American Trypanosomiasis Flashcards
T. cruzi
Chagas disease
T. cruzi and T. brucei have little in common
- epidemiologically different
- differences in transmission (both vectors but different vectors)
- pathogenesis
- clinical course
transmission of T. cruzi
- 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
Triatomine insects
- 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
T or F. T. c. enters a variety of host cells and multiplies in cytoplasm
T
T or F. Triatomine bugs are active in the day
F! Active at night
- typically live in the wall or roof cracks of poorly constructed homes in rural areas
what is an amastigote?
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
T. cruzi is characterized by two phases…
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
what happens if no successful therapy
8-12 acute symptoms and chronic phase lasts for life
inflammation lesion caused by T. c. at site of entry is called
chagoma
- if periocular tissue and painless edema = Romana sign
Romana sign
T. c. enters periocular site and painless edema appear
disease presentation of Chagas
fever, chills, anorexia, malaise, edema of face and lower extremities, lymphadenopathy and hepatosplenomegaly
** sometimes CNS involvement and acute myocarditis w arrhythmias
~ ___ to ___% will develop cardiac and/or GI forms of T.c. disease
20 to 30%
diagnosis of T. c.
- 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
congenital Chagas
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)