HUMAN DISEASES 55 1 



may produce cirrhosis of the hver, a certain degree of which is 

 common amongst natives in East and Central Africa. With these 

 and a few other exceptions, the resuks of mass infestation by hel- 

 minths are little known, but there can be no doubt that the general 

 physical and mental activity of heavily infected persons must be 

 impaired. 



The relation of helminthiasis to nutrition is a question calling 

 for examination. It is clear from experience in many parts of the 

 world that certain parasitic worms flourish chiefly in subjects who 

 are weakened in other ways, perhaps by insufficient or unbalanced 

 diet {see pages 563 and 576). But in the African population heavy 

 infestation may be a cause of malnutrition rather than an effect. 

 There are several important worm infestations which are definitely 

 known to be uninfluenced by the malnutrition of their hosts. In 

 certain cases feeding habits may have direct effect in causing 

 infection, particularly in the case of peoples who eat raw meat and 

 those who enrich their supply of mineral salts by eating earths, etc., 

 from special areas [see page 578). 



To indicate the severity of infection in different territories the 

 following notes have been taken from recent medical reports. In 

 Southern Rhodesia schistosomiasis is the most important helminth 

 disease, with hookworm taking a second place. Schistosomiasis 

 surveys have been carried out in this territory as well as in the 

 Union of South Africa and indicate that the incidence varies 

 widely in different districts. Among the native population it 

 reaches 50 per cent in certain areas and even for European chil- 

 dren, figures as high as 36 per cent have been recorded in Southern 

 Rhodesia. In the Union propaganda led to the sanitary protection 

 of bathing places, and treatment campaigns have been organized 

 by the Transvaal Bilharzia committee in co-operation with school 

 medical officers. In Northern Rhodesia it has been found that 

 3 1 per cent of workmen recruited by the Rhokana Corporation 

 are infected with hookworm. Helminth diseases are common in 

 Nyasaland, 140 out of 1,494 cases at the Zomba Native Hospital 

 were admitted on account of hookworm, and 47-2 per cent of all 

 other cases were infected with these helminths. In one village in 

 Kuweraza district 100 per cent of the people examined gave posi- 

 tive reactions. That drainage may play an important part in 



