How Insects Cause or Carry Disease 45 



often an important pest of horses and cattle. Its 

 blood-sucking habit makes it quite possible that 

 it too may be concerned in carrying anthrax and 

 other diseases. 



In a later chapter it will be shown how the tse- 

 tse-fly, which is somewhat like the stable-fly, is 

 responsible for the spread of the disease known 

 as the sleeping sickness. This disease is caused 

 by a Protozoan parasite, a trypanosome, which is 

 transmitted from one host to another by the tse- 

 tse-fly. 



In Southern Asia and in parts of Africa there is a 

 very serious disease of horses known as surra which 

 is caused by a similar parasite (Trypanosoma 

 evansi). This parasite attacks horses, mules, 

 camels, elephants, buffaloes and dogs, and has been 

 recently imported into the Philippines. It is sup- 

 posed that flies belonging to the same genus as the 

 horse-fly (Tabanus and others), and the stable-fly 

 (Stomoxys) and the horn-fly (Hcematobia) are re- 

 sponsible for the spread of the disease. 



Nagana is one of the most serious diseases of 

 domestic animals in Central and Southern Africa. 

 In some sections it is almost impossible to keep any 

 kind of imported animals on account of this disease 

 which is caused by a parasite (Trypanosoma 

 brucei) similar to the one causing surra. This 



