Category: Illness or disabilities
Introduction and description
Chagas disease or American trypanosomiasis, is a tropical parasitic disease caused by the protozoan Trypanosoma cruzi and spread mostly by insects known as Triatominae or kissing bugs.
Chagas disease affects 8 to 10 million people living in endemic Latin American countries, with an additional 300,000–400,000 living in nonendemic countries, including Spain and the United States.
An estimated 41,200 new cases occur annually in endemic countries, and 14,400 infants are born with congenital Chagas disease annually. In 2010 it resulted in approximately 10,300 deaths up from 9,300 in 1990.
Large-scale population movements as well as inter continental travel, have increased the areas where cases of Chagas disease are found and these now include many European countries and the United States. These areas have also seen an increase in the years up to 2014.
... Due to the increased migration of peoples, Chagas disease has been on the uprise outside Latin America, including in Europe. .... In the Netherlands, the number of immigrants who would serologically test positive for American trypanosomiasis is estimated to be between 726 and 2929. Healthcare providers in the Netherlands may encounter patients who have Chagas disease more and more frequently. The screening of pregnant women and blood donors at risk for American trypanosomiasis should be considered. PMID: 21527056
Chagas disease, a neglected tropical disease that due to population movements is no longer limited to Latin America, threatens a wide spectrum of people (travellers, migrants, blood or organ recipients, newborns, adoptees) also in non-endemic countries where it is generally underdiagnosed. In Italy, the available epidemiological data about Chagas disease have been very limited up to now, although the country is second in Europe only to Spain in the number of residents from Latin American. Among 867 at-risk subjects screened between 1998 and 2010, the Centre for Tropical Diseases in Negrar (Verona) and the Infectious and Tropical Diseases Unit, University of Florence found 4.2% patients with positive serology for Chagas disease (83.4% of them migrants, 13.8% adoptees). ... Among 214 Latin American pregnant women,three were infected (resulting in abortion in one case). PMID: 21944554
The disease is present in 18 countries on the American continents, ranging from the southern United States to northern Argentina. Chagas exists in two different ecological zones. In the Southern Cone region, the main vector lives in and around human homes. In Central America and Mexico, the main vector species lives both inside dwellings and in uninhabited areas. In both zones, Chagas occurs almost exclusively in rural areas, where triatomines breed and feed on the over 150 species from 24 families of domestic and wild mammals, as well as humans, that are the natural reservoirs of T. cruzi.
Several landmarks have been achieved in the fight against Chagas disease in Latin America, including a reduction by 72% of the incidence of human infection in children and young adults in the countries of the Southern Cone Initiative, and at least three countries (Uruguay, in 1997, and Chile, in 1999, and Brazil in 2006) have been certified free of vectorial and transfusional transmission. In Argentina, vectorial transmission has been interrupted in 13 of the 19 endemic provinces, and major progress toward this goal has also been made in both Paraguay and Bolivia.
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. If left untreated, Chagas disease can be fatal, in most cases due to heart muscle damage.
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, headache, rash, loss of appetite, diarrhoea, 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 faeces 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 (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.
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.
T. cruzi is 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.
In Chagas-endemic areas, the main mode of transmission is through an insect vector called a triatomine bug. A triatomine becomes infected with T. cruzi by feeding on the blood of an infected person or animal. During the day, triatomines hide in crevices in the walls and roofs. The bugs emerge at night, when the inhabitants are sleeping. Because they tend to feed on people's faces, triatomine bugs are also known as "kissing bugs". After they bite and ingest blood, they defecate on the person. Triatomines pass T. cruzi parasites (called trypomastigotes) in feces left near the site of the bite wound.
Scratching the site of the bite causes the trypomastigotes to enter the host through the wound, or through intact mucous membranes, such as the conjunctiva. Once inside the host, the trypomastigotes invade cells, where they differentiate into intracellular amastigotes. The amastigotes multiply by binary fission and differentiate into trypomastigotes, which are then released into the bloodstream. This cycle is repeated in each newly infected cell. Replication resumes only when the parasites enter another cell or are ingested by another vector.
T. cruzi can also be transmitted through blood transfusions. With the exception of blood derivatives (such as fractionated antibodies), all blood components are infective. The parasite remains viable at 4 °C for at least 18 days or up to 250 days when kept at room temperature. It is unclear whether T. cruzi can be transmitted through frozen-thawed blood components.
Blood transfusion was formerly the second-most common mode of transmission for Chagas disease, but the development and implementation of blood bank screening tests has dramatically reduced this risk in the last decade. Blood donations in all endemic Latin American countries undergo Chagas screening, and testing is expanding in countries, such as France, Spain and the United States, that have significant or growing populations of immigrants from endemic areas. In Spain, donors are evaluated with a questionnaire to identify individuals at risk of Chagas exposure for screening tests.
Mother to baby transmission
Chagas disease can also be spread congenitally (from a pregnant woman to her baby) through the placenta, and accounts for approximately 13% of stillborn deaths in parts of Brazil. The disease can also be spread via breast milk.
Oral transmission is an unusual route of infection, but has been described. In 1991, farm workers in the state of Paraíba, Brazil, were infected by eating contaminated food; transmission has also occurred via contaminated açaí palm fruit juice and garapa. A 2007 outbreak in 103 Venezuelan school children was attributed to contaminated guava juice.
The disease may also be spread through organ transplantation and by accidental laboratory exposure.
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. The presence of T. cruzi is diagnostic of Chagas disease. It can be detected by microscopic examination of fresh anticoagulated blood, or its buffy coat, for motile parasites; or by preparation of thin and thick blood smears stained with Giemsa, for direct visualization of parasites. Microscopically, T. cruzi can be confused with Trypanosoma rangeli, which is 'not known to be pathogenic in humans'. Isolation of T. cruzi can occur by inoculation into mice, by culture in specialized media (for example, NNN, LIT); and by xenodiagnosis, where uninfected Reduviidae bugs are fed on the patient's blood, and their gut contents examined for parasites.
Various immunoassays for T. cruzi are available and can be used to distinguish among strains (zymodemes of T.cruzi with divergent pathogenicities). These tests include: detecting complement fixation, indirect hemagglutination, indirect fluorescence assays, radioimmunoassays, and ELISA. Alternatively, diagnosis and strain identification can be made using polymerase chain reaction (PCR).
Prevention mostly involves eliminating kissing bugs and avoiding their bites. Other preventative efforts include screening blood used for transfusions.
Dense vegetation (such as that of tropical rainforests) and urban habitats are not ideal for the establishment of the human transmission cycle.
However, in regions where the sylvatic habitat and its fauna are thinned by economic exploitation and human habitation, such as in newly deforested areas, piassava palm culture areas [Piassaba fiber is made into brooms, baskets, and other products. This plant is a natural habitat of the Rhodnius brethesi, which is a potential vector of Chagas disease], and some parts of the Amazon region, a human transmission cycle may develop as the insects search for new food sources.
Even when colonies of insects are eradicated from a house and surrounding domestic animal shelters, they can re-emerge from plants or animals that are part of the ancient, sylvatic (referring to wild animals) infection cycle. This is especially likely in zones with mixed open savannah, with clumps of trees interspersed by human habitation.
For urban dwellers, spending vacations and camping out in the wilderness or sleeping at hostels or mud houses in endemic areas can be dangerous; ‘a mosquito net is recommended’. Some measures of vector control include:
- A yeast trap can be used for monitoring infestations of certain species of triatomine bugs (Triatoma sordida, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus).
- "Promising results have been gained with the treatment of vector habitats with the fungus Beauveria bassiana."
There are two approaches to treating Chagas disease, antiparasitic treatment, to kill the parasite; and symptomatic treatment, to manage the symptoms and signs of the infection.
Antiparasitic treatment is most effective early in the course of infection. Drugs include azole or nitro derivatives, such as benznidazole or nifurtimox. Both agents are limited in their capacity to effect parasitologic cure (a complete elimination of T. cruzi from the body), especially in chronically infected patients, and resistance to these drugs has been reported. When used in chronic disease they 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.
Treatment of chronic infection in women prior to or during pregnancy does not appear to reduce the probability the disease will be passed on to the infant.
In the chronic stage, treatment involves managing the clinical manifestations of the disease. For example, pacemakers and medications for irregular heartbeats. The disease cannot be cured in this phase.
How it works
People getting hallucinations, visions etc usually get them through the brain damage caused by the parasite.
It has been hypothesized that Charles Darwin might have suffered from Chagas disease as a result of a bite of the so-called great black bug of the Pampas (vinchuca). The episode was reported by Darwin in his diaries of the Voyage of the Beagle as occurring in March 1835 to the east of the Andes near Mendoza. Darwin was young and generally in good health, though six months previously he had been ill for a month near Valparaiso, but in 1837, almost a year after he returned to England, he began to suffer intermittently from a strange group of symptoms, becoming incapacitated for much of the rest of his life. Attempts to test Darwin's remains at Westminster Abbey by using modern PCR techniques were met with a refusal by the Abbey's curator, so we don’t actually know one way or the other.
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