38 JOHNE'S DISEASE 



Britain, the question of a certain means of diagnosis is 

 now of great importance. Recently the case of a 

 warranted cow developing Johne's disease within a 

 month of sale has been the subject of legal comment 

 in an agricultural newspaper. 



As a rule the attention of a practitioner is called to 

 a cow in poor condition which is suffering from diar- 

 rhoea, and there may be a history of other animals 

 having been similarly affected during the past year. 

 If he applies the ordinary tuberculin test with a nega- 

 tive result, the suspicion of Johne's disease is certainly 

 increased, and the faeces should then be examined for 

 acid-fast bacilli. 



Meyers procedure is probably the best A small 

 quantity of liquid faeces should be placed on a flat 

 dish, and in this thin layer it may be possible to see 

 small shreds of mucus. The blade of a small knife 

 may then be passed through the flame of a spirit-lamp 

 and a piece of mucus picked out and rubbed over the 

 centre of an ordinary glass microscope slide. The 

 film is dried and stained by Ziehl-Neelsen's method 

 (p. 64). The presence in such a film of acid -fast 

 bacilli in every way resembling Johne's bacillus is 

 strong evidence that the animal in question is suffer- 

 ing from Johne's disease; but there are acid-fast bacilli, 

 such as dung bacilli (mist bacillus of Moeller) and the 

 timothy-grass bacillus, which may easily be mistaken 

 for the bacillus of pseudo-tuberculous enteritis. 



A better method is to take scrapings from the rectal 

 mucous membrane or to pinch off a small portion of 

 this with the finger-nails by inserting the arm into the 

 rectum, since the bacilli so found are more likely to be 

 the specific infecting micro-organism. The latter pro- 

 cedure, however, is open to the objection that although 

 films made from the walls of the ileum and caecum and 



