Trypanosoma cruzi and Chagas disease

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Trypanosoma cruzi and Chagas disease
Medical Parasitology, CBIO 4500/6500 Spring
2008 Silvia N.J. Moreno
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Kinetoplastids

• Flagellated protozoa
• They have an organelle named the Kinetoplast, a
  DNA-containing compartment located within the
  single mitochondrion and associated with the
  flagellar base.

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The Kinetoplastids

• Two medically important groups
• Leishmania spp. (leishmaniasis)
• Trypanosomes Trypanosoma spp.
• (African trypanosomiasis, "sleeping sickness")
• Trypanosoma cruzi (American trypanosomiasis,
  Chagas' disease)

Trypanosome are hemoflagellates- they live in the
circulatory system and tissue fluids some invade
cells. Most trypanosome spp. are transmitted by
blood-sucking arthropods
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TRANSMISSION-VECTORS

• TWO TYPES OF VECTORS

Biological vectors parasites undergo
developmental changes in the vector. The
leishmania parasites are transmitted by the bite
of the sandfly
Transport vectors parasite can survive long
enough to be transmitted by direct contact or
insect bite (T. evansi and T. equiperdum)
Example of a transport vector
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Trypanosomes are classified according to how they
are transmitted

• Two groups
• Stercorarian parasites develop in the posterior
  part of the vector and are transmitted through
  release of parasites with feces during feeding.
  (T. cruzi)
• Salivarian parasites develop in the anterior
  part of the insect vector and are transmitted by
  injection with saliva during feeding (African
  trypanosomes)

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Trypanosome forms
Anterior

• They change body forms during their life cycle
• Trypomastigotes 15-80 ?m single flagellum
  posterior to the nucleus. Found in the mammalian
  host in the blood. Also as metacyclics in the
  insect vector. Undulating membrane.
• Epimastigote flagellum anterior to the nucleus.
  Present in the insect vector
• Amastigotes short or no flagellum.
  Intracellular form in mammalian cells

Posterior
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American trypanosomiasis Chagas disease

• It was first described in 1909 by the Brazilian
  physician Carlos Chagas.
• He was working in Lassance, a railroad-worker
  town at the end of the new railroad line across
  Brazil, where immigrant railroad workers were
  dying from what was thought to be malaria. Chagas
  set up a lab and found that some symptoms were
  not from malaria and he found flagellated
  protozoa in the hindgut of the barbeiro which
  sucked blood from the workers at night. These
  protozoa were similar to the ones causing African
  sleeping sickness. Subsequent research proved the
  infection cycle of the trypanosome, later named
  T. cruzi (after Chagas' mentor), was directly
  related to poverty, such as that existed in
  Lassance.
• He was twice nominated for the Nobel Prize but
  the brazilian medical community did not support
  it since they did not believe in his discovery.

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CARLOS CHAGAS
The people in Lassance complained about about
irregular heartbeats and atypical arrhythmias,
indicating cardiac insufficiencies, frequently
leading to sudden death! Chagas linked the
endemicity of myocardial failure and the
triatomine bug. Called barbieros or barber
bugs because of their predilection for drawing
human blood, these large black insects were
unknown in the Brazilian coast. But the workers
in the interior knew them well, and described to
Chagas their nocturnal encounters with the
creatures that would emerge from cracks in the
walls to feed upon their blood. Patients
sometimes developed swollen bite sites near the
eyelids and lips, and for this reason they called
the insects kissing bugs. Chagas dissected
insects and inspected their gut flora with a
simple light microscope.
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SALVADOR MAZZA
He was born in Argentina in 1886. He met Chagas
in 1918 and his interest in the disease was
stimulated. He directed an organization MEPRA
which was dedicated in 1928. Under his direction,
MEPRA took an important role in the understanding
of the pathology of Chagas disease. The disputed
results of Carlos Chagas were confirmed by Mazza
and the disease was finally accepted by the
medical community. Mazza re-described the
parasite and the disease which finally convinced
the skeptical medical community. The disease is
also called Chagas-Mazza.
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The disease is endemic in Latin America, most
frequently in Argentina, Bolivia, Brazil, Chile,
Uruguay, and Venezuela.
20 million infected 40 million at risk gt50,000
deaths per year
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Emerging Infectious Diseases, 2003. 9103
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Trypanosoma cruzi transmission

Maternal transmission
It is transmitted naturally through the bite of a
reduviid bug which defecates during feeding and
parasites are eliminated with the feces
Blood transfusion is an important transmission
route in non-endemic zones
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Alternative routes of transmission blood
transfusion mother to child transplantation acc
idental lab inoculations
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Trypanosoma cruzi life cycle
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Two common vector species (reduviid)
Rhodnius prolixus sylvatic areas
Triatoma infestans urban areas
Adult, dorsal
Anterior end, dorsal view.   The head is long.
The clypeus at the front of the head is narrow at
the top and the genae (lateral sides of the head)
diverge toward the front of the head. The base of
the antenna is at the middle
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T. cruzi cycle in the mammalian host
Metacyclic trypomastigotes in bug feces deposited
on skin
Bloodstream trypomastigotes. Do not multiply but
infect other cells and transform into amastigotes
Trypomastigote transforms into amastigotes inside
the host cell which multiplies by binary fision.
Cell becomes full of parasites (pseudocyst)
ruptures and releases trypomastigotes into the
blood.
Rubbed into bite puncture abrasion or conjuntiva
Trypomastigotes enter host cell. Close to the
site of infection.
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Parasite development in the reduviid bug
(vinchuca)
Transform to epimastigotes which divide by
binary. Epimastigotes are also grown in culture
in suspension.
Mature in the posterior end of the bug and
transform to small metacyclic trypomastigotes
Trypomastigotes in the blood are ingested by bug
Epimastigotes are adapted to survive the insect's
intestines. They have flagellum anterior to the
nuclei, which differ from tryps whose flagellum
starts posterior to the nuclei. Epimastigotes
have a central nucleus and kinetoplast. They
multiply by binary fission. Epimastigotes are
10-20 microns long but grow another 10 microns as
they travel to the insect's hindgut, where they
transform into metacyclic trypomastigotes. No
apparent damage to the vinchuca is seen.
Epimastigotes can be cultured axenically.
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Mammalian forms of T. cruzi
The amastigote the intracellular form, round,
flagellum not visible, low motility. Divides by
binary fission. Amastigotes are intracellular,
round and oval in shape, and without flagella.
They are 1.5 to 5 microns long. Amastigotes
cluster into cysts and the cell ruptures, the
are released into the bloodstream where they move
on to other tissue cells. This provides for rapid
proliferation.
The bloodstream trypomastigote rare in chronic
disease. Visible flagellum. Does not divide
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Trypanosoma cruzi host-cell interaction
INVASION Essential for survival and replication
in the vertebrate host. In addition it helps with
immune evasion Active process associated with
parasite energy and host cell protein
synthesis. Complex process involving a variety of
factors.
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T. cruzi morphology

• Organelles present in other eukaryotes nucleus,
  Golgi, ER, mitochondria
• Unusual organelles
• Kinetoplast Region of the mitochondrion
  containing highly packed DNA (20 of total)
• glycosomes peroxisomes, contain all the
  glycolyitc enzymes
• reservosomes pre-lysosomal compartment
• cytostome mouth
• acidocalcisome calcium storage
• contractile vacuole similar to the CV in amebas
• Flagellum
• Paraflagellar rod
• Subpellicular microtubules

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CHAGAS DISEASE

• Acute form 7-10 days incubation period. Often
  in children chagoma, Romaña sign, flu-like
  symptoms, myocarditis, encephalitis,
  lymphadenoathy, enlargement of liver and spleen.
  
• Indeterminate form seropositivity but no
  symptoms or physical abnormalities, normal ECG.
  Aprox. 70-80 of infected individuals
• Chronic form (months to decades after the first
  infection)
• heart disease 10-30 of cases sudden death,
  aneurism
• intestinal form megaesophagus, megacolon

Romaña sign
Chagoma
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CHAGAS DISEASE
The parasite enters the cells at the initial site
of entry. Transforms into amastigote and
duplicates. The cell ruptures and release more
parasites. The combination of the parasitized
cells plus the inflammatory reaction of the host
is responsible for the initial pathology
observed.
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CHAGAS DISEASEACUTE FORM
Most of the people does not have clear symptoms
and do not go to the doctor. Large spectrum of
manifestations. Parasite populations are
polymorphic. Some studies show that genetically
distinct populations display characteristic
tissue tropism. Host immune response is also
crucial Salvador Mazza said in the year 1930
that in the presence of any infectious
undetermined case in an endemic area, one should
always think of Chagas. Relationship between
parasites and local inflammatory lesions. Cardiac
pathology involving monocyte infiltration,
degenerative myocarditis, and cyst formation.
Hepatosplenomegaly and edema specially in
children.
Hepatosplenomegaly
Edema
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Acute Chagas' myocarditis in a 6-year-old
Brazilian boy.
Posteroanterior (PA) (A) and left anterior
oblique (LAO) (B) views of the chest show marked
generalized cardiac enlargement with dilatation
of all chambers. The hilar areas are not
prominent and the lungs show no evidence of
vascular congestion. Fluoroscopically the cardiac
pulsations were decreased. The child had dyspnea
and abdominal pain for 4 months and pitting edema
in the lower legs for 2 months. The jugular veins
were distended and the heart sounds were weak
with a systolic murmur in the mitral area. The
liver was palpable 10 cm below the right costal
margin. Chagas' serology was positive. (Courtesy
of Dr. Clovis Simao, Sao Paulo).
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CHAGAS DISEASE
CHRONIC FORM Parasites are difficult to find, so
the cause of pathology is controversial. Although
an autoimmune origin was proposed it was found
that chronic pathology is associated with the
presence of the parasite. Affected patients with
the cardiac form have a chronic inflammatory
process that involves all heart chambers,
conduction system damage and often an apical
aneurysm. The pathogenesis is hypothesized to
involve parasite persistence in cardiac tissue
and immune-mediated myocardial injury. Abnormaliti
es Early Conduction system abnormalities Later
complex ventricular extrasystoles and ventricular
tachycardia Sinus node dysfunction Heart
block Clinical signs palpitations, presyncope,
syncope, and high risk of sudden death
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Cineventriculogram of a 49-year old male with
Chagas Heart Disease
The picture shows the apical aneurysm (sacular)
with normal coronary arteries From PLOS Medicine
4e332 (2007)
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Chronic Chagas' myocardiopathy.
(C) Posterior half of a heart showing generalized
dilatation of the atria and ventricles and the
aneurysm at the apex of the left ventricle. The
interventricular septum and ventricular walls are
thin, as is the complexity of trabeculae near the
insertion of the papillary muscles. (D) Moderate
generalized cardiac enlargement is noted on PA
view of the chest of the same patient. Note the
clear lung fields with no pulmonary vascular
congestion or pleural fluid. Clinically the
patient had shortness of breath, cardiac
palpitations, precordial pain and pitting edema
in the legs for 15 days prior to admission. The
ECG showed supraventricular tachycardia and
evidence of anteroseptal necrosis, with extension
to the diaphragmatic area. Chagas' serology was
positive. The patient progressively deteriorated
and at autopsy the heart weighed 420 gm and
showed generalized enlargement with apical
aneurysm. (Courtesy of Dr. Clovis Simao, Sao
Paulo). http//tmcr.usuhs.mil/tmcr/chapter4/ccm2.h
tm
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CHAGAS DISEASE

GASTROINTESTINAL DISEASE Gastrointestinal
involvement is less common than heart
disease. Results from damage to intramural
neurons and predominantly affects the esophagus,
colon or both. The esophageal effects involves a
spectrum from asymptomatic motility disorders
through mild achalasia to severe megaesophagus.
Manifestations include dysphagia, odynophagia,
esophageal reflux, weight loss, aspiration, cough
and regurgitation. Increased risk for esophageal
carcinoma. Colonic involvement leads to
prolonged constipation, abdominal pain and
fecaloma. Increased risk of volvulus and
consequent bowel ischemia.
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INTESTINAL FORM
Massive megaesophagus in an adult Brazilian man
with chronic dysphagia. (A) A soft tissue mass
widens and projects almost to the lateral chest
wall. The esophagus is distended with fluid and a
minimal amount of air. Barium swallow (B) shows
the full extent of the markedly dilated mid- and
lower esophagus with barium having settled to the
bottom of the fluid column. The contracted distal
esophageal segment follows a tortuous course to
the esophagogastric junction. This PA film of the
chest was taken 30 minutes after ingestion of
barium, indicating marked delay in esophageal
emptying due to virtually complete loss of
peristalsis within the dilated, atonic esophagus.
http//tmcr.usuhs.mil/tmcr/disease.htm
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INTESTINAL FORM
Colon the entire colon may be enlarged.
Constipation is a common complaint.
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CHAGAS DISEASE
CONGENITAL INFECTION Approx 1-10 of pregnancies
in women with chronic T. cruzi infection, the
infant is born with congenital infection Most
infected newborns are asymptomatic or have
non-specific finding such as low birth weight,
prematurity or low Apgar scores. Other signs
hepatosplenomegaly, anemia and thrombocytopenia Se
rious manifestations myocarditis,
meningoencephalitis and respiratory distress
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CHAGAS DISEASE AND AIDS
Individuals with HIV and chronic T. cruzi
infection may experience a reactivation which is
most commonly manifested by meningoencephalitis.
It may be difficult to distinguish it from
toxoplasmosis. A reactivation myocarditis is the
second most common manifestation..
Diagnostic test findings in a patient with
chagasic encephalitis. Left. Contrast-enhanced,
T1-weighted magnetic resonance imaging (axial
cut) of the brain showing multiple ring-enhancing
lesions. Right. Brain biopsy showing rod
kinetoplasts indicative of the amastigote form of
Trypanosoma cruzi. From Annals of Internal
Medicine (2006) 144941
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Drugs against Chagas Disease
Nifurtimox (Lampit) Nitro derivative that acts
through the production of toxic free radicals.
The parasite is more sensitive due to deficiency
in their antioxidant enzyme repertoire. However,
the problem is frequent toxicity (anorexia,
nausea, vomiting, peripheral neuropathy, skin
reactions, CNS effects). In addition is partially
effective in acute stage (strain variability) and
inactive in the chronic stage of disease.
Requires prolonged treatment (up to 90 days)
98-10 mg/Kg per day). Carcinogenic and mutagenic
(? not in humans) Future availability and cost
(Bayer) is a problem. Not available in the US or
Canada. Benznidazole (Radanil) the mode of
action is not completely clear. studied in
detail. It appears to inhibit protein and RNA
synthesis. Frequent toxicity (allergic skin
reactions, peripheral neuropathy, leucopaenia,
convulsions) Partially effective in acute stage
(strain variability) Inactive in chronic stage of
disease Prolonged treatment (up to 60 days) (5-7
mg/kg per day) Carcinogenic and mutagenic (? not
in humans) Future availability and cost (Roche)
is a problem.
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• Diagnosis
• Detection of parasites
• detection in blood (rare)
• hemoculture
• xenodiagnosis
• Immunological
• indirect hemaglutination
• immunofluorescence
• ELISA
• complement fixation
• complement-mediated lysis
• Molecular
• PCR
• Evidence of clinical disease

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T. cruzi epidemiology
Infects over 100 mammalian species Reservoir
hosts rodents, armadillos, dogs,
cats Transmitted by hemiptera from the family
Reduviidae, such as Triatoma, Rhodnius and
Panstrongylus (gt30 species) Endemic in Central
and South America Aprox. 16-18 million people
infected/ 40 millions at risk of infection.
Annual mortality rate is 50,000 Chagas disease
remains a serious health and economic problem in
Latin America, specially for the rural poor
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The type of construction favors the growth of the
insect vector
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Chagas Disease Vector Control
Residual spraying with pyrethroid insecticides
Source WHO/TDR
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Use of insecticidal paint
http//www-nt.who.int/tropical_diseases/databases/
imagelib.pl?imageid9105006
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www.who.int
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OTHER CONTROL MEASURES

• Improvement of human dwellings
• Health education
• Separation of animal stalls from house
• Gentian violet in blood for transfusions
• Listen this song in utube (is in spanish)
• http//www.youtube.com/watch?vXx8jiSs6OCw

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Prevention of transmission through blood
transfussion
Transfusion Transmitted Chagas' disease reported
in endemic areas for almost 40 years. In recent
years, several cases of Transfusion Transmitted
Chagas' disease have been reported in the US and
Canada. The risk of T. cruzi transmission
through transfusion depends on the prevalence of
asymptomatic parasitemia in blood donors and the
immunologic status of recipients. Donors who
were born or have lived in endemic areas for more
than 1 year are more likely to be positive for T.
cruzi antibodies. In endemic areas transmission
measures have included screening of blood donors.
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PAHO Regional Program on Chagas Disease
Mission Carry out technical-cooperation
activities in countries endemic for Chagas
diseases through subregional integration schemes
covering for endemic geographic spaces
(illustrated on map), via subregional
initiatives Interrupt household vectoral
transmission of Trypanosome cruzi through
integrated control schemes, with their objectives
adjusted to the epidemiological reality of each
country or subregion. Contribute to the
interruption of transfusional transmission of
Trypanosoma cruzi. Provide support to any
efficacious advancements proposed by the
countries in the areas of diagnostics,
management, and surveillance of Chagas disease.