BLOOD, BONE MARROW, SPLEEN
AND HEART AND MUSCLES PARASITES
ZOOMASTIGOPHOREA Order: Kinetoplastida

TRYPANOSOMA CRUZI (Chagas' disease)

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 T. cruzi: american trypanosomiasis was first
described by Carlos Chagas in Brasil in 1909.
The infection, Chagas' disease, is caused
by the haemoflagellate Trypanosoma cruzi.
tc1: T.cruzi in blood sample, Giemsa.

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T. cruzi: the disease is a public health threat in most Latin American countries,
although cases due to blood derivatives or blood transfusion
has been reported in non-endemic regions.
According to WHO the overall prevalence of human T.cruzi infection
is estimated in 18 million cases and 100 million people are living at risk.
tc2: T. cruzi: geographical distribution.

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T. cruzi: the vectors are reduvidae bugs which are haematophagus
and the most important are Triatoma infestans
(Argentina, Chile, Brazil, Bolivia, Paraguay, Uruguay, Peru),
T. sordida (Argentina, Bolivia, Brazil, Paraguay),
Rhodnius prolixus (Colombia, Venezuela, Mexico, Central America),
T. dimidiata (Ecuador, Mexico, Central America),
and Panstrogylus megistus (northeast Brazil).
tc3: Adult specimens of T.infestans and Rhodnius prolixus,
both important vectors of Chagas’ disease.

tc3b: Triatoma infestans 

tc3c: Rhodnius prolixus

tc4: T.dimidiata

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T. cruzi: the transmission by the vector is faecal.
T.cruzi infective metacyclic trypomastigotes are shed
in the faeces of the bug and are inoculated into
the human host by scratching infected faeces into skin abrasions
usually caused by the bug in the process of feeding (blood-sucking).
tc5: T.cruzi metacyclic trypomastigote: scanning electron microscopy
showing T.cruzi trypomastigotes recovered from an infected
Triatoma spp. in Pedro Carbo, Ecuador.

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T. cruzi: infective metacyclic trypomastigotes are shed in the faeces
of the bug and inoculated into the vertebrate host not only
by skin lesions but also through the mucosa of the mouth and,
in humans, through the conjunctiva of the eyes.
tc6: Life cycle

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T. cruzi: trypomastigotes can infect most of the vertebrate cells,
polymorphonuclear leucocytes and macrophages are probably among
the first vertebrate host cells with which T.cruzi interacts in vivo.
tc7a: In vitro T.cruzi infection of macrophages showing the presence of amastigotes:
Wright-Giemsa stain, showing replicating T.cruzi amastigotes within host cell.

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T. cruzi: this invasive step is crucial for the life cycle of the parasite
since it has to become intracellular to multiply.
tc7b: In vitro T.cruzi infection of macrophages showing the presence of amastigotes:
immunofluorescence assay showing T.cruzi amastigotes after treatment
with anti-T.cruzi polyclonal mouse sera.

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T. cruzi: trypomastigotes in the host cell transform into amastigotes,
which multiply intracellularly by binary division inducing inflammatory
and immunological responses in vivo, and destroy cells in vitro.
Amastigotes are then released into the blood stream as trypomastigotes.
The latter are nondividing forms which are able to infect a wide range
of new host cells but muscle and glia seem most often parasitized,
or they have to be ingested by another reduviid bug
in order to continue the parasite life cycle in the invertebrate host.
tc8: Trypomastigotes reach the myocardial cells and after penetration
they multiply as amastigotes with formation of a pseudocyst.

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T. cruzi: in the Reduvidae bug the bloodstream derived trypomastigote
forms pass along the digestive tract through irreversible
morphological transformations in sequence;
each developmental stage occurs in a specific portion of the insect's gut.
Thus, in the stomach, most blood trypomastigotes change into
epimastigotes and rounded forms (sphaeromastigotes).
tc9: T.cruzi epimastigote. Immunofluorescence studies using
antibodies to a T.cruzi protein named Tc52
(immunosuppressive factor which also express a thiol-transferase activity)
and confocal microscopy.
An intense labeling located at the posterior end of
an epimastigote indicate that Tc52 is targeted to the reservosomes
(These organelles are small vesicles inside multivesicular structures
being formed predominantly at the posterior end of epimastigotes).

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T. cruzi: epimastigotes divide actively in the vector's intestine and reach
the rectum where a final differentiation results in the infective metacyclic
trypomastigotes which are eliminated in the bug's faeces.

tc10: T.cruzi epimastigote. Epimastigote reacting with
a monoclonal antibody against T.cruzi.

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 T. cruzi: some researchers have postulated that sphaeromastigotes
may change either into short epimastigotes,
dividing forms in the intestine, or into long epimastigotes
which are nondividing forms but are able to reach the rectum
where they transform into the final metacyclic trypomastigote form.
In any case, this hypothesis remains controversial.
tc10b: T.cruzi epimastigote. Scanning electron microscopy
showing T.cruzi epimastigote.

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T. cruzi: there are three phases of the infection.
The acute phase usually passes unnoticed but
there may be an inflamed swelling or chagoma
at the site of entry of the trypanosomes.
Romanas'sign is when this swelling involves the eyelids
but it occurs only in about 1-2% of the cases.
In the acute phase, mortality is less than 5% and
death may result from acute heart failure
or meningoencephalitis in children less than two years old.
tc11: Romana’s sign, clinical manifestation tipically observed
in the acute phase of some Chagas’ disease patients.

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T. cruzi: general symptoms in acute Chagas' disease
may also include fever, hepatosplenomegaly, adenopathies and myocarditis.
Electrocardiographic changes involve sinus tachycardia, prolongation
of the P-R interval, primary T-wave changes and low QRS voltage.
Chest X-ray can reveal cardiomegaly of different degrees.
The intermediate phase is clinically asymptomatic
and is detected by the presence of specific antibodies.
No parasites are found in bloostream smears but
xenodiagnosis could be positive in some cases. 
Acute Chagas myocarditis (Haematoxylin and Eosin X 160)

tc12: Posteroanterior chest radiograph showing enlarged
heart due to T.cruzi infection. 

tc12a: Acute Chagas' disease myocarditis 
(Haematoxylin and Eosin X160)

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T. cruzi: the chronic phase of Chagas'disease develops 10 - 20 years
after infection and affects internal organs such as the heart,
oesophagus and colon as well as the peripheral nervous system.
The lesions of Chagas’ disease are incurable and in severe cases
patients may die as result of heart failure.
tc13: T.cruzi parasitize mainly the cardiac muscle but any cell type
may be parasitized (smooth muscle cells, hystiocytes):
cardiac muscle with amastigotes, H&E stain. 

tc13a: Chagas' disease megacardia 
(slide from the late Prof.Koberle, Brazil) 

tc13a: Apical aneurysm in Chagas' disease 
(slide from the late Prof.Koberle, Brazil)

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T. cruzi: on the other side, megacolon is associated
with abnormal constipation (weeks).
Faecal impaction and sigmoid volvulus are side-effects of megacolon.
Neurological changes in chronic Chagas' disease include changes
at the level of the central, peripheral or autonomic nervous system.
tc14: Chagasic megacolon with enlargement of the sigmoid;
patient from Morona Santiago province, southeastern Ecuador *

tc14a: X-ray showing megaoesophagus in Chagas' disease, Brazil 

tc14b: X-ray showing megacolon in Chagas' disease, Brazil

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            tc15: T. cruzi: can be observed in the peripheral blood
only in the acute case of the disease.
Its presence is the best definition of the acute phase
as all other signs are variable.
  tc15: Wright-Giemsa staining of T.cruzi trypomastigote 
in peripheral blood smear from an acute infected patient. 

  tc15b: T.cruzi in mouse blood (Giemsa stain)

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T. cruzi: trypomastigotes have a prominent subterminal kinetoplast
that often distort the membrane of the cell,
an elongated nucleus and an undulating membrane.
tc16: T.cruzi trypomastigote: blood stream trypomastigotes are 15-20 µm
in lenght and appear with a typical C or S-shaped form.

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T. cruzi: multiplication only occurs in the amastigote phase,
which grows in a variety of tissue cells especially muscle.
tc17: In vitro infected fibroblast showing a large number
of intracellular amastigotes.

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T. cruzi: laboratory diagnostic tests based on serology (IFA, ELISA)
and Polymerase Chain Reaction (PCR) specific for T.cruzi, have been developed.
tc18: T.cruzi trypomastigotes reacting with monoclonal Ab.

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T. cruzi: serological cross-reactions can occur with infections
such as leprosy, leishmaniasis, treponematoses, malaria and multiple myeloma.
Trypanosoma rangeli is also an important cause of false-positive testing,
especially in areas where T.cruzi coexists with T.rangeli.
tc19: In vitro T.cruzi infection of macrophages
showing the presence of amastigotes:
confocal microscopy showing T.cruzi amastigotes
after treatment with anti-Tc24 mouse sera.

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T. cruzi: two drugs are in common use.
Nifurtimox (Lampit, production was discontinued in 1991)
and Benznidazole (Rochagan).
The latter which is now the drug of choice,
is given in an oral dose of 6 mg/kg body weight for 30 or 60 days.
Both drugs produce anorexia, weight loss, headache and dizziness,
gastric irritation, and sometimes peripheral neuritis.
Experimental drugs are under evaluation.
Treatment of patients in the intermediate or chronic phase is controversial.
Congenital Chagas'disease and transfusion-associated
acute disease require Rochagan therapy.
Transfusion infection can be prevented by donor screening or,
by mixing the blood with gentian violet (0,25 gr./L for 24 hours) to kill T.cruzi.
Vector control programmes involving insecticide spraying
with modern pyretroids and new tools for delivery in endemic
areas is being carried out in some Latin American countries.
tc20: TEM microphotograph of T.cruzi epimastigote.

BLOOD....HEART....