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| Credit: wikipedis.org |
Chagas disease, also known as American trypanosomiasis,
is a tropical parasitic
disease caused by the protozoan Trypanosoma
cruzi. It
is spread mostly by insects known as Triatominae or
kissing bugs. The
symptoms change over the course of the infection. In the early stage, symptoms
are typically either not present or mild, and may include fever, swollen lymph
nodes, headaches, or local swelling at the site of the bite. After
8–12 weeks, individuals enter the chronic phase of disease and in 60–70% it
never produces further symptoms. The
other 30 to 40% of people develop further symptoms 10 to 30 years after the
initial infection, including
enlargement of the ventricles of the heart in 20 to 30%,
leading to heart failure. An enlarged
esophagus or an enlarged colon may also occur in 10% of people.
T. cruzi is commonly spread to humans and other mammals
by the blood-sucking "kissing bugs" of the
subfamily Triatominae. These
insects are known by a number of local names, including: vinchuca in
Argentina, Bolivia, Chile and Paraguay, barbeiro (the barber)
in Brazil, pito in Colombia, chinche in Central America,
and chipo in Venezuela. The
disease may also be spread through blood
transfusion, organ transplantation, eating food
contaminated with the parasites, and by vertical transmission (from a mother to
her fetus). Diagnosis
of early disease is by finding the parasite in the blood using a microscope. Chronic
disease is diagnosed by finding antibodies for T.
cruzi in the blood.
Prevention mostly involves eliminating kissing bugs and
avoiding their bites. Other
preventative efforts include screening blood used for transfusions. A
vaccine has not been developed as of 2013. Early
infections are treatable with the medication benznidazole or nifurtimox. Medication
nearly always results in a cure if given early, but becomes less effective the
longer a person has had Chagas disease. When
used in chronic disease, medication may delay or prevent the development of
end–stage symptoms. Benznidazole
and nifurtimox cause temporary side effects in up to 40% of people including
skin disorders, brain toxicity, and digestive system irritation.
It is estimated that 7 to 8 million people, mostly in Mexico, Central
America and South America, have Chagas disease as of 2013. In
2006, Chagas was estimated to result in 12,500 deaths per year. Most
people with the disease are poor, and
most people with the disease do not realize they are infected. Large-scale
population movements have increased the areas where Chagas disease is found and
these include many European countries and the United States. These
areas have also seen an increase in the years up to 2014. The
disease was first described in 1909 by Carlos
Chagas after whom it is named. It
affects more than 150 other animals.
Signs and symptoms
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| Credit: wikipedia.org (An acute
Chagas disease infection with swelling of the right eye (Romaña's sign).) |
The human disease occurs in two stages: an acute stage,
which occurs shortly after an initial infection,
and a chronic stage that develops over many
years.
The acute phase lasts for the first few weeks or months of
infection. It usually occurs unnoticed because it is symptom-free or exhibits
only mild symptoms that are not unique to Chagas disease. These can include
fever, fatigue, body aches, muscle pain, headache, rash, loss of appetite,
diarrhea, nausea, and vomiting. The signs on physical examination can include
mild enlargement of the liver or spleen, swollen glands, and local swelling
(a chagoma)
where the parasite entered the body.
The most recognized marker of acute Chagas disease is called
Romaña's sign, which includes swelling of the eyelids on the side of the face
near the bite wound or where the bug feces were deposited or accidentally
rubbed into the eye. Rarely, young children, or adults may die from the acute
disease due to severe inflammation/infection of the heart muscle (myocarditis)
or brain (meningoencephalitis). The
acute phase also can be severe in people with weakened immune systems.
If symptoms develop during the acute phase, they usually
resolve spontaneously within three to eight weeks in approximately 90% of
individuals. Although
the symptoms resolve, even with treatment the infection persists and enters a
chronic phase. Of individuals with chronic Chagas disease, 60–80% will never
develop symptoms (called indeterminate chronic Chagas disease), while
the remaining 20–40% will develop life-threatening heart and/or digestive
disorders during their lifetime (called determinate chronic Chagas
disease). In 10% of individuals, the disease progresses directly from the acute
form to a symptomatic clinical form of chronic Chagas disease.
 |
| Credit: wikipedia (Large scale
anatomy of a heart that has been damaged by chronic Chagas disease – see
also: Chagas heart, radiology) |
The symptomatic (determinate) chronic stage affects
the nervous system, digestive
system and heart. About two-thirds of people with chronic symptoms
have cardiac damage, including dilated cardiomyopathy, which causes heart
rhythm abnormalities and may result in sudden death. About one-third of
patients go on to develop digestive
system damage, resulting in dilation of the digestive
tract (megacolon and megaesophagus),
accompanied by severe weight loss. Swallowing difficulties
(secondary achalasia) may be the first symptom of digestive
disturbances and may lead to malnutrition.
20% to 50% of individuals with intestinal involvement also
exhibit cardiac involvement. Up
to 10% of chronically infected individuals develop neuritis that
results in altered tendon reflexes and sensory impairment. Isolated cases
exhibit central nervous system involvement, including dementia,
confusion, chronic encephalopathy and sensory and motor deficits.
The clinical manifestations of Chagas disease are due to
cell death in the target tissues that occurs during the infective cycle, by
sequentially inducing an inflammatory response, cellular lesions, and fibrosis. For
example, intracellular amastigotes destroy the intramural neurons of
the autonomic nervous system in the
intestine and heart, leading to megaintestine and heart aneurysms,
respectively. If left untreated, Chagas disease can be fatal, in most cases due
to heart muscle damage. Read more >>
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