1292 



THE KALA-AZARS AND PSEUDO-KALA-AZARS 



get into water, from which they can be ingested by some aquatic 

 arthropods, many of which naturally contain flagellates. 



The work of Laveran and Franchini, of Fantham and Porter, has 

 demonstrated that these natural arthropodal parasites can by in- 

 gestion or by inoculation produce a fatal illness resembling kala- 

 azar in mammals. Archibald, experimenting with human kala-azar 

 parasites in the Sudan, has shown that monkeys can be similarly 

 infected by feeding with kala-azar material, and this, together with 

 the curious endemicity of the disease in the Sudan, and with Laveran, 

 Franchini, Fantham, and Porter's researches, make the possibility 

 of water carriage of cysts from infected arthropods to man worthy 

 of consideration. 



From the above it will be clear that, though the parasite is known, 

 the method of infection is still unknown, and the cultivation of the 

 parasite into flagellate form clearly indicates that this is part of the 

 life cycle. 



The predisposing causes appear to depend upon, and be capable 

 of explanation by, the habits of man. Thus the disease, when 

 epidemic, alwa37s spreads relatively slowly along channels of human 

 intercommunication, and apparently is directly due to the intro- 

 duction of an infected human being into the district. It runs in 

 families, in which children particularly suffer, while the class of 

 people who are mainly affected are the poorer sections of the 

 European and native communities. Season and sex appear to 

 have no influence, but there is no doubt about the infection of the 

 dwelling or perhaps its water-supply, nor of the capability of the 

 disease spreading from one dwelling to another, or from one water- 

 supply to another. 



Pathology. — Introduced into the bod}/, the parasite appears to 

 enter the endothelial cells of a capillary bloodvessel or lymphatic, 

 and to grow therein, and to increase in numbers by simple fission 

 until a very large number — Leishman say^ upwards of 220 — ^may 

 be counted in one cell. The organs principally affected in this 

 manner are the liver, spleen, bone-marrow, and lymphatic glands, 

 and, to a less extent, the pancreas, kidneys, suprarenals, testicles, 

 and lungs. 



The parasites may now escape from the enclosing cell by rupture, 

 and are then taken up by the leucocytes, particularly by the poly- 

 morphonuclears, but also by the mononuclears and rarely by the 

 eosinophiles, by means of which they appear in the peripheral 

 blood even in early cases, but are much more common late in the 

 disease, especially if there is diarrhoea due to ulceration of the 

 intestine, in which condition the polymorphonuclear leucocytes 

 are increased in numbers in the peripheral blood, and many of 

 them contain parasites. The further development has still to be 

 worked out, as all that is definitely known is that in cultures the 

 parasite becomes flagellate. 



It would appear as though the parasite could produce some vSort 

 of toxin which causes the marked changes in the spleen^ liver, and 



