430 VETERINARY BACTERIOLOGY 



his experiments with fly transmission, that there must be a develop- 

 mental stage occurring in the insect. 



Isolation and Culture. Novy and MacNeal succeeded in grow- 

 ing the organism of nagana in the medium already described. Only 

 a few tubes out of a large number were found to show growth. 



Pathogenesis. Experimental Evidence. Inoculation of the 

 mouse, rat, dog, cat, and monkey results in an acute infection; of 

 the rabbit, guinea-pig, equines, and swine, in a subacute infection; 

 and of cattle, goats, and sheep, in a chronic infection. 



Character of Disease and Lesions Produced. The disease is of 

 greatest importance in the equines. The incubation period is 

 from three to twelve days (Theiler). -There is a continued or 

 remittent fever and a watery discharge from the eyes and nose. 

 The animal becomes much emaciated before death, which usually 



Fig. 189. Trypanosoma brucei (adapted from Gonder and Sicber). 



occurs in from two weeks to three months. Edema of the ventral 

 region is common. Hypertrophy of the spleen is the most constant 

 lesion. The lymph-glands are generally enlarged. 



Immunity. Rodet and Vallet believe that the organism is 

 rapidly destroyed in the spleen. No practicable method of im- 

 munizing against the organism has been developed. It has been 

 found that the injection of human serum into laboratory 

 animals at intervals will greatly prolong their life, but will not 

 cure. There is probably some relationship between immunity 

 of man and the trypanicidal character of his serum. Goats, 

 sheep, and cattle show a considerable percentage of cures and 

 are thereafter immune. Their serum, however, has little im- 

 munizing power. 



Bacteriological Diagnosis. 'Stained mounts of the blood from 

 infected animals will generally reveal the chani<-teri-iir parasites. 



