KALA-AZAR 17 1 



time the members of his household were attacked and 

 the disease gradually spread from house to house. Rogers 

 reports that he has observed a similar house or family 

 incidence among his hospital cases of kala-azar at 

 Calcutta. 



All these facts, as well as the success which has attended 

 attempts to stamp out epidemics of kala-azar in Assam 

 by the isolation of patients, coupled with the burning of 

 infected huts, is in favour of the view that the disease 

 is transmitted by some house-infesting parasite, such as 

 a bug. 



A suggestion, based upon the consideration of the low 

 temperature at which the flagellate forms" are developed 

 in vitro from the oval forms obtained from the spleen, is 

 that the parasites escape in the faeces and undergo a stage 

 of development in some cold-blooded animal, a fish or 

 mollusc, and that they obtain entrance into the human 

 body by the ingestion of such alternative hosts, either 

 direct or through the water supply. There is, however, 

 no experimental evidence in support of this suggestion, 

 and the circumstances that the parasites cannot be found 

 in the faeces, and that a sterile medium is required for 

 the development of flagellate forms, are opposed to it. 



The seasonal prevalence of kala-azar, as shown by the 

 number of fresh attacks, is greatest in the cold weather 

 months, November to April, in Assam and Lower Bengal. 

 The " cold weather " temperature in this area ranges 

 between 60 and 75 F., and Rogers points out that it is 

 only within these limits that developmental forms of the 

 parasite are obtainable in vitro. He suggests that 

 epidemics of kala-azar have been due to a succession of 

 periods of prolonged cold weathers, which have extended 

 the conditions favourable to the extra-corporeal develop- 

 ment of the parasite. He further suggests that the more 

 severe cold weather of North-west India accounts for 

 the absence of kala-azar there. 



As has been seen, kala-azar when epidemic may carry 

 off entire households, persons of either sex and all ages 



