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not to be confused with African trypanosomiasis which is caused by T. brucei gambiense and T. brucei rhodesiense and transmitted by Tse Tse flise


CHAGAS DISEASE

THE ORGANISM
infectious organism: T. cruzi, a flagellated protozoan
has a single nucleus and just one organelle, a kinetoplast-->one mitochondrion & DNA
reproduce asexually by binary fission
live one stage of their lives in the blood and/or tissues of vertebrate hosts
other stages in GI tracts of invertebrate vectors (temporary hosts)

forms: trypomastigote (tryps), amastigote, sluggish trypomastigote, and epimastigote
makes it adaptable to different/hostile environments
is a difficult and evasive target for attack by the immune system and immunization

METACYCLIC TRYPOMASTIGOTES
infectious form that goes from insect feces to burrow into skin
nucleus near posterior, free flagellum (tail) attached to an undulating membrane on the body
use flagellum to move through blood and attach to insect intestinal walls
tryps are 20 microns (0.20 mm) long and 3 microns wide
more than a million can fit in a pixel
travel through blood is brief
colonize muscle and neuron tissue-->encyst and form amastigotes

AMASTAGOTIC FORM
forms after entering muscle tissue, intracellular
round and oval in shape, without flagella
1.5-5 microns long
cluster together into cysts which can then erupt into blood stream to colonize new tissues
stumpy trypomastigotes mb ingested by vinchucas during bloodfeeding

EPIMASTIGOTIC FORM
vinchucas blood feed on infected animal/human
ingest stumpy trypomastigotes from chagas victims
vinchucas become carriers of T. cruzi for life, apparently unharmed
epimastigotes are formed in insects midgut, can survive there
flagellum attached near the center of the body
central nucleus and kinetoplast
multiply by binary fission
10 to 20 microns long-->grow another 10 microns as they travel to the insect's hindgut
turns to metacyclic trypamastigote in hindgut
insect stage takes 6-13 days



complicated and delicate relationship between T. cruzi and triatomines
T. cruzi has excellent defenses against human and animal immune systems
not to their advantage to destroy the host organism too quickly
-->low levels of parasitemia
rare to have a second acute phase

THE VECTOR
transmitted via triatomine bugs
(reduvid, kissing, assassin bugs in all Americas)
aka Triatoma infectans (vinchucas) are triatomine insects
houses mb infested with these insects
over 100 species that carry the parasite
subspecies Stercorian develops infectious stage while in insects GI tract
CDC pdf drawings: http://www.dpd.cdc.gov/dpdx/html/PDF_Files/Kissing_Bugs.pdf
photos: http://www.dpd.cdc.gov/dpdx/html/trypanosomiasisamerican.htm
(these are the bugs that Suzanne has been trained to hate and avoid! she grew up in AZ)

SOURCES
microbiology course notes
http://www.uta.edu/chagas/html/biolTcru.html
CDC: http://www.dpd.cdc.gov/dpdx/html/trypanosomiasisamerican.htm
JAMA review: http://jama.ama-assn.org/cgi/content/full/298/18/2171?ijkey=rYYxOg7FUukvI&keytype=ref&siteid=amajnls

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