6i6 COMMUNICABLE DISEASES OF LABORATORY ANIMALS 



PNEUMOCOCCUS INFECTIONS 



In recent years considerable evidence has been presented that the pneumococcus 

 is a widely disseminated pathogenic organism among guinea pigs (Smith).' The 

 coccus is not only one of several factors responsible for pneumonias but it is quite 

 often associated with a number of interesting morbid changes. Aside from sporadic 

 cases observed in animals subjected to treatment or inoculation in experiments, epi- 

 demic mortalities which occur during the winter or early spring have been noted by 

 many laboratory workers. The association of a pneumococcus with an epidemic dis- 

 ease of guinea pigs was first reported by Stefanski^ in Odessa. Smith in 1914 detailed 

 his observations made in igo8 and 1909 and reviewed the outbreaks reported by 

 Selter/ Ungermann,^ Christiansen,^ and Richters,^ while Holman^ in his treatise 

 refers to papers by Tartakowsky,* Wittneben,' Salomon,'" and Kaspar and Kern." 

 To these must be added the interesting observations of Chevrel, Ranque, Senez and 

 Gruat," Freund,'^ Okamoto,'4 Branch, '^ and our own. Most of the writers emphasize 

 the localization of the lesions in the lung and the serous membranes, but Richters and 

 Okamoto encountered outbreaks in which the disease was confined to the female sex 

 organs. 



The pneumococcus which can be isolated at autopsy from the heart blood, the 

 lungs, serofibrinous exudates, middle ear, etc., is a gram positive, lancet-shaped, 

 capsulated or non-capsulated (Okamoto), bile-soluble, inulin-fermenting microbe in- 

 distinguishable from that obtained from human sources. The cultures studied in 

 different parts of the world were not agglutinated with the standard fixed types i, 2, 

 and 3 sera, although Keegan"" reported one and Stillman (quoted by Branch) identi- 

 fied several strains as type 2C. Christiansen, Gardner, place them in group 4, and 

 Branch'^ has shown that they are serologically related by their protein fraction with 

 the human strains. They are inhibited by ethyl hydrocuprein in very high dilutions 

 (i : 600,000 [Freund]). Their virulence for mice is moderate or very low (1,000,000,000 

 organisms intraperitoneally, death in two to four days [Freund and Branch]). Guinea 

 pigs may occasionally succumb to intraperitoneal and subcutaneous injections of 



' Smith, T.: J. Med. Research, 29, 291. 1913-14. 

 ^ Stefanski, V.: Ccntralbl.f. Bakleriol., 30, 201. 1901. 

 J Setter, H.: Ztschr.f. Hyg. 11. Infektionskrankh., 54, 363. 1906. 

 •I Ungermann, E.: Arb. a. d. kaiserl. Gesundheitsamte, 34, 286. 1910. 

 5 Christiansen, M.: Ztschr.f. Infektionskrankh d. Hausticre, 14, loi. 1913. 

 ^Richters, E.: ibid., p. 163. 1913. 

 'Holman, W. L.: loc. cil. 



« Tartakowsky, M. G.: Centralbl.f. Baktcriol., Orig. I, 25, 81. 1899. 

 9 Wittneben, W.: ibid., 44, 316. 1907. 

 '"Salomon, E.: ibid., 47, 8. 1908. 

 " Kaspar, F., and Kern, W.: ibid., 63, 7. 1912. 

 " Chevrel, F., et al.: Compt. rend. Soc. de biol., 82, 74. 1919. 

 '3 Freund, R.: loc. cit. 



"• Okamoto, T.: loc. cit. 's Branch, A.: loc. cit. 



'^ Keegan, J. J.: Arch. Int. Med., 26, 570. 1920. 

 "Branch, A.: op. cit., 40, 534. 1927. 



