PATHOGENIC PROTOZOA OF THE MASTIGOPHORA 429 



The subcutaneous tissues are infiltrated and edematous. It is 

 practically invariably fatal. Cattle are relatively resistant to the 

 disease, and in these animals recovery usually occurs, but the blood 

 may remain infective for a considerable period. Buffalo frequently 

 succumb. Camels, elephants, and dogs are not infrequently 

 infected. 



This disease resembles nagana clinically, and the causal organ- 

 isms can scarcely be differentiated. Animals immunized against 

 the one disease are susceptible to the other, which would seem to 

 establish specific differences sufficient to separate the organisms 

 as distinct species. 



Bacteriological Diagnosis. The organisms gradually increase in 

 numbers in the blood during the onset of the disease, and have been 

 found as numerous as 350,000 per cubic millimeter. They are 

 frequently not present in the blood between the periods of fever. 



Transmission. Fraser and Symons state that in the Federated 

 Malay States four species of the fly genus Tabanus, particularly 

 T. fumifer, are responsible for the spread of the disease. Probably 

 other flies may carry the organism as well. Experiments seem to 

 show that the transference in this case is merely mechanical, and 

 that there is no developmental cycle in the intermediate host. 

 Carnivorous animals may be infected by ingestion if there are 

 lesions in the mucous membranes. 



Trypanosoma brucei 



Disease Produced. Nagana or tsetse-fly disease in horses, 

 cattle, camels, buffalo, antelopes, and related wild animals, pos- 

 sibly the elephant. 



The fact that this disease follows the bite of the tsetse fly has 

 long been known by African natives, and the early explorers con- 

 firmed their belief. Bruce, in 1896, described the trypanosome 

 which causes the disease. 



Distribution. Known only in Africa, particularly in Zulu land. 



Morphology. The organism is sluggishly motile. It is usually 

 between 25 and 30 u in length and 1.5 to 2.5 (i in width. Granules 

 may generally be observed in the protoplasm. Irregular forms 

 occur in the blood after death, and in the lymphatic glands, spleen, 

 bone-marrow, liver, and lungs during life. Kleine believes, from 



