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Memórias do Instituto Oswaldo Cruz
On-line version ISSN 1678-8060
ANDRADE, Zilton A. and ANDRADE, Sonia G.. A patologia da doença de Chagas experimental no cão. Mem. Inst. Oswaldo Cruz [online]. 1980, vol.75, n.3-4, pp. 77-95. ISSN 1678-8060. http://dx.doi.org/10.1590/S0074-02761980000200008.
Young dogs experimentally infected with Trypanosoma cruzi developed acute disease and were studied by pathologic, immunologic, parasitologic and eletrocardiographic methods. The main lesion was an acute myocarditis that began in the atria and propagated through the septum toward the ventricles and, when fully developed, predominated in the right atrium, the right half of the ventricular septum and the free wall of the right ventricle. ECG changes were progressive and reflected the predominant atrial involvement. Cardiac blocks appeared only at the terminal stages and coincided with severe inflammation and necrosis along the A-V conducting tissue. Specific treatment made in 15 dogs with severe acute disease frequently reversed both the histological and ECG changes. Ten animals went into a chronic asymptomatic stage of the infection, three of them after being treated, and were observed from periods of 8 months to 3 years. None of them developed signs of congestive cardiac failure. ECG changes were both non-specific and transient. However, there were focal areas of fibrosis, sclero-atrophy and fatty replacement within the conducting tissue of the heart, probably sequelae from the lesions occuring during the acute infection. There were focal and mild myocarditis in some of the cases. The chronic cardiac form of the disease was studied in microscopic slides from one typical case. This dog developed chronic progressive cardiac failure and complete right bundle branch block 18 months after inoculation. There were cardiomegaly and chronic progressive diffuse myocarditis with fibrosis. Thus, the canine model of Chagas' disease present all stages of the infection as seen in man. Digestive megas were not seen in the present material, but have been described by others. The experimental reproduction of the symptomatic chronic forms in the dog are unpredictable. The present paper aims at presenting the fundamental aspects of the pathology of Chagas's disease in the dog, which are necessary for future studies with the canine model.