PROTOMONADINA 349 



far north as Mexico in North America. In the infected person, the 

 heart and skeletal muscles show minute cyst-like bodies. 



The transmission of the organism is carried on apparently by nu- 

 merous species of reduviid bugs, bed bugs and certain ticks, though 

 the first named bugs belonging to genus Triatoma (cone-nosed or 

 kissing bugs) especially T. megista (Panslrongylus megistus), are the 

 chief vectors. When P. megistus (nymph or adult) ingests the in- 

 fected blood, the organisms undergo division in the stomach and 

 intestine, and become transformed into crithidia forms which con- 

 tinue to multiply. In eight to 10 days the metacyclic or infective 

 trypanosomes make their appearance in the rectal region and pass 

 out in the faeces of the bug at the time of feeding on host. The para- 

 sites gain entrance to the circulatory system when the victim 

 scratches the bite-site or through the mucous membrane of the eye 

 (Brumpt, 1912; Denecke and von Haller, 1939; Weinstein and Pratt, 

 1948). 



Cats, dogs, opossums, monkeys, 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 

 fuscipes 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 (Mus 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. In fact, the organisms from a naturally infected Triatoma 

 heidemanni were shown by Packchanian (1943) to give rise to a 

 typical Chagas' disease in a volunteer. Reduviid bugs (Usinger, 

 1944) ; Chagas' disease in the United States (Packchanian, 1950) ; in 

 central Brazil (Dias, 1949). 



T.brucei Plimmer and Bradford (Fig. 145, a). Polymorphic; 

 15-30ju long (average 20/x); 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, 

 camels, cattle, swine, dogs, etc., which terminates in the death of 



