PART II 



DISEASES OF SWINE. 



KINDS AND CAUSES OF DISEASE. 



AS A MATTER of convenience and to aid in understanding dis- 

 eases, they are here divided into three classes: (1) sporadic, 

 (2) contagious, and (3) infectious. Thiis classification 

 is purely arbitrary and is based upon the nature of the cause. 



It is believed that this classification will be better understood 

 than those given by many writers whose arrangement is more 

 complex. 



Sporadic. Sporadic diseases are those which have no one con- 

 stant cause. A variety of causes may produce the same disease. 

 Colic, diarrhoea, rheumatism, colds, etc., are types of sporadic dis- 

 eases. Colic for example may be caused by a change of food, by 

 green food, by spoiled food, by watering when the animal is too 

 warm, by contaminated water, by drugs, by exhaustion, by exposure, 

 by intestinal worms, etc. There is no single cause for colic, colds or 

 any other sporadic disease. In sporadic diseases, the disease can not 

 be conveyed from one animal to another as there is no specific germ 

 or other organism acting. If several animals are affected alike at 

 the same time, it is because all have been subjected to like causes 

 and not because it has spread from one to another. As a rule, only 

 one or a few animals of a stable, herd or flock are affected at one time 

 and there is no tendency to spread. 



Contagious Diseases. These are always produced by the same 

 cause, and the causative factor may be communicated from one ani- 

 mal to another of the same species, or in some cases to animals of 

 different species. When we speak of strictly contagious diseases, we 

 usually have reference to those due to germs, or animal life that 

 are normally parasitic and do not live or multiply outside the body, 

 and which require comparatively close contact in order to spread. 

 Distance, or a comparatively short time between the coming of 

 animals to the same place are sufficient to prevent the spread. In 

 other words, the germ does not pass an indefinite distance between 

 the animals or live for a long time outside the animal's body. As 

 examples of this type of disease, we have sheep scab, tape worms, 

 glanders, pleuro pneumonia, etc. In the case of sheep scab the 

 cause is always the scab mite; it can not travel alone and will not 

 live in the pens, in the cars, on the fences or other objects with 

 which the diseased sheep may come in contact for a long time. 

 Therefore sheep separated by a roadway, or flocks using the pens 

 where diseased sheep have been some months prior do not become 



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