TRYPANOSOMES OF HORSES 45 



their hosts. They rest awhile, during which period 

 some of the trypanosomes escape digestion ; but 

 when hunger forces the flies to feed again, the big 

 game may be miles away. Nearer at hand, perhaps, 

 are newly imported cattle, forming a suitable food- 

 supply. A few plunges of the flies' proboscides and 

 the inoculation of the trypanosomes into the new 

 host is complete. The parasites develop rapidly 

 and the cattle succumb. 



In South India railway development has been re- 

 tarded to a great extent by the difficulty of transport 

 of materials. Horses and other baggage animals 

 are victims of a trypanosomiasis for which the 

 native name is " surra." Certain Tabanid flies are 

 concerned in spreading this parasite. Another note- 

 worthy fact that has an important bearing is that 

 surra has spread from India to Mauritius, with most 

 serious results to the cattle and horses in the island. 

 There is strong probability that the infected flies 

 were imported with fodder used for the horses, and 

 also that a few infected horses were introduced 

 unawares. As the hosts in Mauritius were new to 

 the trypanosomes (T. evansi) inoculated into them by 

 the flies, they rapidly fell victims to the malady. 



In South America trypanosomes are responsible 

 for much loss among the horses employed on the 

 cattle ranches. The disease, known as " mal de 

 caderas," runs a rapid course and is usually fatal. 

 The cause of the malady is Trypanosoma equinum. 



Trypanosomes that have only been relatively 

 recently introduced into their respective hosts 

 usually are fatal to them. On the other hand, some 



