American Trypanosomiasis 521 



rounded form, and by schizogony give rise to a great number of 

 daughter parasites, each having a nucleus and a blepharoplast. 

 For a time the schizonts are quiescent, then develop flagellae and 

 undulating membranes. The infected cells are destroyed. Chagas 

 thmks that gametes are formed only in the lungs. 



In the definitive host, the Lamus (or Conorhinus) megistis, the 

 sexual conjugation occurs in the mid-gut. The blepharoplast 

 approaches and seems to blend with the nucleus, the undulating 

 membrane disappears and the parasites assume a spherical form. 

 Actual conjugation does not seem to have been observed. Multi- 

 plication takes place by division of these rounded organisms, the 

 daughter parasites becoming flagellated, the flagellum originating 

 from the blepharoplast. Numerous flagellated trypanosome and 

 crithidia forms of the parasite are observed in the hind-gut of the 

 insect. Chagas observed trypanosome forms in the body cavity 

 and in the salivary glands by the insect, and it is probable that it is 

 through these that the infection is transmitted when the insect 

 bites a susceptible animal, though Brumpt thinks the infection may 

 take place through the feces of the bug, especially when these are in 

 some way brought to the conjunctiva. 



Transmission.^ — Chagas was able to show that a large bug, 

 Lamus (Conorhinus) megistus, common in the neighborhood in 

 which Opliafao occurs, is the principal definitive host of the parasite. 

 Both males and females of this flying bug are vicious biters and both 

 live upon human blood as well as upon the bloods of other warm- 

 blooded vertebrates. The bugs are common in the thatch and in 

 the cracks between the timbers of the native houses. Whether 

 other species of Lamus may also harbor the parasites is not known. 

 Brumpt* found that Cimex lectularius, Cimex boneti and Ornitho- 

 dorus moubata could also act as definitive hosts. A study of 

 Cimex lectularius, the common bed-bug, as a definitive host of the 

 parasite, was made by Blacklockf who found that only a very 

 occasional bug becomes so infected as to be able to effect the 

 transmission. 



Cultivation. — The parasites are easily cultivated in vitro in the 

 medium recommended for trypanosomes by Novy and McNeal. 

 In culture the organisms resemble those found in the bugs, i.e., 

 round and crithidial forms, or pear-shaped rapidly dividing forms. 

 More than two subcultures can rarely be made before the organisms 

 die out. 



Pathogenesis. — The Schizotrypanum is pathogenic for certain 

 monkeys (Callithrix), dogs, rabbits and guinea-pigs. Guinea-pigs 

 usually die in five to ten days, though the trypanosome forms are not 

 usually found in the peripheral blood. They are, however, present 

 in larger numbers in the lungs. Monkeys live longer. Trypano- 



* "Centralbl. f. Bakt. etc. Ref.," lv, No. 3, p. 75. 

 t "British Medical Journal," 1914, i, 912. 



