PART X — ENVIRONMENTAL CONTAMINANTS 



5. ENVIRONMENTAL DISEASE 



Malaria 



Malaria in humans continues to be 

 a major problem in many parts of 

 the world. Uncritical enthusiasm gen- 

 erated in the period immediately after 

 World War II, occasioned by the un- 

 expected appearance on the scene of 

 the chlorinated hydrocarbons, led to 

 the belief that global eradication of 

 malaria was a possibility. National 

 and international agencies invested 

 large sums of money in sweeping pro- 

 grams, built upon the observations 

 that the residual effects of long- 

 persisting insecticides, when these 

 had been applied to the walls of 

 dwellings, would serve to interrupt 

 the transmission of malaria by cut- 

 ting short the lives of the vector 

 anophelines, thus denying to the para- 

 site the chance to infect new hosts. 



There were early victories in re- 

 gions where the habits of the specific 

 vector species led, in a certain few 

 instances, to actual eradication of the 

 vector or, in other instances, to inter- 

 ruption of transmission and eradica- 

 tion of malaria. In still other instances 

 victory was partial, and marked re- 

 duction in incidence of malaria could 

 he noted. (See Figure X-18) In other 

 instances, notably in Africa, parts of 

 Asia, and parts of South America, 

 results have been disappointing. 



In the large-scale campaigns, em- 

 phasis was placed almost entirely on 

 control procedures and the intricate 

 logistic problems relating thereto. For 

 a period of two decades, there was a 

 decided slump in the volume of basic 

 malaria work carried on; fundamental 

 studies on parasite biology, host- 

 parasite interactions, drug prophylaxis 

 and therapeusis, and the biology of the 

 anopheline vectors were neglected. 



The recognition that resistance to 

 insecticides was emerging in anophe- 

 line vectors (not as serious a problem 



Figure X-18 — CHANGES IN MALARIA MORBIDITY 

 BEFORE AND AFTER MOSQUITO CONTROL 



Area 



Year 



Number of Cases 



Mauritius 



Cuba 



Dominica 



1948 

 1969 



1962 

 1969 



1950 

 1969 



46,395 

 17* 



3,519 

 3 



1,825 

 Nil 



The table shows the effectiveness of selected mosquito-control programs, most of 

 which use DDT. Over 1,000 million people have been freed from the risk of malaria 

 through such programs. 



364 



