MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 825 



Leishmania (Ross, 1903) 



The three parasites belonging to this genus which require mention are included 

 by some authorities in the genus Herpetomonas but the differences with respect to 

 habit of life justify the recognition of a distinct genus. Herpetomonads live in the 

 alimentary tract of various insects, for example, of the common blow fly and are 

 extracellular parasites. Their bodies in genera,l are rigid. Leishmania is, on the 

 other hand, an intracellular parasite and in the flagellated phase of its develop- 

 ment its body is plastic and bends during locomotion. Three species are 

 recognized in association with three distinct types of disease. 



Kala Azar 



Leishmania donovani — Laveran and Mesnil, 1903 



This disease occurs in certaiti parts of Asia being first noted in 

 Assam, Northern India. 



It is caused by L. donovani (Fig. 173). The parasite is rarely found in the blood; 

 when it is seen there, it almost never occurs free but is found in variable numbers 



Fig. 173. — Leishmania donovani. Free organisms and several within cells. {After 



Donovan, from Doflein.) 



within phagocytic cells. It is, usually, easily found by an examination of the 

 juice obtained from the spleen or lymph nodes by puncture with the needle of a 

 syringe. The liver is enlarged and it, also, contains parasites. As the organisms 

 are seen in preparations of spleen juice, they are small ovals measuring about 2m in 

 length and i-Sm ia width. They consist of cytoplasm, in which lie two chromatic 

 bodies one of them large and rounded, the other small and rod-like. This form of 

 the parasite may multiply in the body of the host, by binary or multiple division. 

 If spleen pulp, or blood, containing such organisms be placed on a suitable culture 



