farmers' institutes. Y31 



pie, ma J' be caused by a change of food, l»y gieeii food, by spoiled food. 

 by watering when the animal is too warm, by contaminated water, by 

 drugs, by exhaustion, by exposure, l)y worms and other causes. 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 any organism acting. If several 

 other animals are affected alike at the same time it is beeaiise .ill have 

 been subject 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 rtock 

 are affected at the same time, and there is no tendency to spread. 



Contagious diseases are those which are always produced by the same 

 cause and the causative factor may be communicated from one animal 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 par- 

 asitic and do not live or multiply outside the body, and which require 

 comparatively close contact in order to spread. Distance or a long lapse 

 of time between the coming of animals to the same place are sutticient 

 to prevent the spread. In other words tlie germ does not pass an in- 

 definite distance between the animals or live for a long time outside the 

 animal's body. As examples of this 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 dis- 

 eased sheep may come in contact for a long time. Therefore sheep sep- 

 arated by a roadway, or flocks using the pens where diseased slieep have 

 been some months prior do not become affected. Pleuro-pneumonia In 

 cattle is also a contagious disease, and at one time had a good foothold in 

 this country. It is a disease in which the germ does not live long out- 

 side the body and only carried by contact or artilicial means. It was 

 eradicated by destroying all that were affected and disinfecting the 

 places where it had been. Glanders among horses is also contagious, as it 

 is only spread liy contact or close association. All strictly contagious 

 dis(»ases are controllable and could be exterminalcd by united efforts. 

 The drastic measures used to stamj) out pleuro-pncunioni.i would stanii> 

 out sheep scab in a short time. 



Infectious diseasesaro those caused by some sijccial agfiii or ]iarasire, 

 and the cause may live and multiply outside tlie body. Infectious dis- 

 eases maj' be and frequently are contagious. Some infectious diseases, 

 however, are not contagious. The line separating contagious and in- 

 fectious diseases is not very clear. The distinction is largely one of de- 

 gree. Among the types of infectious diseases we have lump Jaw and 

 blackleg of cattle, distemper and influenza of horses, cholera and swine 

 plague in hogs, and roup in poultry. True lump jaw in cattle is always 

 caused by the ray fungus. Tlic fungus is olitainod uimn the food which 



