TRANSMISSION OF INFANTILE KALA-AZAR 83 



terial which is necessary to produce infection. Injection of 

 infected material under the skin does not transmit the disease, 

 although in nature this is probably the mode of transmission. 

 Evidently, then, the natural means of transmission must be by 

 more powerful or virulent parasites than can be obtained from 

 already infected animals. The common opinion is that the dog 

 flea, Ctenocephalus cams (see p. 416), is the usual transmitting 

 agent, and that this insect serves as an intermediate host for the 

 parasites. This opinion is based on the fact that parasites ap- 

 parently identical with those in infected children have been 

 found in the tissues and faeces of fleas. Brumpt, however, be- 

 lieves that there has been confusion with an apparently harmless 

 flagellate which is frequent in fleas even where infantile kala-azar 

 does not occur. Patton suggests that the kala-azar of dogs may 

 really be an infection quite distinct from the infantile disease and 

 caused by infection with the common intestinal flagellate of fleas, 

 Herpetomonas denocephali. The possibility that the human dis- 

 ease may also be caused by this flagellate seems to have been 

 overlooked; the fact that the fleas do not readily become in- 

 fected from sucking an infected child does not necessarily argue 

 against the origin of the human parasites from fleas. Recent 

 work by da Silva and Spagnolio in attempting to infect fleas by 

 allowing them to feed on a naturally infected child has been un- 

 successful. They fed 25 fleas on an advanced case of the disease 

 and secured no infection of the fleas in 484 feeds. These authors 

 do not believe in the relation of fleas to infantile kala-azar, and 

 point out that the disease is at its height in the spring before 

 fleas have become very abundant. 



Infection of bedbugs with Leishmania infantum is not suc- 

 cessful. If fleas do serve as the usual transmitting agents, it is 

 probable that after development in the flea the Leishman bodies, 

 as suggested above, become more resistant and are able to establish 

 themselves in situations where they would otherwise be destroyed 

 before they had a chance to multiply and adapt themselves. 



Since so many dogs around the Mediterranean are infected, 

 although only a small number give any indication of it, they 

 probably serve as a reservoir for the disease. Not infrequently 

 children attacked by kala-azar have been known to have played 

 with diseased dogs, and it is easy to see how the fleas which 

 almost always infest dogs in these regions could infect children. 



