PROPHYLAXIS 185 



somidae (Bilharzia). Bathing, therefore, is a more real 

 danger. Working in soil or mud is believed by some to be 

 a fertile source of infection. Boots for Europeans form 

 a sufficient protection. Natives, who cannot afford these 

 luxuries, can be protected by walking through any of 

 the liquid pitch combinations, such as Barbados tar. 



As regards the larvae, such as those of Filaria bancrofti 

 and F. loa, which are injected by arthropods, protection 

 from the infected insects is necessary. 



In some cases the infection is conveyed by food con- 

 taminated carelessly with infected earth. Uncooked and 

 insufficiently washed vegetables, badly cleaned utensils, 

 and use of the fingers fouled with infected earth may 

 also be sources of infection. The use of uncooked 

 vegetables in any district where human excreta are used 

 for manure should be abandoned, and other vegetables 

 be thoroughly cooked. 



Meats and fish must also be thoroughly cooked to 

 destroy any larval cestodes, trematodes, or trichinae. 

 Imported foods, such as uncooked sausages, salted or 

 partially cured meats, must be similarly treated before 

 use. 



Though much can be done to protect individuals, the 

 protection of a community is a different matter, and 

 should be dealt with by preventing, as far as possible, the 

 dissemination of the eggs and larvae of parasites. It is 

 not only persons who are ill that harbour the parasites, 

 many in good health have a few, and both classes 

 distribute eggs and larvae wherever they defaecate, and 

 the faeces, the eggs and the embryos developed from them 

 are washed into the water, or into the earth at the edge 

 of it, or else they infect mosquitoes and biting flies 

 wherever they go. 



It is difficult to control the developmental stages passed 

 outside the body. The thick-shelled eggs are very 

 resistant. It is impossible to treat earth with antiseptics 

 on a large scale, or to destroy snails, molluscs, or fish 

 wholesale without the balance of life in such places being 



