PROPHYLAXIS 



1209 



It is always easy to find some local fish which will eat larvae readily. Thus, 

 in Bengal the larvae-eating fish are: Haplochilus panchax, H. melasiigma, 

 Ambassis nama, A. ranga, Anabas scandens, Barbus ticto, and several species 

 of Trichogaster. Tadpoles and water-boatmen also eat mosquito larvae. 



7. Growth of weed in water, especially L^wwa, the duckweed. 



8. Attention to the non-stagnation of water in gutters. 



Summary.— Every district must be considered separately, and a 

 systematic malarial survey having been made, those methods should 

 be applied which seem most adapted for success. A combination 

 of methods must be better than any one individual method. In 

 any case, a definite scheme should be devised, and thoroughly 

 and continuously carried out. But a word of caution is necessary. 

 Having made the survey and estimated the cost, firstly, leave a 

 good margin for contingencies, and, secondly, insist upon an 

 adequate supply of money being provided; but it is not necessary 

 to embark upon an expensive scheme, as a great improvement can 

 be effected with but little expenditure. It is, however, important 

 to make a beginning, and to attempt to gain the confidence of the 

 public, as to-day there is no difficulty with the authorities, who 

 are usually very willing to help. 



The methods mentioned above may be summarized as follows: — 



Reduction of Bites. — ^Mosquite-net, screening the house, use of 

 fans, use of hand-net, use of protective oils. 



Mosquito Reduction. — Insects may be killed by hand-net, by culi- 

 cides, by natural enemies, or inconvenienced by diminution of dense 

 vegetation. 



Larvae may be attacked by removing, oiling, or screening col- 

 lections of water, natural or in plants, by introducing fish or beetles 

 into water, or by the engineering works mentioned above. 



The smaller methods are usually carried out by gangs of workmen 

 — ^mosquito brigades — under trained supervisors. 



Case Reduction. — ^By quinine prophylaxis and by segregation. 



Relative Values. — ^The relative merits of protection against mos- 

 quitoes and quinine prophylaxis have been investigated by Celli, 

 whose results are embodied in the following table: — 



Relative Values of Quinine Prophylaxis and Antimosquito 



Protection. 



Method of Prophylaxes. 



None. 



Quinine 

 Prophylaxis 

 alone. 



Anti- 

 mosquito 

 Protection 

 alone. 



Quinine Pro- 

 phylaxis plus 

 A ntimosquito 

 Protection. 



Percentage of infections . . 



33% 



20% 



2-5% 



1-75% 



Results. — In British Guiana the cases treated in hospitals*have 

 been reduced from 33,748 in 1906-07 to 7,384 in 1912-13. In the 



