540 TROPICAL HYGIENE, SANITATION, ETC. 



Malarial Diseases. 



Given the parasite and the mosquito, malaria tends to increase with 

 the temperature. Atmospheric humidity favours it by encouraging 

 mosquito breeding and by predisposing to chills in European residents. 

 Clay soil is bad on account of the high subsoil water which encourages 

 mosquito breeding. Complete temporary flooding or good draining 

 will reduce its incidence anywhere. Its prevalence decreases with 

 altitude, other things being equal. 



Relapsing Fever. 



Neither soil nor climate affect this disease. 



Destitution, tilth and overcrowding are powerful predisposing 

 causes. These conditions favour the presence of the soft ticks, e.g., 

 Ornithodorus moubata and Argas persicus, which are blamed as 

 carriers of the disease. 



Leprosy. 



Climate and tropical conditions exercise but little influence upon 

 this disease. Sanitary improvements in habits and surroundings will 

 certainly assist in suppressing it. It has been called a disease of 

 semi-civilization. 



Undulant Fever. 



This disease is carried largely by the infected milk of infected 

 goats. It is also carried by water. 



Pellagra. 



The eruption recurs each spring and autumn. Exposure to the 

 sunlight is a strong predisposing factor of the eruption. 



The symptoms abate during the summer and almost disappear in 

 winter. Agricultural classes are most aft'ected. 



It is almost world-wide in its distribution. 



Trypanosomiasis. 



Insanitary conditions favour the breeding of the Glossin^e which 

 are necessary for its propagation. Destitution predisposes to the 

 disease and raises the case incidence and mortality. 



Dysentery. 

 Personal cleanliness is absolutely essential on the part of the 

 patients and carriers. Excreta are the chief factors of its spread. 

 Poverty, overcrowding and debility give good ground for bacterial 



dysentery. 



Beriberi. 



This is a deficiency disease in all probability. The best food under 

 the best hygienic conditions will prevent its onset and spread. 



