THE HEMOFLAGELLATES 



51 



epidemiologic differences between them 

 make it more convenient to retain separ- 

 ate names. Whatever the names used, it 

 is clear that these species arose from 

 strains of T. brucei which became adapted 

 to man. 



Human trypanosomosis occurs in 

 tropical Africa, roughly between 15° N 

 and 15° S latitude. T. yliodesiense, which 

 causes an acute form of the disease, 

 occurs in Rhodesia, Tanganyika, Nyasa- 

 land, Bechuanaland and Portuguese East 

 Africa, while T. gambiense, which causes 

 a chronic form of the disease, occurs in 

 a large part of the remainder of the area. 

 Kunert (1953) prepared a map of the dis- 

 tribution of human sleeping sickness in 

 Africa together with climatologic and 

 other information. Ashcroft (1959a) and 

 Morris (1960) reviewed its epidemiology. 



In general, T. gambiense causes a 

 "domesticated" type of disease, trans- 

 mitted by tsetse flies from man to man in 

 regions of human habitation, while T. 

 rhodesiense causes more of a woodland 

 disease and people become infected with 

 it away from their village areas. 



Altho it is certain that some wild ani- 

 mals must serve as reservoirs of Trypano- 

 soma rhodesiense, it has been isolated 

 from them only once. Heisch, McMahon 

 and Manson-Bahr (1958) isolated it from 

 a bushbuck ( Tragelaphus scriptus) in 

 Kenya by inoculation of a human volunteer. 



Epidemiologic evidence for a wild 

 animal reservoir is exemplified by the ob- 

 servation that every year fishermen and 

 honey hunters become infected with T. 

 rhodesiense near the Ugalla River in the 

 Western Province of Tanganyika, yet this 

 is an uninhabited region, and no people 

 are there at all during the 6-month rainy 

 season. The Ugalla River is part of the 

 Malagarasi river system of the Western 

 Province. It runs thru a sparsely popu- 

 lated, woodland region inhabited by many 

 wild animals and infested with Glossina 

 morsitans . Jackson (1955) described 25 

 cases of sleeping sickness in fly-boys 

 stationed in remote outposts in this area 

 between 1935 and 1939, and concluded 



that there was strong evidence that game 

 was acting as a reservoir. Over half the 

 cases of T. rhodesiense infection diag- 

 nosed in Africa in 1953, 1954 and 1955 

 were contracted in this region (Ashcroft, 

 1958); 2069 cases were reported in the 

 Western Province in these years (Apted, 

 1955). 



The only way to be positive that a 

 brucei-Hyie strain of trypanosome isolated 

 from wild animals is actually T. rhodesi- 

 ense is to inoculate human volunteers with 

 it, and very few such attempts have been 

 made. In one of the latest of these, Ash- 

 croft (1958) inoculated a strain which he 

 had isolated from a Coke's hartebeest 

 {Alcelaphus cokei) in Tanganyika into 2 

 African volunteers, but no infection re- 

 sulted and he concluded that the organism 

 was T. brucei. 



The life cycles of the human trypano- 

 somes are the same as that of T. brucei. 

 The vectors are species of tsetse flies of 

 the genus Glossina. The chief vectors of 

 T. gambiense are the riverine tsetse flies, 

 G. palpalis and G. tachinoides, while 

 those of T. rhodesiense are the game 

 tsetse flies, G. morsitans, G. swynner- 

 toni and G. pallidipes. 



Human trypanosomosis is similar to 

 nagana in its manifestations. For further 

 information, any human parasitology text 

 may be consulted. 



TRYPANOSOMA EVANSI 

 (STEEL, 1885) BALBIANI, 1888 



Synonyms : T. soudanense, T. 

 elepfiantis, T. annamense, T. cameli, 

 T. marocanum, T. ninae kohl-yakimov, 

 T. aegyptum, T. hippicum, T. venezue- 

 lense. 



Disease : Trypanosomosis due to 

 T. evansi has been given different names 

 in different localities. The most widely 

 used name, surra, is applied to the dis- 

 ease in all hosts. The disease in camels 

 is called el debab in Algeria and mbori in 

 Sudan. That in horses is called murrina 

 in Panama and derrengadera in Venezuela. 



