Natural history of Chagas' disease
T. cruzi populations include multiclonal strains with different biological properties such as replication rates, drug susceptibility, virulence, and tissue tropism, which may be implicated in the clinical forms of the disease.10,11 T. cruzi is an obligate
intracellular parasite. Among immunocompetent individuals the clinical course of Chagas’ disease is usually divided into three stages: acute, indeterminate, and chronic. The indeterminate phase usually extends 10—20 years, but in the majority of the patients it lasts a lifetime.12,13 As well as in immunocompromised patients, in some subjects, during the acute phase of the disease, it is probable to show signs and symptoms associated with parasitemia (Fig. 30.1). These patients can present clinical manifestations of acute myocarditis or meningoencephalitis.14—16 When T. cruzi invade the myocardial cells it induces a diffuse and severe neutrophilic and monocytic inflammatory infiltrate and myofibrillar lesions with or without fibrosis that can be seen in endomyocardial biopsies. Also, during the acute phase of the disease, cardiac parasympathetic neurons are damaged by the parasite.17 Meningoencephalitis occurs mainly in acute Chagas’ disease in children under 2 years. After the acute phase, the majority of cases progress to a subclinical and latent period named as the indeterminate phase.18,19 Finally, 10—30% of seropositive individuals developed three different syndromes in the context of symptomatic chronic Chagas’ disease. These are the chronic cardiomyopathy with frequent and marked cardiac arrhythmias, especially sinus bradycardia with right bundle branch block and other electrocardiographic abnormalities. In other patients, the destruction of visceral autonomic neurons of the digestive tract leads to progressive enlargement of visceral organs (especially megaesophagus and megacolon) named as megasyndromes or chronic gastrointestinal Chagas’ disease. Megaesophagus and
Figure 30.1 Natural history of HIV and Chagas’ disease coinfection.
Source: Taken from DiazGranados CA, Saavedra-Trujillo CH, Mantilla M, Valderrame S, Alquichire C, Franco-Paredes C. Chagasic encephalitis in HIV patients: common presentation of an evolving epidemiological and clinical association. Lancet Infect Dis 2009;9:324—30.14
megacolon may or may not be associated with the cardiac involvement and occur in 10 to 20% of cases according to the area considered.20,21 A small number of patients develop different grades of neuropsychiatric compromise.
