MASTIGOPHORA 



753 



FIG. 175. TSETSE FLY (Glossina palpalis). (From 

 Rosenaii) "Preventive Medicine and Hygiene.") 



flies, however, the trypanosomes multiply in the intestinal tract, and 

 after eighteen to fifty -three days they again become infectious and re-; 

 main so for a long 

 period, the parasites be- 

 ing found regularly in 

 the salivary glands and 

 in the proboscis. 



It is possible that the 

 disease is transmitted in, 

 other ways than by 

 Glossina palpalis ; blood- 

 sucking insects, such 

 .as stomoxys, anopheles, 

 mansonia and perhaps 

 fleas, may act as me- 

 chanical carriers. It is 

 also possible that the 

 'disease is transmitted 

 ,by coitus. Without some 



:such explanation it is difficult to understand certain house epidemics 

 which have occurred outside the fly belts. 



The animal host of the Trypanosoma gambiense is believed to be 

 the big game animals, particularly the antelope. 



Morphology. The organism belongs to the brucei group, and its 

 'differentiation on morphology is difficult, yet, on the average, the 

 posterior end is somewhat more pointed than the brucei. In length 

 it varies from fifteen to thirty microns, and in thickness from one to 

 three microns. In fresh preparations the motility is not. marked; 

 both plump and slender forms are found in the blood, but in the cere- 

 bro-spinal fluid slender forms only are seen. 



Cultures on blood agar have been made by Thompson and Sinton, 

 yet they died out after a few weeks, and were never virulent. The 

 pathogenicity varies somewhat with the strain used, but apes are easily 

 infected. In white rats there may be two or three relapses before 

 death occurs, while when inoculated with brucei death follows within 

 two weeks. 



Pathogenicity. Although cultures vary greatly in virulence, it is 

 possible to infect rats, dogs and monkeys with a fatal trypanosomiasis ; 

 cattle, sheep and goats continue to show a few parasites for months 

 after inoculation but without sickening. In no animal, however, is 



