1904.] L. Rogers — Special Report on Fever in Dinajpur Dist 61 



Malarial Commission, although they showed that it can be artificially in- 

 fected. More recently Major Adie^ in the Punjab found one of these 

 anopheles to contain sporozoits resembling those of human malaria, but 

 it is clear that it is not a common carrier of the disease. Unfortu- 

 nately very few A. Listoni could be obtained for dissection, and no sporo- 

 zoits were found in them. This is not surprising, for these dissections 

 were carried out in the cold month of January, and it is well known 

 that a certain temperature is necessary to allow of the development of 

 the malarial parasite in mosquitoes. In a previous paper I showed* 

 that the number of cases of malarial fever fell off very rapidly in a 

 suburb of Calcutta as soon as the minimum temperature fell to 60F., 

 doubtless for the reason just mentioned, and as the minimum tempera- 

 ture in Dinajpur in January was much below that point it is not sur- 

 prising that no sporozoits could be found. 1 had hoped to be able to 

 ascertain if the A. Listoni was infected when the weather had become 

 warmer again, and just before leaving Dinajpur in the middle of March, 

 I tried to collect the necessary mosquitoes, but thiey were still as scanty 

 as earlier in the year, so I was not able to obtain them in sufficient 

 numbers for dissection. This point can only be settled in the rainy 

 season, but as Dinajpur is close to Jalpaiguri, where the Malaria Com- 

 mission found the A. Listoni to be infected later in the year than the time 

 of my inquiry, there can be little doubt that this is the variety which 

 is mainly responsible for the prevalence of malaria in Dinajpur and the 

 neighbouring districts, for I also found this species in small numbers 

 in the northwest corner of the Purnea district. 



The Possibility op Destroying Anopheles in Lower Bengal. 



It will be convenient in this place to discuss the practicability of 

 attempting in Lower Bengal to destroy those anopheles which carry the 

 infection of malaria as a method of malarial prophylaxis. It will be 

 clear from what has been written above that it would be an utter waste 

 of money and labour to attempt to destroy all the different kinds of 

 anopheles, when only one, or possibly two, of them, have been found to 

 carry the disease in nature. Thus, it is now generally admitted from 

 dissections of many hundred A. Rossii that these are never found to be 

 naturally infected, although they can be infected by artificial means, 

 and are thus theoretically capable of conveying the disease. For the 

 same reason, we may exclude from our consideration the swamp species 



1 Adie, Indian Medical Oazette, 1903. 



* The seasonal prevalence of anopheles and malarial fever in Lower Bengal 

 and the practical application of the mosquito theory. Journal of EygienCf October 

 1901, 



