1909.] Report on Epizootic Abortion. 



479 



act is also virulent. It is possible that the dung of an 

 animal which has ingested infective material may be virulent 

 for a time. It is improbable that abortion bacilli are excreted 

 in the milk of affected cows. 



The length of time during which the virulent materials may 

 remain infective outside the animal is of considerable import- 

 ance, and it appeared from the experiments that virulent 

 material may, if kept fluid and free from putrefaction, remain 

 infective for seven months, but not for a year. Observations 

 on this point are being continued. 



Methods of Infection. — Once the contents of the uterus 

 have been expelled the virulent material may be carried to 

 other parts of the cowshed along the surface drains, and may 

 be transported long distances in the soiled manure, on the 

 coats of the aborting animals and their companions, on the 

 hands and boots of attendants, and also by dogs and other 

 animals. Cows which have aborted must also be considered 

 sources of infection so long as the discharge continues to 

 come from the genital organs, and it may continue inter- 

 mittently for a few weeks if the animals be not treated. Such 

 animals, if not isolated, may continue to infect the sheds, or 

 the pastures when turned out to graze. 



From these sources fresh animals may be infected, and 

 there are two ways in which the virulent material may gain 

 access to the pregnant uterus, viz., by the vagina and by 

 the mouth. With regard to infection by the mouth, this 

 is a natural method of infection which until recently did 

 not enter into anybody's calculations regarding the spread of 

 abortion, and as the food, including the pastures, and even 

 the feeding trough, may more or less easily be contaminated 

 on an infected establishment, it seems highly probable that 

 infection by ingestion often takes place. In fact, the Com- 

 mittee are inclined to believe that the disease is more 

 frequently contracted in this way than in any other. 



Infection by the vagina has always been supposed to 'be 

 the most frequent natural method, partly because it was 

 thought that the gutter which in most cowsheds runs behind 

 cows standing in line often brings the discharges from an 

 aborting cow in contact with the tails and external genital 

 organs of her .companions. In considering the relative 



