272 VETERINARY HYGIENE 



Cooledge* in America found that 27 per cent, of the cattle on 7 farms 

 were passing abortion bacilli in the milk. He further states that 

 the milk may remain a carrier for years. The disease is thus as 

 a rule introduced into healthy herds by an infected cow which at 

 the time of abortion becomes an active centre of infection. From 

 this centre infection may spread through the agencies above men- 

 tioned, and in addition may be conveyed to other animals by 

 attendants, grooming tools, &c. The disease is enabled to establish 

 itself in a herd owing to its insidious nature, and to the fact that 

 the infectious nature of the trouble is not realised until some months 

 later when several other pregnant animals abort. The mortality 

 from the disease itself is nil, but deaths may follow as the result 

 of such sequelae as retention of placenta which commonly occurs. 



It is not an easy matter to fix the period of incubation. Taking 

 this as the period between the moment of infection and the act of 

 abortion which, as before stated, does not always occur, it may 

 be as short as a month or a good deal longer. In Bang's experi- 

 ments in which cows were fed with culture or exudate, abortion 

 occurred after one to two months, f According to Hutyra and 

 Marek$ abortion in the cow generally takes place in the fifth or 

 sixth month of pregnancy. 



PREVENTIVE MEASURES. The Departmental Committee 

 appointed in 1905 to report on the disease recommended compulsory 

 notification of cases of abortion and veterinary inquiry to establish 

 the existence of the disease, together with temporary isolation and 

 restriction of movement of recently aborted cows and measures 

 to prevent the importation of cases from abroad. Opinion to-day 

 is rather at variance with these recommendations since the disease 

 has become more widespread, and since more recent discoveries 

 have pointed the way to methods of prevention which are unlikely 

 to cause so much interference with cattle breeding. 



Stockman, in his report to the Tenth International Congress, 

 states : " Having regard to the facts that the disease prevails in 

 an enormous number of dairy herds, and that a very high propor- 

 tion of the animals are affected, state measures which are based 

 on effective restrictions on the movement of infected animals would 

 be ruinous to the business of farmers, while partial measures of the 

 same kind are not worth the expenditure which would be incurred 

 owing to administration. It is more than questionable, even assum- 



*Journ. Med. Res., Vol. XXXVIL, No. 2, November, 1917, 

 pp. 207-214, through Vet. Rev., Vol. II., No. 2, May, 1918, p. 168. 



f Hutyra and Marek, Spec. Path., Vol. I., p. 741. 

 $ Hutyra and Marek, Spec. Path., Vol. I., p. 744. 



