PROTOMONADINA 277 



later into trypanosomes which, through rupture of host cells, become 

 liberated into blood stream. 



This trypanosome is the causative organism of Chagas' disease or 

 South American trypanosomiasis which is mainly a children's dis- 

 ease, and is widely distributed in Brazil, Argentina, Uruguay, 

 Peru, Venezuela, Colombia, Panama, Salvador, Guatemala, and 

 Mexico. In the infected person, the heart and skeletal muscles show 

 cyst-like bodies. 



The transmission of the organism is carried on by numerous spe- 

 cies of reduviid bugs, bed bugs and certain ticks, though the first 

 named bugs belonging to genus Triatoma (cone-nosed or kissing 

 bug), especially T. megista, are the chief vectors. When T. niegista 

 (nymph or adult) ingests the infected blood, the organisms undergo 

 division in stomach and intestine, and become transformed into 

 crithidia forms which continue to multiply. In 8-10 days the meta- 

 cyclic or infective trypanosomes make their appearance and pass out 

 in the faeces of the bug. Inoculation of the parasite into man appears 

 to take place through ingestion of the insect faeces or scratching the 

 bite-site and directly injecting the trypanosomes into the wounds. 



Cats, dogs, opossums, monke3^s, armadillos, bats, foxes, squirrels, 

 wood rats, etc., have been found to be naturally infected by T. cruzi, 

 and are considered as reservoir hosts. Vectors are also numerous. 



No cases of Chagas' disease have been reported from the United 

 States, but Wood (1934) found a San Diego wood rat (Neotoma 

 fiiscipes macrotis) in the vicinity of San Diego, California, in- 

 fected by Trypanosoma cruzi and Packchanian (1942) observed in 

 Texas, 1 nine-banded armadillo (Dasypis novemcinctus) , 8 opossums 

 (Didelphys virginiana), 2 house mice {AIus musculus), and 32 wood 

 rats (Neotoma micropus micropus), naturally infected by Trypano- 

 soma cruzi. It has now become known through the studies of Kofoid, 

 Wood, and others that Triatoma protracta (California, New Mex- 

 ico), T. rubida (Arizona, Texas), T. gerstaeckeri (Texas), T. heide- 

 manni (Texas), T. longipes (Arizona), etc., are naturally infected 

 by T. cruzi. Wood and Wood (1941) consider it probable that 

 human cases of Chagas' disease may exist in southwestern United 

 States. For information on the species of Triatoma and their re- 

 lationships to Trypanosoma cruzi, the reader is referred to Usinger 

 (1944). 



T. hrucei Plimmer and Bradford (Figs. 9, a; 124, a). Polymorphic; 

 15-30/i long (average 20fx); transmitted by various species of tsetse 

 flies, Glossina; the most virulent of all trypanosomes; the cause of 

 the fatal disease known as "nagana" among mules, donkeys, horses, 



