264 DISEASES OF SWINE- 



those visited by the pigeons, however, in their daily flights. It was 

 not long after the animals began dying on this first farm that the 

 disease made its appearance on the farm which served as the home 

 roost for the pigeons. In the course of a month it was quite widely 

 scattered through the neighborhood, and a noteworthy fact about 

 this outbreak was that those farms which became infected first 

 were those which were in the habit of being visited by the flock of 

 birds just mentioned. As there was no direct communication of 

 any other sort between these various farms, and every care was 

 taken in the burning of dead animals, the conclusion must, of neces- 

 sity, be drawn that the most important cause for the spread of the 

 disease was these pigeons. 



In connection with this outbreak it is worthy of mention that 

 the source of the outbreak on the first farm was the shipping in from 

 Wisconsin of a boar which had been guaranteed as immune to 

 cholera, as he had already been through an attack and had appa- 

 rently entirely recovered. The after-results, however, would 

 make it seem that this boar was one of those cases which I have 

 already described, known as "carriers." 



These carriers are animals which are throwing off hog-cholera 

 germs in their manure and urine, but who do not themselves show 

 any evidences of the disease. Unfortunately, we have no practical 

 way of determining which animals are "carriers" and which are not. 

 In a general way it may be stated that animals which have suffered 

 from a chronic form of the disease are more likely to afterward 

 prove to be "carriers" than those which have been affected by the 

 acute type. 



There was another occurrence in this outbreak that is well worth 

 mentioning. All the farms on which the disease made its appear- 

 ance were owned by men who were quite well posted along the 

 fines of prevention of cholera. Many of them were men who had 

 attended the Agricultural Department of the State University, 

 and every precaution was taken to prevent the scattering of the 

 disease. All the dead animals were promptly burned or buried in 

 quicklime and crude sulphuric acid. As a result, there was not a 

 single buzzard seen in the vicinity during the entire time the out- 

 break was in progress, and the disease reached only one or two farms 

 where its course could not be traced to the daily flights of the flock 



