Tropical Medicine Mission Index of Diseases About Tropical Medicine Tropical Medicine Home Page Tropical Medicine Staff

Next Page

Chronic Chagas' Myocardiopathy (CCM)

Symptoms of acute Chagas' disease last only a few months in most patients, although about 15% of these seemingly recovered individuals will have an abnormal EKG. In any endemic area, the majority will be asymptomatic with latent or chronic trypanosomiasis.

Cardiac disease in these patients usually develops slowly over 10-20 years, during which time the patients remain asymptomatic. During this period the number with an abnormal EKG will increase, until in some populations 50% will have myocardial damage. The majority (82%) will be 11-50 years of age, with the highest incidence in the third and fourth decades. There is a slight male predominance. These statistics vary in different parts of South America. In Argentina, for example, 2.5 million people are infected with T. cruzi and over 18% have chronic myocarditis; it is likely that 20% of these patients will die within 2 years of the diagnosis. In the rural areas of Venezuela in 1958, there were over half a million infected persons, of whom 50% had EKG abnormalities.

The pathogenesis of Chagas' cardiomegaly is controversial. It is generally accepted that the disease represents a chronic myocarditis caused by T. cruzi. However, for each myocardial fiber containing parasites there are thousands of damaged or destroyed fibers without amastigotes and this raises other hypotheses. The parasites may destroy myofibers indirectly by elaboration of a toxic substance or by an immunological mechanism; autoimmune destruction is suspected by many investigators since T. cruzi shares common antigens with cardiac myofibrils.

However, a recent study by Tarleton et al suggests that heart damage, and resulting sudden death, is due not to the body's immune response to heart tissue but rather to an immune reaction to the parasites within the heart itself despite the difficulty in finding T. cruzi there. They believe their data indicate the parasite load should be reduced in patients to prevent chronic disease progression, whereas currently victims of Chagas' disease usually are not treated for parasite eradication after the acute phase, chiefly because physicians have thought the body's alleged autoimmune reponse would be difficult or impossible to treat. Despite millions of people infected or at risk, there is presently no vaccine development in progress, principally because of the engrained concept of an autoimmune origin for the disease. Tarleton believes that "even if autoimmunity is a component of the disease, we cannot treat this as an autoimmune disease. We must treat it as a parasitic disease. We must develop protocols to clear the parasites. If we do that, we can get rid of the disease."

Back to the Table of Contents

Copyright: Palmer and Reeder