806 



Nagana. 



up with certainty. Some enzootics have a great similarity to nagana, 

 while others are more closely related to surra (see also p. 837 and 

 p. 812). 



Etiology. The Trypanosoma brucei, recognized as the cause 

 of nagana, is on an average 25-33 i^ long, 1.5-2.5 /* broad, and 

 possesses a central oval nucleus, a blunt, Indian-club-shaped 

 posterior end, slightly developed undulating membrane, and 

 long flagellum (Fig. 141). Under the microscope it exerts a 

 lively snake-like movement, but without pronounced locomotion. 



Pathogenicity. Inoculation of blood containing trypano- 

 somes, under the skin or into the blood circulation of horses, 



causes after from 2 to 6 days a marked 

 elevation of temperature and in the 

 first case also a painful swelling at 

 the point of injection. About the end 

 of the first week the fever diminishes 

 but reappears later at certain inter- 

 vals,_ and during the duration of the 

 febrile attack trypanosomes may be 

 demonstrated in great numbers in the 

 blood. In the meantime edematous 

 swellings appear on the lower abdo- 

 men, and in the vicinity of the ex- 

 ternal genital organs; the animals 

 emaciate in spite of continuous, and 

 often ravenous appetite ; marked mus- 

 cular atrophy and also pronounced 

 anemia develop. Sometimes turbidity and ulceration of the 

 cornea results with subsequent iritis. Finally a condition re- 

 sembling lumbar paralysis sets in, whereupon the animals die 

 from 15 days to 4 months after the appearance of the first 

 symptoms. In donkeys and mules the clinical picture is similar, 

 although sometimes with a still more protracted course after 

 artificial infection; the zebra is also susceptible to artificial 

 inoculations ( Martini ) . 



In cattle, also in sheep and goats the inoculation usually 

 results in a chronic disease. 



Dogs and eats are very susceptible to infection, and likewise become 

 affected under symptoms of recurrent fever, edamatous swelling of head, 

 chest, gradual emaciation and loss of strength. Guinea pigs, rabbits, rats 

 and mice, are very easily infected artificially, while hogs show consider- 

 able resistance to artificial inoculation. Monkeys are very susceptible and 

 usually die a few weeks after the infection. Of fowls only geese (Schil- 

 ling) and chickens (Goebel) could be infected artificially, while other 

 birds showed no symptoms of disease. 



Horses and other solipeds, then cattle, more rarely sheep 

 and other ruminants, become most frequently affected as a 

 result of natural infections. 



Fig. 141. Trypanosoma Bru- 

 cei. Guinea pig blood. Stain- 

 ed after Komanowsky-Ziemann. 



