Clinical and epidemiological aspects of Chagas disease.

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi. During the past decades, after urban migrations, Chagas disease became frequent in cities and a health problem in non-endemic countries, where it can be transmitted vertically and by blood transfusion or organ transplantation. Microepidemics of acute Chagas disease have been reported, probably due to oral transmission. Heart involvement is the major feature of the disease because of its characteristics, frequency, and consequences, and is also the source of most controversies. The indeterminate clinical form, despite its good prognosis on at least a medium-term basis (5-10 years), has acquired increasing importance due to the controversial meaning of the abnormality of some tests and the myocardial focal lesions found in many patients. Simultaneous evaluation of the parasympathetic and of the sympathetic system in the heart has been done by spectral analysis of heart rate. The physiopathological and clinical significance of denervation in Chagas disease is still incompletely understood. There are major divergences of opinion on specific treatment during the chronic phase because of the doubts about cure rates. Changes of Chagas disease prevalence in many countries have been certified by the Pan American Health Organization, and are ascribed to large-scale vector-control programmes with modern pyrethroid insecticides and to improvement in lifestyle.