426 NAGANA 



NAGANA 



Synonym. Tsetse-fly disease. 



§ 333- Characterization. Nagaua is a disease charac- 

 terized by anemia and rapid emaciatiou caused by one of the 

 trypanosoma. It attacks horses, mules, zebras, cattle, and 

 sheep. A number of the smaller animals are susceptible. It 

 is known to all dialects as the tsetse-fly disease. 



§ 334. Geographical distribution. This disease is 

 found in central and southern parts of Africa. There seems 

 to be some doubt about its identity with the disease of a simi- 

 lar nature in the Transvaal. 



§ 335- History. Livingston pointed out the existence 

 of this disease in Central Africa. In 1886, Bruce studied it in 

 the Zulu Land. He found constantly in the blood of the sick 

 animals a trypanosoma similar to that found in surra. It has 

 been carefully studied by Kanthack, Durham and Blandford, 

 Koel, Plimmer and Bradford, Theiler, Schilling, Laveran and 

 Mesnil. 



§ 336. Etiology. This affection is caused by Trypa- 

 nosoma Brucei. It is from 28 to 33 yw in length with the flagel- 

 lum and about i /< in width. It is closely related to Tr. 

 equiperdum. Some investigators have been unable to satisfac- 

 torily differentiate the two species, while others recognize them 

 as distinct. 



The trypanosoma are transmitted from the diseased to the 

 healthy animals by means of the tsetse-fly {Glossina morsiians), 

 which exists in certain parts of Africa. It appears that this is 

 the only species of insect responsible for the transmission of 

 the virus. The affection is extended into uninfected areas by 

 the introduction of diseased animals. 



The period of incubation, vaaxW^cxaWy '^xodiMC^A cases, is 

 reported to be about 4 days in the horse. 



§ 337- Symptoms. The first indication of the disease 

 is a rise in temperature which lasts for 3 or 4 days, when it 



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