80 YETEEINAEY HYGIENE 



conditions, though in the laboratory their life may be 

 found to be prolonged from one to three months. 



For these reasons there has been at times great difficulty 

 in accepting the water-borne origin of disease, but no such 

 difficulties apply to the lower animals. Glanders, foot and 

 mouth, swine fever and similar diseases are not transmitted 

 along the water-mains of any company. 



The water-trough or bucket in the stable, the puddle or 

 polluted well in the farmyard are the means of infection ; 

 the water and the disease are side by side, not as in the 

 human subject probably some miles apart. 



Anthrax infection through contaminated water is possible, 

 and many such cases have been reported, but the bulk of 

 evidence points to the food as the chief means by which 

 the microbe enters the body. 



Parasitic diseases so common in the lower animals are 

 largely spread by water ; the ova of tape, round, and thread 

 worms have been found in water ; certain filaria such as 

 the filaria oculi are undoubtedly conveyed by it, while the 

 liver fluke of the sheep can only be transmitted by passing 

 through an intermediate host that lives in the water or in 

 wet places. 



The attack of leeches both in the nasal passages and on 

 the limbs of horses can only occur through water. In fact, 

 it is possible that by far the most common source of para- 

 sitic infection of animals is through the water supply. 



We have been compelled within the last few years to 

 modify views which were previously accepted facts in 

 connection with water and disease. It is by no means 

 clear that any particular inorganic impurity in water 

 accounts for goitre; it is now almost certain that while 

 cystic calculus frequently occurs on a limestone formation, 

 lime or hardness of the water has practically nothing to 

 say to its production. Finally, abortion amongst animals, 

 which has in some years from its frequency been described 

 as epizootic, and considered to be due to the impregnation 

 of water by sewage, is now known to be caused by a specific 

 organism which enters from without. 



Digitized by Microsoft® 



