154 



DISEASES DUE TO PROTOZOA 



SOUTH AMERICAN TRYPANOSOMIASIS. 



HISTORY, &c. 



This disease is caused by Trypanosoma cruzi discovered by 

 Chagas in 1909. 



It is spread by the bug Lamus megistus and alHed forms. 



Its reservoir is probably in the Armadillo, Dasypus novemcinctus. 



The bugs live in the burrows of the armadillo. 



The disease is only known amongst the poorer inhabitants of the 

 State of Minas in Brazil where it appears to attack the whole 

 population. 



iETIOLOGY. 



The Trypanosoma cruzi has a large kineto nucleus. 

 It is found in domestic animals and man. 



Trypanosoma cruzi. Schizogony. /, merozoite in rei blood corpuscle ; 2, parasite 

 totally enclosed in red cell, no flagellum or undulating membrane ; j-j", parasites partially 

 enclosed in red cell ; 6, 7, parasites in human blood ; Sir, parasites in lungs of the monkey, 

 Callithrix ; 12, ij, initial forms of schizogony ; 14, /j, schizogony in the lungs of Callithrix. 

 (After Chagas.) 



Three forms of the trypanosome are seen in man : — 

 (i) With a large nucleus, loose chromatin and a terminal kineto 

 nucleus. 



(2) A narrower form with an oval nucleus and dense chromatin. 



(3) A form with an elongated nucleus. 



The trypanosome undergoes multiplication in one of three ways : — 

 (i) Schizogony . — This takes place in the capillaries of the lungs 

 of the callithrix where it loses its flagellum and undulating membrane, 

 it curves itself and forms a disc which divides into eight merozoites. 

 These enter the red cells and become adult trypanosomes. Later 

 they leave the red cells and live free in the blood-stream. Schizogony 

 probably differentiates sexual forms and lays the basis for infection 

 of invertebrate hosts. 



