HUMAN DISEASES 553 



is by no means satisfactory on account of irregular symptoms, so the 

 incidence is almost certainly higher than is popularly supposed. 

 Inoculation against these diseases has reduced much of the risk to 

 Europeans living in unhealthy areas; for example, the adoption 

 of general inoculation of Europeans in the Belgian Congo has 

 reduced the cases from 38 in 1928 to only 3 in 1934. Experience 

 in temperate countries indicates that it is unlikely that the typical 

 group of diseases will disappear from the tropics until the standard 

 of sanitation has been raised to that which now exists in the large 

 towns in civilized Europe. 



TAWS AND VENEREAL DISEASES 



The difficulty of distinguishing between infections from yaws 

 and syphilis in native patients causes trouble in estimating the 

 prevalence of these diseases, but throughout Africa there is no 

 doubt that the spirochaetal diseases must be regarded as of far 

 greater importance than the more obvious diseases already dis- 

 cussed, with the exception perhaps of malaria and sleeping sick- 

 ness. Practically all estimates ofincidence are based on attendances 

 at hospitals and clinics, and therefore give a poor idea of these 

 diseases in rural areas. A few general estimates, however, have 

 been put forward; thus in East Africa the incidence of yaws and 

 syphilis together was put, until quite recently, at some 60 per cent 

 of the population, but the treatment campaign of recent years 

 has probably reduced this considerably. In Tanganyika the pro- 

 portion of yaws and syphilis together to other parasitic diseases 

 was 57 per cent in 1929, but had dropped to 37 per cent in 1933. 

 In 1 936, the cases treated at Government institutions were syphilis, 

 23,484; yaws, 70,682, and gonorrhoea, 9,619. Compared with 

 these, in Uganda the figures were syphilis, 63,695; yaws, 62,240; 

 gonorrhoea, 14,101. The history of venereal diseases in East 

 Africa is somewhat obscure, but it is fairly clear that syphilis has 

 been established there much the longest, since it probably arrived 

 with the Arabs and was prevalent long before the European occu- 

 pation. 



In West Africa, where in general gonorrhoea is the more impor- 

 tant in southern territories and syphilis and yaws in the northern 

 areas, rough estimates of incidence range from 50 per cent to 90 



