ENZOOTIC DYSENTERY 57 



every instance it attacks every cow, calf and bull on 

 the premises; only in rare instances do any mem- 

 bers of the herd escape the infection. To the veter- 

 inarian who has had no experience with this disease 

 this peculiarity usually leads him to assume that the 

 cause of the outbreak can be attributed to food con- 

 tamination. That he is mistaken in this assumption 

 he discovers later when he finds the disease on other 

 farms, sometimes miles away, where entirely different 

 feeds and water, and entirely different methods of 

 feeding and watering are used. 



In many instances it is no difficult matter to trace 

 the infection carrier, from one farm to another, in 

 the person of visitors, stock-buyers or others. 



In other respects, also, the disease has the ear- 

 marks of an infectious disease; the symptoms are al- 

 ways the same, the color of the feces is always the 

 same, and the course of the attack varies but slightly 

 in any instance. Another point indicating an infec- 

 tious character in this disease is the fact that towards 

 the latter part of an outbreak the cases are milder; 

 this is characteristic of many epidemic and epizootic 

 diseases. 



Enzootic dysentery is serious because it runs a rath- 

 er slow course, during which the secretion of milk is 

 almost entirely stopped. We recall an instance in 

 which a herd of fifteen cows altogether gave less than 

 an ordinary milk pail full of milk at one milking. 

 Deaths occur but rarely; in two outbreaks we remem- 

 ber but a single death in each, although hundreds of 

 cows were affected. 



The symptoms of enzootic dysentery can not be 

 mistaken easily for those of other forms of dysentery. 

 The attack begins on a farm, usually, with one or two 

 cases. A cow refuses her feed and it is seen that she 



