When Hiking Through Latin America, Be Alert to Chagas' Disease

Valle de los Naranjos, Venezuela. It is late afternoon, the sun is sinking behind the mountains, bringing the first shadows of evening. Down in the valley a campesino is still tilling the soil, and the stillness of the approaching night is broken only by a light plane, a crop duster, which periodically flies over head and disappears further down the valley.

Bertoldo, the pilot, is on his final dusting run of the day when suddenly the engine dies. The world flashes before his eyes as he fights to clear the last row of palms. The old duster rears up, just clipping the last trees as it somersaults into the forest. Although death does not claim the pilot at this moment, his fate is sealed when the campesino drags him, stunned but unhurt, from the plane. He gratefully accepts the peasant's offer to spend the night in his home, a poorly constructed dwelling of the kind common in rural areas of Latin America and known as el rancho (the hut), with walls of adobe, a dirt floor and a roof of palm fronds.

On his ride back to Valencia the next day, Bertoldo reflects on his good fortune. Only three months earlier he had come from Italy, and he was now employed in his new country in a job he liked. In the accident he had not even been scratched, and other than the wrecked plane he had nothing but a few insect bites to show for his adventure.

Bertoldo's luck was short-lived. Two weeks after the night spent in the campesino's hut, he came down with a fever and the right side of his face became red and puffy. He grew progressively weaker, and a few weeks later he was in heart failure. As the result of the bite of an insect known as vinchuca, Bertoldo has become infected by a parasite, Trypanosoma cruzi, the cause of Chagas'disease. Three months later Bertoldo was dead.


The carrier of the parasite that causes Chagas'disease is a smooth, oval-shaped insect, brownish in colour, and belongs to the subfamily of Triatominae of the Reduviidae family (order Hemiptera). The insect (see illustration below "a" - Rhodnius prolixus), two centimeters long, has a long, narrow, cone-shaped head with two antennae and a proboscis which curves under the head and ends in a groove in the upper part of the thorax. On the lateral aspects of the abdomen are narrow stripes of light yellow or red alternating with dark brown. The insect has a limited flight range: although it is furnished with two pairs of wings, these are used mainly as a parachute. One of the insect's aliases is "vinchuca," deriving from the Quechua word huinchucum, meaning "one who lets himself fall down."

Both female and male depend on the blood of vertebrates for survival. The vinchuca is nocturnal, hiding during the day in crevices of walls and among the palm fronds of the roof, coming out at night to feed. It is attracted to exposed parts of the body and has a preference for the face - it is actually called barbeiro (barber) in Brazil. In Europe and North America it is called kissing bug or, more appropriately, assassin bug.

When the vinchuca finds the exposed face of a human victim, it places itself in the feeding position, lifts the proboscis and flexes the distal segment upwards, and releases from the proboscis a stylet with fine teeth, with which is perforates the skin. A second stylet, smooth and hollow, taps a blood vessel. This feeding process lasts at least twenty minutes, during which the vinchuca ingests many times its own weight in blood.

During feeding defecation occurs, contaminating the bite wound with feces containing parasites which the vinchuca has ingested as a result of having previously bitten an infected human or animal. The irritation of the bite causes the sleeping victim to rub the site with his fingers, thus facilitating the introduction of the organisms into the blood. The parasites are also capable of penetrating the intact thin layer of cells covering the mucosa of the mouth, nostrils and conjunctiva.


In primeval times, sylvatic animals, which naturally harbor the parasite Trypanosoma cruzi, were the only source of blood for the vinchuca. The opossum, the armadillo and various rodents are natural carriers of the parasite, a condition which makes Chagas'disease primarily a parasitic disease of the forest. When man intruded into the sylvatic ecological system, using palm trees in the construction of his dwellings, he unwittingly transported the insects, which breed and live in palm trees, and with them the parasites, into the heart of the rural community. An additional link provided the naturally infected opossum (Didelphis marsupialis) and rats (Rattus norvegicus, Rattus rattus) which haunt both the jungle and the natives' huts for food.

Of the one hundred and five species of Triatominae insects in the New World, only a few have adapted from the sylvatic to the domestic ecosystem. Some have been very successful, like the Rhodnius prolixus, which transmits the parasite causing Chagas'disease in Colombia and Venezuela, or Panstrongylus megistus in Brazil, or the most widespread vinchuca in South America, Triatoma infestans. In Central America the Triatoma dimidiata is the main carrier of the parasite. Triatominae species are also present throughout the southern United States and the Caribbean Islands, but none has successfully adapted to the domestic environment, and the infection is limited to the sylvatic ecosystem. Naturally, the construction of the North American home eliminates one major shelter used by the parasite-carrying vinchuca.

The transfer form the forest to the domestic setting assures the vinchuca of an immense source of blood from humans and domestic animals such as dogs, cats and guinea pigs, which are raised for food in Peru and Bolivia. (Cattle, goats, and pigs play a lesser role in the transmission of the disease). Of common domestic animals chickens and pigeons are immune to the infection, because their high blood temperature kills the parasites.

The domestic environment, with its plentiful supply of food, spurs the vinchuca to vigorous activity. The insect feeds more frequently, resulting in procreation so profuse that more than seven thousand vinchucas have been found living in one small hut.

When the vinchuca feeds on infected humans or animals it ingests the Trypanosomes (Gr.:trypanon = borer; sõma = body) - see the illustration of the Life Cycle of Chagas'Disease Parasite (1). These protozoa (Gr.:proto = primitive; zoon = animal) belong to the family of Trypanosomatidae, which also includes among its members the African Trypanosomes causing sleeping sickness.

Seen under the microscope the Trypanosoma cruzi has an elongate body with a whip-like flagellum on the anterior part which arises behind the nucleus and is attached to an undulating membrane running along the body.

The parasite evolves through a cycle of four phases, two phases in the vertebrate host and two in the gut of the insect. As soon as the Trypanosomes, at this stage called Trypomastigotes (Gr.:trypanon = borer; mastix = whip),(1), reach the gut of the vinchuca, they undergo a physical transformation into Promastigotes (Gr.:pros = in front; mastix = whip - the flagellum arises in front of the nucleus)(2), a phase during which they reproduce to form a new parasites called Epimastigotes (Gr.:epí; = near; mastix = whip - the flagellum arises near the nucleus)(3). These move to the rectum of the insect, resuming their former shape, and are expelled with the feces, infecting a new victim.

Having broached the skin, the Trypomastigotes invade the cells of the adjacent fat tissue, where they transform themselves into Amastigotes (Gr.: a = without; mastix = whip),(4). These round-shaped parasites reproduce in large numbers, forming a pseudo-cyst which distends the membrane of the fat cell until it bursts. Before the pseudo-cyst bursts, the Amastigotes will again assume the shape of Trypomastigotes, and, when released into the bloodstream, will rapidly invade the cells of various organs of the body most frequently the heart. There they will again multiply and grow into pseudo-cysts, which will burst and release the parasites to invade more healthy organ cells. The cycle repeats continually.


At the site of introduction of the parasite, usually the face, a hard violet-hued swelling appears after one week. This lesion is called "chagoma," after Dr. Carlos Chagas who first described it. In the majority of newly infected persons the chagoma affects the skin of the eyelid of the conjunctiva called "Romaña's sign". This represents the local reaction to the presence of the parasites, as the white blood cells and other elements of the body's defence system surround the clusters of parasites in the fat cells, destroying both fat cells and parasites.

Inevitable, however, some parasites escape and reach the bloodstream, invading heart, brain, liver and spleen, producing a generalized acute form of the disease in a about two percent of patients, mostly small children. Fever, a generalized rash, anorexia, diarrhea and vomiting, swollen lymph nodes and an enlarged liver are the symptoms of this acute phase. A severe complication, mostly in children, is meningoencephalitis which may lead to death.

In adults, the acute infection of the heart is the main manifestation, causing the heart to become enlarged in direct proportion to the intensity of the infection. As soon as the parasites enter the cells of the heart, the defence mechanisms begin to act. The tiny blood vessels dilate and plasma fluid escapes through the walls, inundating the spaces between the fibers of the heart muscle.

At the same time, white cells and other elements of the body's defence system will surround the infected fibers initiating the process of phagocytosis (Gr.: phagein = to eat; kútos = cell), crushing the parasites and the infected fibers to bits and swallowing them up with enzymes. The lesions thus produced decrease the contractility of the heart, reducing its output, which leads to heart failure. In this acute stage of the disease, death claims the life of ten percent of persons.

Bertoldo, the person in our story, died of this acute form of the disease. However, his death left a legacy to medical research. The strain (subspecies) of the parasites that killed him, named Bertoldo strain after him, is still being cultured in laboratories and used by scientists to study the action of the parasites on the heart.

However, in most cases of this acute infection of the heart, the symptoms subside within four to eight weeks and the victim continues to live an apparently healthy life, joining the large population of infected persons without any history of illness, which represents the majority of victims of Chagas'disease. In these persons, displaying no visible manifestation because the infection is slight, the condition may go unrecognized for years until a routine serological test discloses it, and unknowingly they contribute to the maintenance of the human reservoir of the infection and propagation of the life cycle of the parasite.

Although latent in its manifestations, the infection gradually progresses, surfacing after ten or twenty years in the form of chronic heart disease. During this time, the infected heart muscle fibers are slowly replaced by scar tissue, thinning the walls of the heart, sometimes so severely that, at the apex, it bulges out like a balloon (aneurysm). The scar tissue and the thinning of the walls affect the dynamics of the heart so severely that irreversible heart failure results with death occurring within a year. In some cases the parasites infect the fibers along the impulse-conducting system of the heart, causing disorders of the rhythm which may lead to sudden death unless a pacemaker is implanted.

Recent studies of chronic Chagas'disease patients indicate that not only the central nervous system but also the peripheral nervous system is irreversibly damaged by the parasites, causing pareses, convulsions, psychiatric abnormalities due to lesions in the brain tissue, and loss of motor sensitivity due to the damage to the spinal cord, and changes in bodily functions due to the damage caused to the autonomous nervous system.

In some areas of Brazil, chronic Chagas'disease often is manifested by the involvement of the digestive tract, called megaviscera, most commonly affecting the oesophagus and the colon. Difficulty in swallowing and severe constipation are signs of the involvement of these organs.


Chagas'disease is a serious health problem in rural Latin America. Between sixteen and eighteen million persons are infected and an estimated one hundred million are exposed to this insidious affliction, which impairs the physical activity of persons during the most productive period of their lives. It is a disease to which poor families are particularly subject and drastically reduces their life expectancy.

During the past thirty years, internal migration of rural populations has brought the infection to the periphery of cities like Buenos Aires and São Paulo, and in some countries the disease has reached the interior of urban areas like Cochabamba in Bolivia and Guayaquil in Ecuador.

Besides spreading the infection to towns, this migration of infected persons poses an additional risk through blood transfusions and organ transplants. Congenital transmission from infected mother to child occurs not only in rural areas but has become a problem in many urban areas. Poor people are eager to sell their blood and infected blood donors sometimes slip through the screening procedures set up by health authorities. Surveys of blood bank donors indicate a 60% infection rate in the Santa Cruz, Bolivia area and a rate of over 15% in northern Chile.

To asses the extent of Chagas'disease routine surveys are conducted throughout Latin America. In Buenos Aires, the National Health Department conducts daily screening programs, and for every five hundred people examined finds fifty unsuspecting persons with the infection.

In recent years, some breakthroughs have been made in the treatment of Chagas'disease. The drugs benznidazole and nifurtimox are effective in killing the parasites in the acute phase of the disease, but not all strains of the parasite are susceptible to the drugs.

Drug treatment in the early stages of the chronic phase of the disease may clear the patient of parasites. However, in chronic cases where lesions to the heart, brain and other organs have already occurred treatment with these drugs is not indicated as only the symptoms can be treated.


Improving housing, which requires extensive changes in existing economic and social conditions, is fundamental to any plan to control and prevent Chagas'disease. Some countries, such as Brazil and Venezuela, the two most active in control efforts, have national policies, but these are still far from being fully implemented throughout the country.

The destruction of parasite-carrying insects is another major step in the prevention of Chagas'disease. Trials with DDT have not been successful. The chemical gammexane (benzene hexachloride) has proven highly effective, but it must be applied at least three times a year since the eggs of the vinchuca are not affected by the chemical. Dieldrin, of the same chemical family, has also been used with good results.

Fumigant canisters and insecticidal paints have been successfully used in pilot studies in Argentina and Brazil. They have proven cost effective and efficient in reducing the vector infestation rates in rural dwellings.


Because of the nature of travel and accommodation, hikers and campers are particularly vulnerable to Chagas'disease. It is essential that they have some knowledge of the disease and how to avoid it. The same applies to people working in the interior of the country such as missionaries, archeologists, anthropologists, geologists and persons pursuing hobbies like bird watching.

Business travellers spending the night in the periphery or suburbs of cities ought at a minimum to check for insects in bedrooms.

Chagas'disease is insidious - an international traveller passing through endemic regions of Latin America may become infected, but may remain apparently healthy until the first signs of chronic heart disease appear years later. Chagas'disease is rarely diagnosed outside Latin America as the symptoms of this chronic form are the same as those of ischemic (coronary) heart disease.

At present, no drugs are available to prevent the establishment of the infection in the body. Vaccines are still in the experimental stages.

The extent of the infected areas is indicated on IAMAT's Chagas'disease Risk Chart (see below). The principal vectors in the given areas are also mentioned, including the altitude at which the risk may occur, as some insects, like the Triatoma infestans, still thrive at 3500 meters.



1907. State of Minas Gerais, Brazil. Carlos Chagas, while investigating malaria in Brazil, observed in the intestine of the Triatominae insects Panstrongylus megistus the presence of a protozoan which later he named Trypanosoma cruzi in honor of Dr. Oswaldo Cruz.

Two years later, he described the same parasite in the blood of a child with fever and enlarged lymph nodes of the neck. He proved the Trypanosoma cruzi to be the cause of a disease common in some areas of Brazil.

Dr. Chagas' discoveries made him the first person in the history of medicine to describe all the different aspects of the disease. He discovered the parasite and its developmental phases, described the vector and the cycle of infection, both in the sylvatic and rural environment, and clarified the signs and symptoms present in each phase of the disease.

However, Chagas believed that the parasites were introduced into the victim through the saliva of the infected vectors.

1912. E. Brumpt challenged his interpretation and proved that the parasites were transmitted through the feces eliminated by the insect during feeding.

1939. Tucumán, Argentina. The findings of Dr. Chagas did not attract the interest of the Brazilian medical profession until the Argentinean Salvador Mazza, conscious of the social impact of the disease, invited physicians from his country to collaborate with him on a systematic investigation of the extent of the disease.

1960. Experimental campaigns against the disease carried out in the 1950's in Latin America were replaced by systematic national programs, with Argentina, Brazil and Venezuela in the vanguard.

1993. After nearly a century, Latin America is still assessing the extent of its wounds.


Chagas'disease is highly endemic in rural and suburban areas below 3600 m in the following provinces: Catamarca, Chaco, Córdoba, Formosa, Jujuy, La Pampa, La Rioja, Mendoza, Salta, San Juán, San Luis, Santa Fe, Santiago del Estero, Tucumán. Risk is also present in rural areas (below 3600 m) in the provinces of Buenos Aires, Corrientes, Chubut (northern half), Entre Ríos, Misiones, Neuquen, Río Negro.

Main vectors: Triatoma infestans, Triatoma sordida.

The infection is present in the sylvatic ecosystem. Sporadic cases of human infections have been reported but the extent of Chagas'disease is unknown.

Main vector: Triatoma dimidiata.

Chagas'disease is endemic throughout rural and suburban areas below 3600 m, with very high human infection rates reported from the departments (including towns) of Cochabamba (including the city of Cochabamba), Sucre, Tarija and Santa Cruz.

Main vectors: Triatoma infestans, Triatoma sordida, locally known as "vinchuca".

Risk is present in rural areas of the following states: Alagoas, Bahia, Ceará, Espírito Santo, Goias, Maranhão, Mato Grosso do Sul, Minas Gerais, Paraíba, Paraná, Pernambuco, Piauí, Rio de Janeiro, Rio Grande do Norte, Rio Grande do Sul, São Paulo, Sergipe and the Federal District. New foci of human infection have recently been reported from the state of Pará. Vectors and wild animal reservoirs are present throughout Brazil.

Main vectors: Panstrongylus megistus, Triatoma brasiliensis, Triatoma infestans, Triatoma sordida. The insects are locally known as "barbeiros".

Chagas'disease has been highly endemic in rural and suburban areas of the following northern and central regions: Tarapacá, Antofagasta, Atacama, Coquimbo, Valparaíso, Santiago and O'Higgins; but national insecticidal spraying campaigns during the last decade have reduced, the house infestation rates by the vector between 80 to 95% of the original rates by 1993. It is hoped that by 1996 the entire country will be free of insect transmission of the disease. Transmission through blood transfusions is under control thanks to compulsory blood screening.

Main vector: Triatoma infestans.

Risk is present in rural areas below 2500 m in the following departments: Boyacá, Caquetá, Cesar, Cundinamarca, Guajira, Huila, Magdalena, Meta, Santander del Norte, Santander del Sur, Tolima, Valle de Cauca.

Main vectors: Rhodnius prolixus, Triatoma dimidiata.

Risk is present in rural areas below 1300 m along the Pacific coast and in the central plain. Guanacaste province reports the highest incidence rates.

Main vector: Triatoma dimidiata.

Risk is present in rural areas throughout Ecuador. Risk is highest in the coastal provinces including urban areas: Esmeraldas, Guayas, El Oro, Los Ríos and Manabi.

Main vector: Triatoma dimidiata.

Chagas'disease is endemic throughout El Salvador. Risk is present in rural areas, small and medium sized towns and suburbs.

Main vectors: Triatoma dimidiata, Rhodnius prolixus.

Risk is present in all rural areas.

Main vector: Rhodnius prolixus.

Risk is present in rural areas below 1500 m of the following departments: Alta Verapaz, Baja Verapaz, Chiquimula, El Progreso, Escuintla, Guatemala, Huehuetenango, Jalapa, Jutiapa, San Marcos, Santa Rosa, Zacapa.

Main vectors: Triatoma dimidiata, Rhodnius prolixus.

The vector Rhodnius prolixus is present in rural areas, but due to the lack of investigations on Chagas'disease the extent of human infection cannot be determined.

Main vector: Rhodnius prolixus.

Risk is present in rural areas below 1500 m in the following departments: Choletuca, Comayagua, Copán, El Paraíso, Francisco Morazan, Intibuca, La Paz, Lempira, Ocotepeque, Olancho, Santa Barbara, Yoro.

Main vectors: Triatoma dimidiata, Rhodnius prolixus.

Risk is present in rural areas below 1500 m in the following states:
Pacific Coast: Sonora, Sinaloa, Nayarit, Jalisco, Colima, Michoacán, Guerrero, Oaxaca, Chiapas.
Gulf of Mexico and Caribbean coast: Veracruz, Tabasco, Campeche, Yucatán, Quintana Roo.
Central Mexico: Durango, Zacatecas, Guanajuata, Hidalgo, San Luis Potosí, México, Morelos, Puebla.

Main vectors: Triatoma dimidiata is present in all infected areas; Rhodnius prolixus is present in Oaxaca and Chiapas.

Risk is present in rural areas below 1500 m in the following departments: Chinandega, Estelí, Jinotega, Léon, Madriz, Managua, Masaya, Matagalpa, Nueva Segovia, Rivas.

Main vectors: Triatoma dimidiata, Rhodnius prolixus.

Risk is present in the rural areas of the provinces of Chiriqui, Bocas del Toro, Coclé, Colón, Darién and Panamá. The highest incidence rates have been reported from Chiriqui, the valley of Río Chagres and the areas of the Canal Zone adjacent to the Río Chagres.

Main vectors: Triatoma dimidiata, Rhodnius pallescens.

Chagas'disease is highly endemic in all rural areas, with particularly high human incidence rates in the Chaco regions.

Main vectors: Triatoma infestans, Triatoma sordida. The insects are locally known as "chincha timbuku" or "chincha guasu".

Risk is present in two separate geographical areas:

1) Rural and suburban areas of the departments of Tumbes, Piura, Cajamarca,Amazonas and Loreto in the northern part of the country bordering Ecuador, with foci in eastern Loreto in the areas of Javary and Amazon rivers bordering Brazil.

Main vector: Triatoma dimidiata.

2) In the southern half of the country in areas below 3500 m, particularly in the rural and suburban areas of the following coastal departments: Arequipa, Ica, Moquegua, Tacna.

Main vector: Triatoma infestans, locally known as "vinchuca" or "chirimacha".

The vector Rhodnius prolixus is present in rural areas, but due to the lack of investigations on Chagas' disease the extent of the infection is undetermined.

Chagas'disease, once endemic, is on the verge of being completely eradicated in Uruguay thanks to continuous nationwide surveyance and insecticidal spraying programs. Transmission through blood transfusions is no longer a problem.

Main vector: Triatoma infestans, locally known as "vinchuca".

Risk is present throughout rural areas, except the southern parts of Amazonas and Bolívar.

Main vectors: Rhodnius prolixus, Triatoma maculata, locally known as "vinchuca".

IAMAT acknowledges the assistance provided by the Oswaldo Cruz Institute, Rio de Janeiro, the Tropical Medicine Institute of Caracas, the Ministries of Health of Argentina, Bolivia, Brazil, Paraguay, Peru, Venezuela, and the WHO, Geneva.