450 HORSE, SWINE AND POULTRY DISEASES 



have previously visited farms where hog cholera exists. It may also 

 be carried in this way by dogs, and by crows and other birds. It has 

 been claimed, and considerable proof has been brought to show it, 

 that the disease may be carried downstream from herds which are 

 affected above. It is therefore well to avoid placing hogs so that 

 they will have access to streams which pass through other farms. As 

 diseased hogs are frequently transported by rail, it is quite possible 

 for infection to be introduced into a farm by litter dropped from 

 cars in transit, especially if hogs on the farm have access to the 

 tracks. 



After hog cholera has visited a farm, the lots, hog houses, feed- 

 ing troughs, and implements used for cleaning have naturally be- 

 come contaminated with the germs of the disease, and if new stock 

 is placed in such yards soon after these were occupied by sick hogs 

 the new hogs are very likely to contract the disease, but if such yards 

 are left unoccupied the germs will die out after a while. Unfortu- 

 nately it is not possible to tell with certainty just how long a time 

 is required for these germs to die out, this uncertainty being due to 

 the fact that conditions on different farms vary widely, and also be- 

 cause the weather conditions, which have an important influence 

 upon the vitality of the hog-cholera germ, vary from time to time 

 and in different sections of the country. In view of this uncertainty 

 it is safest to wait as long as possible before placing new hogs in lots 

 that have been infected. Such premises should not be restocked 

 sooner than three months after the last pig has been removed. Be- 

 fore restocking, the premises should be cleaned and thoroughly dis- 

 infected. (F. B. 379.) 



This being a contagious disease, it follows that the germ of 

 cholera must be carried into a herd before they can contract the 

 disease. It is distributed somewhat on the same plan as are those of 

 typhoid fever, scarlet fever or diphtheria in the human race. The 

 germs are present in the blood and tissue of the affected animals, 

 and are thrown off through every avenue of the body, especially 

 through the urine and feces. In this way they infect the whole yard 

 in which the hogs are kept, and also everything in the yard and 

 pens. The smallest particle of dirt so small that it cannot be seen, 

 will carry enough germs to infect several herds of hogs. 



Conditions Favoring the Disease. These are crowding during 

 cold weather in the sleeping quarters, especially where different sized 

 animals are kept in the same pen. The smaller pigs become too hot, 

 and then very easily catch cold. Damp, filthy, dark pens where little 

 fresh air or sunshine can reach. Sleeping in a draft under buildings 

 or windows ; a pig requires twice the breathing space for every hun- 

 dred pounds of his weight that is needed by either the horse or cow. 

 Too much green corn. Too close or inbreeding. 



The accumulation of vermin on the animal itself or in the 

 pens. Too exclusive a corn diet. The hog being frequently a scav- 

 enger, following the cattle in all kinds of mud, filth and dust, is lia- 

 ble to breathe the germs of irritant dust and the lungs become in- 

 fected with tuberculosis or other debilitating disease germs. In fact 



