The Blood Flagellates 593 



sometimes an acute myocarditis which may lead to heart failure. Mortality 

 in this form of Chagas' disease often exceeds 10 per cent. 



The acute form of the disease runs a fairly short course. In surviving 

 patients, the trypanosomes usually disappear from the blood after a few 

 weeks and the oedema and other symptoms gradually subside. The 

 temperature often drops to normal. However, a low fever may persist 

 for some time after termination of the acute phase. Although there may 

 appear to be clinical recovery, the infection may persist, even for as 

 long as 16 years (22). In other words, a patient may simply progress from 

 the acute into the chronic form of the disease. 



The usual chronic case is the cardiac type and, for practical purposes, 

 almost every chronic case may be considered a potential heart patient. 

 Symptoms vary with the extent of damage to cardiac muscle. While 

 myocardial damage is progressive, it is usually so slow that several years 

 may be required to produce indications of heart failure. Symptoms may 

 be mild or almost unnoticeable, the only evidence of cardiac damage 

 being that obtained with the electrocardiograph. Commonly, however, 

 such symptoms as dyspnea, palpitation, and abdominal pain in the 

 upper right quadrant are observed. Cardiac enlargement is often notice- 

 able, and irregularities in heart rhythm are common. Prognosis of the 

 cardiac case depends upon progress of the infection. Patients with slight 

 or moderate enlargement of the heart may be expected to live for several 

 years. For those with marked enlargement, the outlook is rather un- 

 certain. Mortality in chronic cases approaches 10 per cent, and the 

 majority of deaths occur before the age of fifty. 



Pathological effects include degeneration of the invaded cells as well 

 as a cellular infiltration and eventual fibrosis of the invaded tissues. 

 Lesions of the heart, brain and liver are most characteristic, although the 

 flagellates have been found in most organs of the body in acute cases. 

 The heart shows a diffuse myocarditis. Among the muscle fibres there 

 is extensive infiltration of lymphocytes and macrophages, sometimes with 

 wide separation of the individual fibres, some of which show fragmenta- 

 tion and degeneration. Groups of leishmanial forms may be found either 

 in the muscle fibres or in large mononuclear cells and monocytes. Cellular 

 infiltration of the epicardium and endocardium is noted occasionally. 

 Multiplication of T. cruzi may also occur in skeletal muscle, which shows 

 much the same changes as cardiac muscle. Damage to the brain is ob- 

 served in some cases. Parasites may be found in neuroglia cells and 

 in large mononuclears in centers of inflammation scattered through the 

 nervous tissue. In the liver, the flagellates have been found in Kiipffer 

 cells. Fatty degeneration of liver tissue is sometimes noticeable and en- 

 largement of the liver is fairly common. The spleen also may be enlarged 

 to some extent, but parasites have been detected less commonly than 

 in the liver. Leishmanial stages also have been found occasionally in the 



