CHAGAS' DISEASE — PARASITE IN MAN 



109 



bugs of the genus Triatoma serve as intermediate hosts; bugs of 

 a number of species infected with trypanosomes morphologically 

 indistinguishable from T. cruzi have been found all the way from 

 Central America to Argentina, but the disease in man has been 

 recognized only in 

 a small part of 

 this extensive area, 

 though it is sus- 

 pected of existing 

 in northern Argen- 

 tina and may oc- 

 cur in many more 

 places than is now 

 known. 



Human Cycle. — 

 The trypanosome 

 causing this disease 

 very closely resem- 

 bles the sleeping 

 sickness trypano- 

 somes in form but 

 it is quite different 

 in its life history. 

 In the humanbody, 

 Chagas recognized 

 two distinct types 

 which he believed 

 to be male and fe- 

 male forms, but 

 subsequent work 

 indicates that these 

 two types are 



merely young and capillary; unpar. c, unparasitized cells. X 1000. (After 



adult forms of the 



parasite. Unlike other trypanosomes this species as found in 

 the blood never exhibits stages in division, and this fact led 

 Chagas to search for some other form of multiplication. He 

 found in the lungs of infected animals what he thought to be 

 a process of division of the trypanosomes into eight parts, but 

 this later was found to be a stage in the life history of an entirely 



Fig. 26. Trypanosoma cruzi. ^, cyst containing Lcisfe- 

 mania forms in muscle fiber of guinea-pig, cross section; 

 n., nucleus of muscle fiber. B, older cyst, containing 

 trypanosome forms, in neuroglia cell in gray matter of 

 cerebrum; n., nucleus of parasitized cell; bl. cap., blood 



