238 IOWA DEPARTMENT OF AGRICULTURE. 



The object of hygiene is to secure the greatest degrees of bodily health 

 and vigor, because the animal will develop better and is less liable to 

 contract disease. The water trough, the puddle, shallow and polluted 

 well in the feed lot are the chief sources of infection, although disease 

 germs may be carried along the course of streams from infected farms. 



The parasitic diseases so common in the domesticated animals and 

 which cause such losses in young animals are largely spread by water. 

 The ingestion of impure water contaminated by sewage has been con- 

 demned as a prolific cause of abortion-, but it is now known that unless it 

 carries the specific organism which enters from without, it cannot be 

 considered as a cause of this disease. 



The results of recent experiments prove that contagious abortion in 

 cows is more readily transmitted through the contamination of food by 

 uterine exudate than any other means. Cows fed on contaminated fetal 

 cotyledons or uterine exudate will abort. The disease may be transmitted 

 to sows and for this reason, if for none other, hogs should not be fed on 

 the afterbirth or dead fetus of a cow that has aborted from any cause. 

 A circumstance not to be forgotten is that a cow that has calved a full 

 term may nevertheless sometimes furnish a vaginal discharge that is in- 

 fective and therefore dangerous. 



Parasitic Diseases. — Two divisions are made of parasitic diseases, ani- 

 mals and vegetable. All vegetable parasites are fungi, and the animal 

 belongs to the invertebrates. Parasites are further divided according as 

 they live upon or within the body of the host. 



The part played by these organisms was for a long time not under- 

 stood, some of them, because of their small size, as the trichina spiralis 

 and mange mite escaped detection. 



The gravity of the attack from any one of the species of parasites de- 

 pends on the relative amount of injury caused by the individual parasite, 

 and the number of which the host may be assailed. Thus the necessity 

 of keeping the hog sheds clean to minimize the chances of infesting the 

 occupants. 



The cystic disease of the pig is caused by consuming human excreta 

 or food contaminated by" the same. Thus the better observance of sani- 

 tary precautions in the human population. The thorough cooking of sus- 

 pected beef and pork will remedy this condition as far as man is con- 

 cerned. 



Some parasites like the trichina spiralis and the echino-coccus cysts 

 are so likely to undergo a constant increase in the same locality in future 

 years, that their presence can only be looked upon as a growing menace, 

 and should be exterminated at any cost. If a parasite must pass through 

 a host in order to arrive at maturity, it will be necessary to determine 

 what this host is, and institute measures to prevent the animal coming in 

 contact with, either the host or infecting material which may be thrown off. 



Most parasitisms can be dealt with by changing the condition of the en- 

 vironment, thus cutting off the next generation of the parasitic organism, 

 this injunction is very generally ignored, and will not in the end ex- 

 terminate the infectious principle, the thing so much desired in the ex- 

 termination of the infesting agent. In general we may say that each 

 kind of domestic animal has its parasites, and these may be found only 



