TRYPANOSOMIDM 



cultivated, and appears to develop in certain flies — for example, Tabanus 

 tropicus, T. lineola, Stomoxys calcitrans, S. geniculaius, in the stomach of the 

 last of which it has been found. Certainly it can be transmitted to healthy 

 animals by the bites of flies and fleas. It is said that it can also be contracted 

 by eating infected meat. 



r. stviatus Fabricius, according to Mitzmain, can mechanically transmit 

 surra. 



Pathogenicity. — The symptoms are fever, remittent or intermittent, emacia- 

 tion, oedema of the limbs and ventral surfaces, frequently lesions of the eyes 

 and eyelids, great muscular weakness,, paralysis, and death. The treatment is 

 by arsenic. A variety, C. evansi var. mborii Laveran, 1905, is the cause of the 

 disease mbori in dromedaries in Africa. 



Gastellanella brucei Plimmer and Bradford, 1889. 



Synonyms. — Perhaps T. equi Blacklock and Yorke, 1913. According to 

 Bruce, T. rhodesiense and T. ugandcB. 



This parasite was discovered by Sir David and Lady Bruce in 1 895 in animals 

 sufEering from the tsetse-fly disease or nagana (which means ' weakness ') in 

 Zululand. At the same time they showed that the tsetse-fly {Glossina mof si- 

 tans) disseminated the disease. 



The parasite is widespread throughout Africa, especially in Zululand, 

 Northern Transvaal, and its surrounding countries; also from Pretoria to 

 Lake Nyassa in the basin of the Limpopo, in the basin of the Zambesi, in 

 East Africa, where it causes nagana or the fly disease, and in Uganda, 

 where it is called ' jinja.' 



Morphology. — The appearance of the parasite is worm-like, being 28 to 33 fjL 

 in length in horses and donkeys. The length is constant for the given animal, 

 but varies in different hosts, being 26 to 27 [jl in rats, mice, guinea-pigs, rabbits, 

 and dogs. The anterior end (non-flagellate) is a truncated cone, behind which 

 lies the kinetonucleus as a well-marked rounded mass, posterior to which the 

 flagellum arises. The trophonucleus lies in the middle of the body, and 

 many chromatoid granules may be seen posterior to it, while still further 

 posterior the free whip of the flagellum may be noted. Koch considers C. 

 brucei to be identical with C. evansi, but the animal reactions clearly show 

 them to be difierent species. 



Life-History. — The life-cycle in the vertebrate host has not been very fully 

 worked out, but the longitudinal division is well known. The kinetonucleus 

 divides first, then the flagellum, then the trophonucleus, and finally the 

 cytoplasm, but, according to Prowazek, division is really a very complicated 

 process. First the blepharoplast becomes thickened, elongated, and dumb- 

 bell-shaped, and then divides. In the trophonucleus the chromosomes behave 

 like the kinetonucleus and the centrosome, and, having divided, the whole 

 nucleus divides. The chromatin granules in the cytoplasm are also said to 

 undergo fission, while a new flagellum develops from the new kinetonucleus. 

 Parasites resembling the latent forms of Breinl and Hindle are known, and are 

 called involution forms. 



It is believed by some authorities that the parasite lives in nature in the 

 wildebeeste {Catoblepus gnu) , the koodoo [Strepsiceros capensis), the bush-buck 

 [Tragelaphus scriptus sylvaticus), and the hyena, without causing disease. 

 These may form a reserve from which the tsetse- flies G. morsitans, G. pallidipes , 

 and G. fusca can obtain parasites which undergo development in their alimen- 

 tary canal, during which time they are non-pathogenic, and when fully 

 developed are found in the proboscis, and are again capable of being inoculated 

 into animals, in some of which they are pathogenic. Kleine has proved that 

 the transmission of the trypanosome is not merely mechanical, as suggested 

 by Bruce and others, but also takes place after the tr5rpanosome has undergone 

 development in the fly, which is its true host. Thus, freshly caught G. morsi- 

 tans for the first three days infected cattle, and then, from the fourth to the 

 tenth day the flies were non-infective, but from the eleventh to the forty- 

 fourth day they were very infective. This shows that the parasite must 

 undergo a development in the fly. 



