636 COMMUNICABLE DISEASES OF LABORATORY ANIMALS 



The etiology of these localized infections has not been determined. Various 

 organisms have been cultivated from the lungs. A gram positive bacillus (Klein' 

 and Mitchell^), which at least experimentally produced on intrapleural injection a 

 pleurisy and pneumonia, a delicate Streptothrix (Tunnicliflf)/ Bad. bronchisepticum 

 (Hoskins and Stout), ^ and an organism resembling Bacillus actinoides (Jones)^ has 

 been grovm. The writer has not found the Bacillus actinoides and the gram positive 

 B. muris, but has isolated on numerous occasions streptothrices, Bad. bronchisepti- 

 cum, diphtheroids, streptococci, and fine influenza -bacillus -like rods. A few compara- 

 tive cultures of the respiratory tract of young and apparently healthy rats revealed, 

 however, a similar flora. Unfortunately, only chronic lesions which give an excellent 

 opportunity for invasion by the organisms of the upper and lower respiratory tract 

 have been examined. It is not unlikely that several types of lung disease exist and 

 that the primary injury may be due to various environmental factors which favor 

 the localization of different micro-organisms. In fact, the writer found that crowding 

 of several animals into one cage or the housing in boxes with sawdust strikingly in- 

 creased the incidence of respiratory infections. A systematic bacteriological study of 

 the rhinitis which regularly precedes the lung disease is clearly indicated. Further- 

 more, the streptothrices of the buccal cavity of rats in their relation to certain forms 

 of rat-bite fever (Schottmiiller,^ Blake, ^ Tunnicliff and Nayer,^ Ebert and Hesse^) is 

 another problem with many possibilities. 



Equally prevalent but less frequently recognized is a suppurative otitis. McCor- 

 dock and Congdon'" found pus in the auditory bulla of one or both ears in 22-50 per 

 cent of the rats examined. Many of the animals showed deafness, and the course of 

 the infection from a purulent rhinitis was traceable through the middle ear. In a 

 number of cases the two workers isolated from the nasal passages and the pus of the 

 ear a gram negative, pleomorphic, motile, short bacillus. The writer failed to cultivate 

 micro-organisms from the pus of four cases of otitis. It seems probable that the ear 

 lesions are the sequelae of the respiratory diseases which are similar to those commonly 

 observed in the rabbit. Moreover, many factors which enhance the susceptibility of 

 the rats, such as vitamin A (Daniels and Armstrong)" or mineral deficiencies (McCor- 

 dock and Congdon), increase the incidence of the "middle-ear disease" (Greenmann 

 and Diihrig). 



A pasteurellosis as described by Meyer and Batchelder'^ for wild rats has been 



' Klein, E.: Cenlralbl.f. Bakteriol., Orig. I, 33, 488. 1903. 



^Mitchell, O. W. H.: J. Infect. Dis., 10, 17. 1912. 



3 Tunnicliff, R.: ibid., 19, 767. 1916. 



■* Hoskins, H. P., and Stout, A. L. : /. Lab. 6° Clin. Med., 5, 207. 1919-20. 



5 Jones, F. S.: /. Expcr. Med., 35, 361. 1922. 



^ Schottmiiller, H.: Dermat. Wchnschr., 55, 77. 1914. 



7 Blake, F. G.: /. Exper. Med., 23, 249. 1916. 



* Tunnicliff, R., and Nayer, K. M.: J. Infect. Dis., 23, 555. 1918. 



'Ebert, B., and Hesse, E.: Arch. f. kiln. Chir., 136, 69. 1925. 



"McCordock, H. A., and Congdon, C. C: Proc. Soc. Exper. Biol. &■ Med., 22, 150. 1924. 



"Daniels, A. L., and Armstrong, M. E.: J.A.M.A., 81, 828. 1924. 



"Meyer, K. F., and Batchelder, A. P.: /. Infect. Dis., 39, 386. 1926. 



