IC|6 PROBLEMS AND PRINCIPLES OF MALARIA PREVENTION. 



great believers in the possibilities of this method, and it was 

 tried out on a huge scale in Daressalam, in German East Africa, 

 between the years 1904-13. The results were far from encourag- 

 ing, even in that comparatively small community. 



(2) The Reduction to a Non-infective Minimum of tlie 

 Number of AnopJielincc of the Sf^ecies capable of Transmitting 

 Malaria. — This is the plan which has been pursued, with what 

 success most of us know, in Khartoum, Ismailia, and Panama, 

 and is the plan now generally acknowledged to 1)e the most pro- 

 mising of results. I shall therefore go into a little detail as 

 to the technique involved. 



In order to insure to a reasonable degree the >uccess of 

 this plan, it is necessary to make a careful preliminary study. 

 The points to be determined are : — 



(0) The incidence rate of malaria in the locality. 



{b) The species of Anophelinse prevalent in the locality. 



(c) Which of these species are capable of transmitting malaria. 



(d) What are the life cycle and breeding habits of these species. 



(c) What are the probable flight ranges of these species under the 

 existing climatic conditions. 



In connection with the last, and to show the importance of 

 such a stud}'. I might mention that we were ver}- much sur- 

 prised in Panama to discover that the malaria-transmitting 

 Anophcle-> prevalent there travelled more readily against the wind, 

 piovidcd its velocity did not exceed about five miles per hour, 

 than with the wind, as is generally assumed to be the case. The 

 discovery resulted in the saving of considerable amount of money 

 in the drainage and treatment of certain areas. We actually 

 were able to leave untreated considerable areas to the windward 

 of certain villages without in any way influencing the malaria 

 rates of these villages. 



Having obtained the data outlined above, it should be 

 possible for a competent man to prepare a map on which mos- 

 fiuito-breeding areas of the territory in which the dangerous 

 species of Anophelinse breed would be shown, and to prepare a 

 scheme for effectively treating these areas, together with a 

 reasonably correct estimate of the costs involved. 



Anopheles-hvetdxng areas vary from flowing streams to 

 marshes the consistency of porridge. Some species breed in 

 fresh water only, and the larvae die out with an apparently insig- 

 nificant admixture of sewage or salt water. Other species will 

 breed in water considerably contaminated with sewage, and in 

 almost pure sea water. Some species breed in small collections 

 of water such as one finds in roof gutters, hollow trees, at the 

 junction of the leaves with stems of such plants as the banana, 

 etc. Each one of these breeding places must be treated in the 

 manner appropriate to the case and consistent with the economical 

 claims of the community, such as the reasonable claims of the 

 agriculturists, the household owners, the gardeners, the power 

 plant owners, potable water reservoirs, the cattle owners, who 

 may object to their watering places being contaminated with 



