PATHOGENIC PROTOZOA OF THE MASTIGOPHOKA 431 



Centrifugation of the blood will frequently result in the collec- 

 tion 'of the organisms in a layer just at the surface of the cor- 

 puscles. 



Transmission. The disease is commonly transmitted from one 

 animal to another by the bite of the tsetse fly (Glossinia mwsitanx). 

 The herbivorous animals native to sections of the country where the 

 disease is prevalent are almost invariably infected, and render 

 infection of other animals easy. Kleine experimentally showed 

 that another species of Glossinia (G. palpalis) could transmit the 

 disease. He found that the flies did not become infective until 

 eighteen days had elapsed. Other experimenters have found that 

 the fly lost its infectiveness within a day or two after feeding upon 

 an infected animal, and have concluded that transmission is wholly 

 a mechanical affair. It seems possible that transmission may 

 occur mechanically in this manner, or there may be a true develop- 

 mental cycle in the body of the insect. 



Trypanosoma equinum 



Synonym. Tr. elmassiani. 



Disease Produced. Mai de caderas of the horse (Spanish 

 caderas = rump or hindquarter) . 



Elmassian, in 1901, announced his discovery of the specific 

 trypanosome of this disease in Paraguay. Voges, in Argentina, 

 confirmed this discovery in the following year. The disease is 

 so prevalent in some sections that cattle are used exclusively for 

 riding and driving. 



Distribution. Parts of South America, particularly Brazil, 

 Paraguay, and Argentina. 



Morphology. This trypanosome resembles those of surra and 

 nagana, but the blepharoplast is so inconspicuous that it may be 

 readily overlooked. The cell is usually between 22 and 24 a in 

 length and 1.5 u. in width. Cells about to divide are somewhat 

 larger. The difference in the blepharoplasts of this and most other 

 forms renders identification easy even in mixed infections. 



Pathogenesis. Experimental Evidence. Inoculation of the 

 organism causes a fatal infection in the horse; the mule and donkey 

 are somewhat more resistant, as are mice, rats, and other rodents, 

 rabbits, and other laboratory animals. Birds cannot be infected. 



