia falls below levels detectable by microscopy, acute symptoms resolve

Question 9

what happens if no successful therapy

Answer 9

8-12 acute symptoms and chronic phase lasts for life

Question 10

inflammation lesion caused by T. c. at site of entry is called

Answer 10

chagoma
- if periocular tissue and painless edema = Romana sign

Question 11

Romana sign

Answer 11

T. c. enters periocular site and painless edema appear

Question 12

disease presentation of Chagas

Answer 12

fever, chills, anorexia, malaise, edema of face and lower extremities, lymphadenopathy and hepatosplenomegaly

** sometimes CNS involvement and acute myocarditis w arrhythmias

Question 13

~ ___ to ___% will develop cardiac and/or GI forms of T.c. disease

Answer 13

20 to 30%

Question 14

diagnosis of T. c.

Answer 14

• serology (ELISA, IFA) = IgG!; chronic = low level parasitemia
• circulating parasites (motile); wet preps of anticoag blood, buffy coat
• tissue biopsies (amastigotes -> Giemsa, H&E)
• xenodiagnosis (OLD method; uninfected bug - let them eat from pt suspected w Chagas = then look for trypanosomes in GI of bug)
• PCR

Question 15

congenital Chagas

Answer 15

microscopic examination of cord blood or PCR or serology is not indicated as maternal Abs will be present in newborn
if microscopy and/or PCR negative = serology (IgG should be done 6-9 mos later)

Question 16

why do we have to do 2 serologic assays to diagnose T. c.

Answer 16

to rule out FP with
- malaria
- Leishmania
- syphilis
- some other parasitic and non-parasitic infections

Question 17

two first-line serological tetss for T.c.

Answer 17

EIA (enzyme immunoassay) on recombinant T. c. antigens and immunoblot (ESA)

• if discordant, IFA as tie-breaker

Question 18

T or F. There is no clinical evidence that antitryp therapy can reverse established Chagas cardiac disease

Answer 18

T! so prevention is key to avoid chronic Chagas cardiomyopathy (CCC)

Question 19

what is the focus for treatment on patients w advanced heart disease

Answer 19

supportive care for heart failure, arrhythmia, and thromboembolism

Question 20

T or F. Antitrypanosomal therapy has not been proven to affect progression of GI disease

Answer 20

T! management focuses on symptom amelioration

Question 21

T or F. Risk of Chagas disease to travelers is low

Answer 21

T!