PROTOZOA 



403 



ervoir" of this parasite. They report the disease in dogs that 

 have devoured the infected capybara. The direct carriers of 

 the parasite from the capybara to horses are not definitely 

 determined. The disease caused by this parasite is charac- 

 terized by rapid wasting (although the appetite is good), rise 

 of temperature and weakness in the hind quarters. Later the 

 animal can not stand. There may be swellings especially over 

 the joints but not pronounced and persistent edematous areas 

 as in nagana. The skin, especially about the neck, shoulders 

 and hind quarters, may be the site of slight eruptions 3 to 4 

 centimeters in diameter from which the hair has fallen and 

 over which scabs form. 



Morphology. According to Laveran and Mesnil, Tr. equi- 

 num is 22 to 24 /* long, by about 1.5 /x 

 wide; but parasites undergoing divi- 

 sion may be 28 to 30 /A long, by 3 to 4 /x 

 wide. In the ordinary forms the 

 flagellum measures about 5 /x. The 

 parasite has the same length in differ- 

 ent species of animals. The measure- 

 ments given that were made of the 

 parasites taken from the mouse, rat, 

 monkey, guinea pig, dog, and horse 

 are identical. 



In fresh blood Tr. equinum very 

 closely resembles Tr. Evansi and Tr. 

 Brucei; it is only in preparations 

 which are well fixed and stained that 

 one is able to distinguish between 

 them. Tr. equinum is very active 

 when the blood is drawn, but in ordi- 

 nary fresh preparations it loses its 

 motility fairly quickly. In animals 

 with many trypanosomes in their 

 blood the movements of the parasites 

 usually become sluggish during the 



few hours immediately preceding death, probably owing to 

 the asphyxial condition present. 



Fig. 90. Trypanosoma 

 equinum from blood of 

 a mouse. (After Nocht 

 and Mayer). 



