EXPERIMENT STATION BULLETINS. 493 



it is evident that in order to have an attack of hog cholera the virus of 

 the disease must be introduced iuto the herd in some manner. A study 

 of some of the ways by which the virus is carried from place to place 

 will better enable us to understand how to prevent the disease. 



The air is a medium by which the germs of most diseases pass from 

 place to place and so it is in hog cholera and the spread of the disease 

 in this way is hard to hold in check. Streams furnish a means of con- 

 veying the virus from place to place. The water of an entire stream 

 is often polluted by hog cholera in some herd which has access to it. 

 Ponds, especially if fed from streams from other farms, are a source 

 of contagion. Dogs and other small animals, that roam at will, may 

 carry in the dirt upon their feet the virus, if it so happens that they pass 

 through a yard or field where an affected herd is kept, or if they find 

 the carcass of an animal which died from the disease and has carelessly 

 been left lying where they can get at it. Crows and other carrion birds 

 may also be the means of conveying the disease in the same way. Buyers 

 going from drove to drove, or visitors, may spread the disease. The 

 introduction of new stock into the herd is always fraught with more 

 or less danger, especially if they have been shipped on the railroad. All 

 new stock should be quarantined upon another part of the farm for 

 five or six weeks before placing them in the herd. Railroads spread the 

 disease by carrying infected animals. For this reason fields bordering 

 upon railroads may be looked upon with suspicion for the pasturing 

 of hogs. 



The time elapsing after the animals are exposed, or the germs are in- 

 troduced into the herd, before the disease manifests itself, varies from 

 four or five days, to three or four weeks. 



SYMPTOMS. 



The symptoms of hog cholera are somewhat variable. In some cases 

 it takes a very acute form, the animals living only a day or so; while at 

 other times it may run a lingering course of three or four weeks. In 

 some outbreaks quite a large per cent of the cases will recover; while 

 at other times nearly every animal affected will succumb. At times 

 those that recover will do well, growing and fattening nicely, and again 

 thev will seem to be stunted and never amount to much. 



Generally the first symptom noticed is that the animal refuses his 

 feed to a greater or less degree. There is apparent weakness of the 

 hind limbs, arching of the back and a drawing up of the abdomen; shiv- 

 ering is also noticeable. The animal manifests a desire to bury him- 

 self in the litter, or if there are a number they will huddle together. 

 Oftentimes red spots or blotches will appear on the surface of the skin, 

 especially on the abdomen, ears and inside of the legs. There is more 

 or less fever, indicated by a rise of temperature, the normal temperature 

 of the hog being about 102°. At times more or less coughing is present; 

 this symptom being more noticeable in swine plague than in hog cholera. 

 There is a discharge from the eyes, at first watery, later becoming thicker 

 and tending to cause the eyelids to adhere to each other. At the begin- 

 ning of the disease the bowels may be normal, or they may be consti- 

 pated; but as the disease advances there is apt to be an offensive diar- 



