EXPERIMENT STATION BULLETINS. 325 



INFECTIOUS ABORTION IN CATTLE. 



Circular No. 29. 



INTRODUCTION. 



In Michigan we consider infectious abortion one of tlie three in- 

 fectious diseases (hog cholera, tuberculosis, infectious abortion) of 

 greatest importance and gravest danger to the industry of animal hus- 

 bandry in this section of the country. Our experiences gained by con- 

 versation, correspondence and personal inspections, indicate that in- 

 fectious abortion is distributed throughout the state in the pure bred 

 herds especially, but also in herds without breeding. It is found in pub- 

 lic institutional and in private herds where sanitary conditions are 

 nearly ideal and in herds kept under very insanitary conditions. Its 

 greater prevalence in pure bred herds is not due to their breeding, but 

 to the greater and more widespread traffic in such animals. 



There is a popular and urgent demand from all parts of the state for 

 information relative to this disease and in an effort to satisfy this de- 

 mand we are presenting the facts concerning the disease as they now ap- 

 pear to us. We must confess an ignorance of many features of the dis- 

 ease and an inability to outline any entirely satisfactory plan of con- 

 trol. Many European and American investigators are studying the 

 various phases of the disease with the one object of discovering some 

 means of control. However, knowledge of a definite and practical na- 

 ture which can be effectively applied must be expected to come slowly. 

 From a careful study of all the available literature and from our own 

 observations we are presenting that which to us appears the best. 



MEANS OP DISSEMINATION. 



Affected cows. A common way in which the disease is introduced 

 into the herd is through the purchase of an affected female animal. She 

 may be an apparently healthy cow, either with calf or non-pregnant. If 

 affected, such a cow may become a source of infection at the time she 

 calves and remain so until the uterus is free of the disease or until the 

 cow again becomes pregnant. During pregnancy we do not know 

 whether an affected animal eliminates the infectious organism through 

 the genital passages, but we are inclined to believe they do not. Just 

 how long an affected cow will continue to discharge from the vagina the 

 infectious material after an abortion or a normal parturition we do 

 not know, but it is known that the cow may excrete the abortion germ 

 for years in the milk. 



The hull. The bull may carry the infection from one animal to an- 

 otlier. The bull does not necessarily become affected with the disease, 

 but through contamination of the penis and shealli with the discharges 

 of an affected cow he is able to convey the disease to other animals. 



