Blood and Tissues – Trypanosoma cruzi
Topic Description
Morphology • Exists in three forms:
KS/K/C1/MK 1. Trypomastigote – Found in human blood; elongated,
spindle-shaped (15–20 µm); single nucleus at center; kinetoplast and
flagellum present forming undulating membrane.
2. Epimastigote – Found in vector (Reduviid bug); kinetoplast near
nucleus; short undulating membrane.
3. Amastigote – Intracellular, round/oval form (2–5 µm); found in
tissues (e.g., cardiac/smooth muscle).
Life Cycle • Definitive host: Human.
KS/K/C1/MK • Vector: Reduviid (kissing) bug (Triatoma).
1. Infected bug bites and deposits feces containing metacyclic
trypomastigotes near wound.
2. Parasites enter bloodstream through skin breaks.
3. Transform into amastigotes inside host cells (esp. cardiac/smooth
muscle).
4. Multiply and transform back into trypomastigotes, released into
blood.
5. Taken up by vector during blood meal → become epimastigotes in
midgut → multiply → infective metacyclic trypomastigotes in
hindgut.
Pathogenicity • Causes Chagas disease (American trypanosomiasis).
KS/KH/C2/MK • Amastigotes multiply intracellularly causing destruction of cardiac
and smooth muscle cells.
• Leads to myocarditis, cardiac dilation, and nerve ganglia destruction
(esp. in GI tract).
Clinical • Acute stage: Fever, malaise, lymphadenopathy,
Features hepatosplenomegaly, Romana’s sign (unilateral periorbital edema).
(Chagas • Chronic stage: Cardiomyopathy, arrhythmia, heart block,
Disease) megacolon, megaesophagus, neurological disorders.
KS/KH/C2/MK • May be asymptomatic for years before chronic complications appear.
Laboratory • Microscopy: Trypomastigotes in Giemsa-stained blood smears
Diagnosis (acute stage).
KS/K/C1/DK • Culture: NNN (Novy–MacNeal–Nicolle) or blood culture for
amastigotes.
• Serology: ELISA, IFAT for antibodies (chronic stage).
• Molecular: PCR for parasite DNA.
• Xenodiagnosis: Allowing uninfected bugs to feed, then examining
their gut for parasites.
Topic Description
Morphology • Exists in three forms:
KS/K/C1/MK 1. Trypomastigote – Found in human blood; elongated,
spindle-shaped (15–20 µm); single nucleus at center; kinetoplast and
flagellum present forming undulating membrane.
2. Epimastigote – Found in vector (Reduviid bug); kinetoplast near
nucleus; short undulating membrane.
3. Amastigote – Intracellular, round/oval form (2–5 µm); found in
tissues (e.g., cardiac/smooth muscle).
Life Cycle • Definitive host: Human.
KS/K/C1/MK • Vector: Reduviid (kissing) bug (Triatoma).
1. Infected bug bites and deposits feces containing metacyclic
trypomastigotes near wound.
2. Parasites enter bloodstream through skin breaks.
3. Transform into amastigotes inside host cells (esp. cardiac/smooth
muscle).
4. Multiply and transform back into trypomastigotes, released into
blood.
5. Taken up by vector during blood meal → become epimastigotes in
midgut → multiply → infective metacyclic trypomastigotes in
hindgut.
Pathogenicity • Causes Chagas disease (American trypanosomiasis).
KS/KH/C2/MK • Amastigotes multiply intracellularly causing destruction of cardiac
and smooth muscle cells.
• Leads to myocarditis, cardiac dilation, and nerve ganglia destruction
(esp. in GI tract).
Clinical • Acute stage: Fever, malaise, lymphadenopathy,
Features hepatosplenomegaly, Romana’s sign (unilateral periorbital edema).
(Chagas • Chronic stage: Cardiomyopathy, arrhythmia, heart block,
Disease) megacolon, megaesophagus, neurological disorders.
KS/KH/C2/MK • May be asymptomatic for years before chronic complications appear.
Laboratory • Microscopy: Trypomastigotes in Giemsa-stained blood smears
Diagnosis (acute stage).
KS/K/C1/DK • Culture: NNN (Novy–MacNeal–Nicolle) or blood culture for
amastigotes.
• Serology: ELISA, IFAT for antibodies (chronic stage).
• Molecular: PCR for parasite DNA.
• Xenodiagnosis: Allowing uninfected bugs to feed, then examining
their gut for parasites.
