400 Contagious Pleuro-pncuinonia. 



As an epizootic contagious pleuro-pneumonia usually runs 

 a slow course. After the first introduction the suspicion of 

 a general outbreak, because of its occurrence in several animals, 

 is aroused only after about 4 to 6 weeks. In stables the imme- 

 diate neighbors of the affected animal become first affected, and 

 the number of cases increases only from week to week, so that 

 in large herds it requires several months before all susceptible 

 animals are affected. If the dead or emergency slaughtered 

 animals are replaced by new ones, as for instance in fattening 

 establishments, the disease may exist with varying intensity for 

 years, and it may also be propagated for years among animals 

 in a township when kept upon public pastures. 



Diagnosis. In the living animals a positive diagnosis can 

 only rarely be made with sufficient assurance. Physical exam- 

 ination shows only that the animal is affected with pneumonia, 

 or pleuro-pneumonia, the nature of which however can be estab- 

 lished accurately only by reliable historical data. If there is 

 a suspicion of infection every disease of the lungs which shows 

 a latent development and which gradually becomes more inten- 

 sive is a suspicious indication of the disease, especially when 

 several cattle become affected successively under similar mani- 

 festations. Under such conditions the diagnosis of contagious 

 pleuro-pneumonia may be established with great probaljility, 

 especially when the disease becomes more advanced, and the 

 symptoms become more pronounced. Absolute certainty how- 

 ever is even in such cases revealed only by the autopsy. 



From the standpoint of differential diagnosis, the subacute 

 pectoral form of hemorrhagic septicemia comes into consider- 

 ation in the first place. Although in most cases it is distin- 

 guished from pleuro-pneumonia by the sudden onset, the acute 

 course, the severe intestinal inflammation which is commonly 

 present, as well as the simultaneous affection of several animals, 

 isolated cases of the disease which run a slower course may be 

 easily mistaken for the acute stage of pleuro-pneumonia. The 

 diagnosis is sometimes difficult even on postmortem examin- 

 ation ; although in hemorrhagic septicemia a larger part of the 

 lung is usually uniformly affected and the cut surface shows no 

 marbled appearance, yet the changes in the lungs may entirely 

 simulate those of acute pleuro-pneumonia. Numerous hemor- 

 rhages in the pleural tissue and in the mucous membrane of 

 the air passages are indications of hemorrhagic septicemia, 

 nevertheless even in such cases the diagnosis can be established 

 with certainty only by bacteriological examination. In this 

 respect the difference is that in pleuro-pneumonia the exudate 

 of the lungs reveals no bacteria under the microscope, further 

 the inoculation of the fluid from the lungs has no etfect on test 

 animals, and in calves the subcutaneous injection is followed 

 after one week at the earliest by an edematous swelling, while 

 in hemorrhagic septicemia the exudate of the lungs contains 

 small, polar stained bacilli ; the inoculation of the fluid from the 



