Chagas Disease – Devolution in the Tropics

Chagas’ disease is a human tropical parasitic disease which occurs in the Americas, particularly in South America (see map below). It is transmitted to humans and other mammals mostly by blood-sucking assassin bugs (Trypanosoma cruzi). Other methods of transmission are possible, such as ingestion of food contaminated with parasites, blood transfusion and fetal transmission. 

Trypanosoma cruzi is a member of the same genus as the infectious agent of African sleeping sickness and the same order as the infectious agent of leishmaniasis, but its clinical manifestations, geographical distribution, life cycle and insect vectors are quite different.


The symptoms of Chagas’ disease vary over the course of the infection. In the early, acute stage symptoms are mild and are usually no more than local swelling at the site of infection. As the disease progresses, over as much as twenty years, the serious chronic symptoms appear, such as heart disease and malformation of the intestines. If untreated, the chronic disease is often fatal. Current drug treatments for this disease are generally unsatisfactory, with the available drugs being highly toxic and often ineffective, particularly in the chronic stage of the disease.


The disease was named after the Brazilian 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 (the outbreak of Chagas’ disease in Brazil in the 1920s went widely ignored).

Chagas’ work is unique in the history of medicine because he was the only researcher so far to describe solely and completely a new infectious disease: its pathogen, vector, host, clinical manifestations, and epidemiology. Nevertheless, he believed (falsely) until 1925 that the main infection route is by the bite of the insect – and not by its feces, as was proposed by his colleague Emile Brumpt in 1915.

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. 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.

Alternative Infection Route

Researchers suspected since 1991 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 Amazonia (17 such episodes recorded between 1968 and 1997). In 1991, farm workers in the state of Paraíba, Brazil, were apparently infected by contamination of food with opossum feces; and in 1997, in Macapá, state of Amapá, 17 members of two families were probably infected by drinking açaí palm fruit juice contaminated with crushed triatomine vector insects. In the beginning of 2005, a new outbreak with 27 cases was detected in Amapá. Despite many warnings in the press and by health authorities, this source of infection continues unabated. In August 2007 the Ministry of Health released the information that in the previous one year and half 15 clusters of Chagas infection in 116 people via ingestion of açaí have been detected in the Amazon region.

In March 2005, a new startling outbreak was recorded in the state of Santa Catarina, Brazil, that seemed to confirm this alternative mechanism of transmission. Several people in Santa Catarina who had ingested garapa (sugar cane juice) by a roadside kiosk acquired Chagas’ disease.