594 The Blood Flagellates 



thyroid, adrenal glands, ovaries, and testes. Enlargement and congestion 

 of lymph glands are common effects but the flagellates seem to be absent 

 or rarely present in lymphatic tissue. 



Diagnosis. Microscopic detection of T. cruzi is often easy enough in the 

 early acute stage. In addition, the precipitin test is useful in diagnosis 

 of early cases with mild symptoms (43a). In chronic cases, flagellates occur 

 in the blood in small numbers at most and the examination of blood 

 smears is usually negative. Culture methods have been used, and their 

 practical value may be increased by the addition of bacteriostatic agents 

 (penicillin, streptomycin) to suitable media (58a). Inoculation of blood 

 into laboratory animals may give good results, and xenodiagnosis also 

 is often effective. In xenodiagnosis, trypanosome-free insects are allowed 

 to feed upon suspected human cases. The subsequent appearance of 

 T. cruzi in the triatomids justifies a positive diagnosis. The success of 

 xenodiagnosis depends upon an adequate number of trypanosomes in 

 the blood, and some workers feel that the results are positive in an 

 unfortunately small percentage of chronic cases. Precipitin tests appar- 

 ently have little value in chronic cases (43a), but accurate diagnosis is 

 possible with complement-fixation tests (Machado-Guerreiro reaction) in 

 which the test antigen is prepared from cultures of T. cruzi (Chapter 

 XIV). Results already obtained in thousands of tests (18, 23, 45, 50) sug- 

 gest that complement-fixation is superior to other diagnostic procedures 

 and should be the method of choice for suspected chronic cases. 



Therapy and control. Chemotherapy has been generally ineffective 

 and the problems of treatment are complicated by the usual occurrence 

 of the most acute cases in young children. A quinaldine compound, 

 Bayer 7602 Ac, is one of the few which have shown some activity against 

 T. cruzi. The drug has been tried in acute cases, but the results are 

 scarcely extensive enough for accurate evaluation. General methods of 

 treatment are those used for heart patients — rest, dietary control, and 

 other methods indicated for relief of heart failure. 



Control of Chagas' disease is essentially an economic problem. Preva- 

 lence of the disease in rural areas of Central and South America is 

 mainly attributable to the infestation of native cabins and huts with 

 triatomid bugs. Long range control must depend upon improvements 

 in rural housing, since well built houses with adequate screening are 

 effective barriers to the vectors. In short-term control, the persistent use 

 of insecticides, although only an emergency measure at best, can be 

 reasonably effective on a limited scale. 



LITERATURE CITED 



1. Acton, H. W. and L. E. Napier 1927. Inch J. Med. Res. 15: 97. 



2. Adler, S. 1940. Mem. Inst. Oswaldo Cruz 35: 179. 



3. and M. Ber 1941. Ind. J. Med. Res. 29: 803. 



4. and O. Theodor 1927. Ann. Trop. Med. & Parasitol. 21: 89. 



5. and 1929. Trans. Roy. Soc. Trop. Med. & Hyg. 22: 343. 



