556 IOWA DEPARTMENT OF AGRICULTURE 



showing circumscribed or diffused ulcers in mucosa of the stomach, button 

 like ulcers in the colon, inflammation of the entire intestinal tract 

 and ulcers at the ileo caecal valve, the latter being the most certain path- 

 ognomic lesion in hog cholera. In general outbreaks the most acute 

 types are seen at first, followed by the less acute and sometimes the 

 chronic form. The infection on being passed from one animal to another 

 gradually becomes weakened. Mortality varies from 70 to 100 per cent. 



CAUSES. 



Until recent years the bacillus cholera suis has been accepted as the 

 specific cause of hog cholera. The work of De Schweinitz, Dorset, Mc- 

 Bride and Niles proved the hog cholera bacillus to be a secondary in- 

 vader and the ultimate primary cause was an invisible, ultramiscros- 

 copic micro-organism, a virus in the blood and excretions of the latter, 

 the urine in particular. If the cause is a germ, it is so small, or per- 

 haps unstainable, and the strongest microscopes will not detect it. After 

 removing the bacillus cholera suis by passing through a porcelain filter, 

 the filtrate when introduced subcutaneously seldom produced the dis- 

 ease, but on intravenous injections of the same cultures, occasionally 

 resulted in death. 



Schreiber considers the toxin formed by the hog cholera bacillus as 

 the exciting cause or that the ultra microscopic virus is an excretion of 

 the true bacillus of hog cholera. Hutyra considers the virus respon- 

 sible not only for the so called hog cholera but for the swine plague as 

 well. In conclusion it has been generally accepted that the ultra-micros- 

 copic micro-organism or virus is the primary cause, and the bacillus 

 cholera suis a secondary invader. 



PREDISPOSING AND ACCESSORY CAUSES. 



Anything which lowers the vitality of animals renders them more sus- 

 ceptible to disease upon being exposed. For example, improper feed, 

 a one-sided ration of corn, so common in corn raising districts, impure 

 water from stagnant pools and poorly drained hog lots, unsanitary, ill- 

 ventilated houses, filthy troughs, buckets and slop barrels. These things 

 in themselves do not cause cholera, but they render an animal less resist- 

 ant and therefor an easy victim upon being exposed. 



Pens and houses in which cholera hogs have died should be considered 

 infected. The feces and urine passed by the sick animals may contain 

 the germ and be carried to all parts of the lot on the feet of healthy 

 hogs, or by the attendant from one pen to the others. Anything which 

 tends to scatter dirt, manure, water or feed from infected pens as birds, 

 rats, dogs or streams can spread the disease. Buying of hogs from 

 recently infected herds may spread the disease and should be guarded 

 against. Hogs which are shipped should especially be considered as a 

 source of infection, as stock yards, highways and stock cars are often 

 used to convey and shelter cholera hogs without a subsequent disinfec- 

 tion. 



