626 COMMUNICABLE DISEASES OF LABORATORY ANIMALS 



high mortality develops among a stock of laboratory animals, it is reasonable to 

 suspect either some environmental change which affected the entire population or 

 the introduction of a very virulent strain (type D) or the sudden and wide distribu- 

 tion of virulent organisms among a susceptible population hitherto unexposed. 



These interpretations have been tested by Webster and Burn/ who have suc- 

 ceeded in maintaining a stock of rabbits free from Bad. lepisepticum infection by 

 proper attention to the "natural" resistance of the animals and by measures which 

 minimized the available dosage of the causative organisms. 



In the course of this review special emphasis has been placed on the relationship 

 of Bad. lepisepticum to snufifles and pneumonia since the studies of Webster permit 

 of no other interpretation. However, it is not unlikely that in some localities Bad. 

 hronchisepticum may assume the same role as the Pasteurella organism. Tanaka and 

 Webster produced experimentally with this organism both healthy ''carriers" and tem- 

 porary snuflfles, and several cases of pneumonia and otitis media. Sustmann^ saw 

 cases of unresolved pneumonias in chronic rabbit septicemia probably due to the same 

 organism. Of interest, however, is the fact that Bad. hronchisepticum is rarely, if 

 ever, found in the pleuropneumonic cases, and certain focalized complications such as 

 otitis media (Smith and Webster) ^ and subcutaneous abscesses (Tanaka, Meyer). 

 Furthermore, the writer has never isolated a Bact. hronchisepticum from the many 

 cases of pleuropneumonia or rabbit septicemia which developed in the course of an 

 experimental study of typhoid carriers (1917-1920) irrespective of the fact that the 

 carrier incidence of this organism was very high (plating of ground lung tissues gave 

 frequently very high counts). •* 



A perusal of the various papers leaves no doubt that a variety of bacteria with 

 bipolar granules and certain definite fermentative reactions have been isolated from 

 cases of snuffles, pleuropneumonia cases, etc. Finer distinctions were not attempted 

 until Webster and Burn^ in their papers on the biology of Bact. lepisepticum showed 

 that at least two types ("D" and "mucoid") with distinctive growth characteristics 

 and antigenic properties may be found. No cross-agglutination between the "D" 

 and "mucoid" types was demonstrable, and avirulent "G" variants were split off 

 from the original strains. Aberrant types which differ, however, from the Webster 

 types have also been isolated by Freund in Berlin. It is evident that the comparative 

 studies must be continued in various parts of the world before one can consider the 

 Bad. lepisepticum (or, according to Bergey, Pasteurella cuniculicida) a host-specific 

 micro-organism. 



The autopsy findings of fatal septicemic cases are monotonously uniform. Detailed de- 

 scription may be found in the papers by Smith,* Davis,^ Saelhof,^ Tanaka,' Webster, and 

 others. Aside from the local purulent inflammatory lesions in the nasal passages, the trachea, 

 and the bronchial tree, confluent areas of bronchopneumonia sometimes including whole 



' Webster, L. T., and Burn, C: /. Expcr. Med., 45, 911. 1927. 



= Sustmann, H.: Tierarzll. Riindsch., 21, 21. 1915. 



3 Smith, D. T., and Webster, L. T.: loc. cit. 



1 Meyer, K. F., Neilson, N. M., and Feusier, M. L.: /. Infect. Dis., 28, 410. 1921. 



5 Webster, L. T., and Burn, C. G.: op. cit., 44, 343 and 359. 1927. 



^ Smith, D. T.: loc. cit. » Saelhof, C. C: loc. cit. 



7 Davis, J. D.: loc. cit. 'Tanaka, A.: loc. cit. 



