The disease is caused by the pathogenic hemoflagellate [Trypanosoma cruzi], and is transmitted to man by blood-sucking insects (triatomid bugs) from the forest and fields in or near human dwellings. There, they breed and feed, transmitting the disease. Domestic animals, such as cats, dogs and guinea pigs, and humans in rural areas and in slums become infected by contamination of the bite wound with the insects' faeces, which are infected with the invasive trypanosomes. Transmission by blood transfusion may also occur where no prevention measures exist.
The acute form of Chagas disease occurs predominantly in young children and is characterized by fever, adenopathy, spleen and liver enlargements, and in some forms facial oedema. The brain is often affected and convulsions may result in permanent mental damage or even in death. The chronic form may be mild, but cardiopathy due to parasite development in the heart muscles may be extremely serious, provoking in some cases sudden death from heart failure.
The economic harm caused by the disease is considerable. In the first place, the incapacitating symptoms of the chronic forms of the disease generally develop in the second half of life when the individual is making his greatest contribution to society. Secondly, the disease is found principally in rural areas where those affected are often rendered incapable of the heavy physical work demanded of them. Equally costly is the hospitalization and subsequent rehabilitation of patients with Chagas disease.
The risk is greatest for the rural poor. The insect vectors of Chagas' disease are endemic to nearby fields and forests and naturally infest dwellings constructed of conventional mud wattle, substandard cement, and thatched roofs, living in the cracks between the construction materials. Futhermore, traditional construction methods foster a lack of natural interior light and poor ventilation, factors that maintain the dark and humid conditions that are favourable to these insects. One solution would have houses periodically sprayed with insecticides. This is an expensive intervention, using imported chemicals, which are costly, often a health risk, and usually cannot be sustained or replicated in developing countries. The endemic nature of the insects ensures that reinfestation will occur as soon as the pesticide has lost its effectiveness (usually over the course of one year).