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  Image Trypanosoma cruzi crithidiajpeg
  Caption Photomicrograph of Giemsa -stained ''Trypanosoma cruzi'' Crithidia ( CDC )
  ICD10 B57
  ICD9


Chagas disease (also called '''''American trypanosomiasis''''') is a human Tropical Parasitic Disease which occurs in The Americas , particularly in South America . Its Pathogen ic Agent is a Flagellate Protozoa n named '' Trypanosoma Cruzi '', which is transmitted to humans and other Mammal s mostly by Hematophagous Assassin Bug s of the subfamily Triatominae (Family Reduviidae ). Those insects are known by numerous common names varying by country, including benchuca, vinchuca, kissing bug, chipo, barbeiro, et cetera. The most common insect species belong to the genera '' Triatoma '', '' Rhodnius '', and '' Panstrongylus ''. Other forms of transmission are possible, though, such as ingestion of food contaminated with Parasite s, Blood Transfusion and Fetal transmission.

''Trypanosoma cruzi'' is a member of the same Genus as the infectious agent of African Sleeping Sickness , but its clinical manifestations, geographical distribution, life cycle and insect Vectors are quite different.


HISTORY

The disease was named after the Brazil ian Physician and Infectologist Carlos Chagas , who first described it in 1909, but the disease was not seen as a major Public Health problem in humans until the 1960s. He discovered that the intestines of Triatomidae harbored a flagellate protozoan, a new species of the '' Trypanosoma '' genus, and was able to prove experimentally that it could be transmitted to Marmoset monkeys which were bitten by the infected bug.

Chagas named the , Vector , Host , clinical manifestations, and Epidemiology . Nevertheless, he at least believed falsely until 1925, that the main infection route is by the bite of the insect and not by the Feces , as it was proposed by his colleague Emile Brumpt 1915 and assured by Silveira Dias 1932, Cardoso 1938 and Brumpt himself 1939.

On another historical point of view, it has been hypothesized that Charles Darwin might have suffered from this disease as a result of a bite of the so-called Great Black Bug of the Pampas (vinchuca) (see Illness Of Charles Darwin ). 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 in general 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 Symptom s, becoming very incapacitated for much of the rest of his life. Attempts to test Darwin's remains at the Westminster Abbey by using modern PCR techniques were met with a refusal by the Abbey's Curator .


EPIDEMIOLOGY AND GEOGRAPHICAL DISTRIBUTION

(A:Endemic zones)]]
Chagas disease currently affects 16-18 million people, killing around 20,000 people annually and with some 100 million at risk of acquiring the disease. Chronic Chagas disease remains a major health problem in many s and Raccoon s as far as North Carolina {Link without Title} .

The disease is distributed in the Americas , ranging from the southern United States to southern Argentina , mostly in poor, Rural areas of Central and South America .

The disease is almost exclusively found in rural areas, where the Triatominae can breed and feed on the Natural Reservoir s (the most common ones being Opossum s and Armadillo s) of ''T.cruzi''. Depending on the special local interactions of the vectors and their hosts, other infected humans, domestic animals like Cat s, Dog s, Guinea Pig s and wild animals like Rodent s, Monkey s, Ground Squirrel s ('' Spermophilus Beecheyi '') and many other could also serve as important parasite reservoirs. Though Triatominae bugs feed on birds, these seem to be immune against infection and therefore are not considered to be a ''T. cruzi'' reservoir, but they remain suspicious to be a constant feeding resource for the vectors in the surroundings of human stay.

The popular name of the vector insect in Brazil, ''barbeiro'' ("the barber"), so called because it sucks the blood at night by biting the face of its victims, reveals some of its habits. The insects, who develop a predominantly domiciliary and and Thatch . A Mosquito Net , wrapped under the mattress, will provide protection in these situations, when the adult insect might sail down from above, but one of the five nymphal stages ( Instars ) could crawl up from the floor.

Even when the colonies of the insects are eradicated in the house and around (domestic animal shelters), they again can arrive (also by flying short distances) from nearby nature (possibly a Palm Tree ), where animals and the insect which are part of the ancient, natural sylvatic infection cycle use to live. This especially can happen in zones with mixed open savannah, clumps of trees, etc., interspersed by human habitation.

Dense vegetation, like in tropical Rain Forest s, 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 out by economical exploitation and human habitation, such as in newly Deforested areas of the Amazon region, this may occur, when the insects are searching for a new prey.


CLINICAL MANIFESTATIONS


The human , and the chronic stage that may develop over 10 years.

In the acute phase, a local skin nodule called a ''chagoma'' can appear at the site of Inoculation . When the inoculation site is the Conjunctival mucous membranes, the patient may develop unilateral periorbital edema, conjunctivitis, and preauricular lymphadenitis. This constellation of findings is referred to as Romaña's sign. The acute phase is usually Asymptomatic , but can present with manifestations that include Fever , Anorexia , Lymphadenopathy , mild Hepatosplenomegaly , and Myocarditis . Some acute cases (10 to 20%) resolve over a period of 2 to 3 months into an asymptomatic chronic stage, only to reappear after several years.

The symptomatic chronic stage may not occur for years or even decades after initial infection. The disease affects the Nervous System , Digestive System and Heart . Chronic infections result in various neurological disorders, including Dementia , damage to the heart muscle ( Cardiomyopathy , the most serious manifestation), and sometimes dilation of the Digestive Tract ( Megacolon and Megaesophagus ), as well as Weight Loss . Swallowing difficulties may be the first symptom of digestive disturbances and may lead to Malnutrition . After several years of an asymptomatic period, 27% of those infected develop cardiac damage, 6% develop digestive damage, and 3% present peripheral nervous involvement. Left untreated, Chagas disease can be fatal, in most cases due to the Cardiomyopathy component.


INFECTION CYCLE

An infected triatomine insect vector takes a blood meal and releases Trypomastigote s in its feces near the site of the bite wound. By scratching the site of the bite, the victim allows trypomastigotes to enter the host through the wound, or through intact mucosal membranes, such as the Conjunctiva . Inside the host, the trypomastigotes invade cells, where they differentiate into intracellular Amastigote s. The amastigotes multiply by Binary Fission and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes. Trypomastigotes infect cells from a variety of Biological Tissue s and transform into intracellular amastigotes in new infection sites. Clinical manifestations can result from this infective cycle and cell death at the target tissues. For example, it has been shown by Austrian-Brazilian pathologist Dr. Fritz Köberle in the 1950s at the Medical School Of The University Of São Paulo At Ribeirão Preto , Brazil (one of the excellent Medical Research centers on Chagas disease), that intracellular amastigotes destroy the intramural neurons of the Autonomic Nervous System in the intestine and heart, leading to megaintestine and heart Aneurysm s, respectively.

The bloodstream trypomastigotes do not replicate (different from the African Trypanosomes ). Replication resumes only when the parasites enter another cell or are ingested by another vector. The “kissing” bug becomes infected by feeding on human or animal blood that contains circulating parasites. Also the bugs might be able to spread the infection to each other through their
cannibalistic predatory behaviour. The ingested trypomastigotes transform into Epimastigote s in the vector’s midgut. The parasites multiply and differentiate in the midgut and differentiate into infective metacyclic trypomastigotes in the hindgut.

'' infection rate in Blood Bank s in Latin America vary between 3% and 53%, a figure higher than of HIV infection and Hepatitis B and C.
. Source: CDC]]

Alternative infection mechanism

Researchers suspected since 1991 {Link without Title} that the transmission of the trypanosome by the oral route might be possible, due to a number of micro-epidemics restricted to particular times and places (such as a farm or a family dwelling), particularly in non-endemic areas such as the .

Recently (March 2005) a new startling outbreak was recorded in the state of in Santa Catarina and urged everyone in this situation to submit to blood tests. They have prohibited the sale of sugar cane juice in the state until the situation is rectified.

The unusual severity of the disease outbreak has been blamed on a hypothetical higher parasite load achieved by the oral route of infection. Brazilian researchers at the Instituto Oswaldo Cruz , Rio De Janeiro , were able to infect Mice via a gastrointestinal tube with trypanosome-infected oral preparations.


LABORATORY DIAGNOSIS

Demonstration of the causal agent is the diagnostic procedure in acute Chagas disease. It almost always yields positive results, and can be achieved by:



TREATMENT

Medication for Chagas disease is usually only effective when given during the , and cannot be taken without medical supervision. A 10-year study of chronic administration of drugs in Brazil has revealed that these drugs are not totally effective, too, in removing Parasitemia {Link without Title} . Thus,
the decision about whether to use Antiparasitic Therapy should be individualized in consultation with an expert.

In the . Recently, direct Stem Cell Therapy of the heart muscle using Bone Marrow cell transplantation has been shown to dramatically reduce risks of heart failure in Chagas patients {Link without Title} .
Patients have also been shown to benefit from the strict prevention of reinfection, though the reason for this is not yet clearly understood.

Some examples for the struggle for advances:


PREVENTION

'' (Kissing Bug)]]
A reasonably effective Vaccine was developed in Ribeirão Preto in the 1970s, using cellular and subcellular fractions of the parasite, but it was found economically unfeasible. More recently, the potential of DNA vaccines for Immunotherapy of acute and chronic Chagas disease is being tested by several research groups.

Prevention is centered on fighting the vector (''Triatoma'') by using sprays and paints containing Insecticide s (synthetic Pyrethroids ), and improving housing and sanitary conditions in the rural area. 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. If the traveller intends to travel to the area of prevalence, he/she should get information on endemic rural areas for Chagas disease in traveller advisories, such as the CDC .

In most countries where Chagas disease is endemic, Testing for Blood Donors is already mandatory, since this can be an important route of transmission.
In the past, blood donors were mixed with 0,25 g/L of Gentian Violet successfully to kill parasites.

With all these measures, some landmarks were achieved in the fight against Chagas disease in Latin America: a reduction by 72% of the incidence of human infection in children and young adults in the countries of the Initiative of the Southern Cone , and at least two countries ( Uruguay , in 1997, and Chile , in 1999), were certified free of vectorial and transfusional transmission. In Brazil, with the largest population at risk, 10 out of the 12 endemic states were also certified free.

Some stepstones of vector control:


ORIGINAL PUBLICATION



REFERENCES



FURTHER READING


There is a special issue of the International Symposium to commemorate the 90th anniversary of the discovery of Chagas disease (Rio de Janeiro, April 11-16, 1999) in ''Memórias do Instituto Oswaldo Cruz'', Vol. 94, Suppl. I, 1999 ( Table of contents , with full text papers available in PDF)


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