94 THE ANIMAL PARASITES OF MAN 



The virus is maintained in nature in certain big game, such as wilde- 

 beest, bushbuck and koodoo, which thus act as living reservoirs of 

 disease from which the tsetse may become infected. These reservoir 

 hosts are not injured, apparently, by the presence of the parasites. 



T. brucei is rapidly fatal to the small laboratory animals, such as 

 rats and mice. Horses, asses and dogs practically always succumb 

 to its attacks, while a very small number of cattle recover from 

 " nagana." The disease is characterized by fever, destruction of red 

 blood corpuscles, severe emaciation and by an infiltration of coagu- 

 lated lymph in the subcutaneous tissue of the 

 neck, abdomen and extremities giving a swollen 

 appearance thereto. The natural reservoirs in 

 which T. brucei has been long acclimatized are 

 unaffected by the trypanosomes, while the newer 

 hosts, such as imported cattle in Africa, are 

 rapidly destroyed by their action. 



The general morphology and life history in 

 the vertebrate host is that of a typical trypano- 

 some (fig. 40). Its length is from 12 //, to 35 yu,, 

 its breadth from 1*5 //, to 4/4. Multiplication by 

 longitudinal division proceeds in the peripheral 

 blood (fig. 26), while latent, leishmaniform 

 FIG. qz. Trypanosoma bodies are produced in the internal organs. 



[Tveran and'Z^il.t"' Bruce and colleagues' have quite recently 



(June, 1914) described the development of a 



Zululand strain of T. brucei in G. morsitans. The tsetse flies were 

 bred out in Nyasaland. In vertebrate blood the brucei strain 

 was polymorphic. The development was like that found for 

 T. gambiense in G. palpalis (fig. 30), and by Bruce and colleagues for 

 T. rhodesiense in G. morsitans in Nyasaland. Long trypanosomes 

 were found in the proventriculus of the tsetse. Crithidial, rounded 

 or encysted, and immature " blood forms " occurred in the salivary 

 glands; and finally infective, stumpy, "blood forms " were differen- 

 tiated in the salivary glands. The period of development of T. brucei 

 in G. morsitans takes about three weeks, and then the fly becomes 

 infective. Bruce believes that T. rhodesiense of Nyasaland and 

 T. brucei of Zululand are the same, their cycles of development 

 in G. morsitans being " marvellously alike." (But see Laveran, p. 80.) 



T. brucei has been cultivated with difficulty by Novy and MacNeal, 

 using blood agar. The best treatment for nagana is arsenic in some form. 



It is probable that more than one trypanosome has been con- 

 fused under the name T. brucei, more especially as the occurrence of 

 many species of trypanosomes in various animals in Africa was not 



1 Proc. Roy. Soc.> B ; Ixxxvii, p. 526. 



