PREVENTIVE MEDICINE 275 



Stockman therefore doubts " whether the infection in connection 

 with ovine abortion is in reality kept up mainly owing to a sapro- 

 phytic existence on the part of the vibrio." 



PREVENTIVE MEASURES. The most certain method of prevent- 

 ing the spread of the disease is to make it compulsory that breeding 

 stock is sold only on a guarantee that the flock is free from infection. 



EQUINE ABORTION. 



This is a contagious disease due to a specific organism belonging 

 to the para-typhoid group and called the Bacillus of equine abortion 

 or Bacillus abortivo-equinus. Though some observers abroad 

 (Ostertag and others) have considered that streptococci are the real 

 cause, the researches of M'Fadyean and Edwards* have shown that 

 the paratyphoid bacillus mentioned is responsible for a large pro- 

 portion of cases of abortion in this country, and for some cases of 

 joint-ill occurring in foals shortly after birth. The same organism 

 had previously been isolated in the course of outbreaks by other 

 workers abroad (Smith and Kilborne, de Jong, &c.). The disease 

 has probably existed in this country as an enzootic since an early 

 date, but though still present and the cause of considerable losses in 

 parts of Great Britain it has not attained the same ubiquity as 

 bovine abortion owing to the fact that traffic in mares is much less 

 than with cows. Though natural cases of infection by this organism 

 only appear to occur in the mare and foal, abortion has been pro- 

 duced by inoculation into the pregnant cow, ewe, goat and sow. 

 Outbreaks have been described in donkey studs (Clive Webb)f 

 and the same organism has been isolated from one such outbreak 

 by Good and Corbett in North America. According to DesoubryJ 

 abortion may occur at almost any period of gestation. The natural 

 method of infection is probably by ingestion of food or water con- 

 taminated with virulent discharge, though it should be remembered 

 that the stallion may play a part in the spread of the disease. De 

 Jong was successful in infecting one mare by feeding with artificial 

 culture mixed with food, abortion occurring in this animal on the 

 twelfth day. The period of incubation has been fixed at about 15 

 days. The disease is spread from one part of the country to 

 another in the same way as bovine abortion, i.e., by the sale of 

 recently aborted mares or infected pregnant mares which are appar- 

 ently healthy. It is not certainly known how long the organism can 

 * Journ. Comp. Path., 1917, Vol. XXX., p. 331. 

 t Journ. Comp. Path., 1909, Vol. XXII., p. 289. 

 t Journ. Comp. Path., 1909, Vol. XXII., p. 154, Trans. 



