584 The Blood Flagellates 



Sudan. Within these areas, high temperatures (75-85° F.) favor develop- 

 ment of the trypanosomes in tsetse flies, while temperatures below 70° 

 are unfavorable. A few outbreaks of epidemic proportions have been 

 recorded, but the disease is generally sporadic in occurrence. 



Fig. 12 2. Trypanosoma gamhiense. A-D. Stages in Glossina palpalis 

 (x3300, after Robertson): A. Stage in mid-gut after two days; B. Stage in 

 gut after 2-3 weeks; C. Crithidial stage in salivary glands; D. Metacyclic 

 trypanosome in salivary glands. E-I. Stages in blood of man; x2200 ap- 

 prox.: E. Slender form (after Laveran); F. Slender form (after Bruce); 

 G. Intermediate form (after Bruce); H. Broad form (after Laveran); I. 

 Broad form (after Bruce). 



The causative organisms. Trypanosoma gamhiense Dutton, first seen 

 by Forde in 1901, is the causative organism of Gambian sleeping sickness; 

 T. rhodesiense Stephens and Fantham, of the Rhodesian type. Although 

 the two parasites differ in virulence, and to a considerable extent in 

 geographical distribution, they cannot be distinguished with certainty 

 from each other or from T. brucei. Some workers believe that T. rho- 



