TRYPANOSOME GAMBIENSE 489 



game may act as reservoirs of the parasite, and it has 

 been seriously suggested to kill off all the big game in 

 the affected areas. It is conveyed by a tsetse-fly (G. 

 palpalis), possibly by other tsetses. 



The tsetse (and possibly other biting flies) may rarely convey 

 the disease by direct inoculation. Generally a cycle of development 

 is passed in the tsetse. The stages of this are not known with 

 certainty, but Roubaud has observed multiplication of the parasites 

 in the fly and the development of Herpetomonas forms. According 

 to the observations of Kleine and Bruce, the flies become infective 

 about thirty-four days after feeding and remain infective for at 

 least 70-80 days, and probably for the rest of their lives. 



In Rhodesia, a human trypanosome (Tr. Khodesiense) has been 

 found which is probably distinct from Tr. gambiense, and the 

 O. palpalis does not occur in the district. The macronucleus of the 

 parasite is situated between the blepharoplast and the posterior end. 



In Brazil another human trypanosome-like parasite has been 

 discovered by Chagas (Tr. or Schizotrypanum cruzi), which is 

 conveyed by a bug (Conorhinus megistus). 



Tr. Brucei is the causative parasite of nagana or tsetse- 

 fly disease of horses in Africa. 



Nagana is met with in large tracts of country in Zululand 

 and West Africa. It especially attacks the equines 

 horse, mule, and ass in which it is very fatal. The 

 animals become anaemic and emaciated, there is a discharge 

 from the eyes and nose, staring coat, swelling of the legs 

 and neck, and fever. The animal dies two to six weeks 

 after infection. Oxen are also attacked, but a small 

 proportion recover. The dog, cat, rabbit, guinea-pig, 

 mouse, and rat may be infected by inoculation with the 

 fresh blood of a diseased animal. In infected animals 

 the trypanosome is generally abundant in the blood and 

 spleen. The Tr. Brucei can be cultivated, though with 

 difficulty, on rabbit-blood agar melted sterile agar cooled 

 to 45 C. -f sterile defibrinated rabbit's blood warmed to 

 45 C., mixed and allowed to solidify in the sloping position 

 (Novy and McNeal). The disease is conveyed through the 



