620 COMMUNICABLE DISEASES OF LABORATORY ANIMALS 



possible occurrence of variants of lost pathogenicity was not considered nor investi- 

 gated. These findings are fully in harmony with those made by Meyer and Batchelder 

 in the course of an investigation which dealt with a similar infection of wild rats. In 

 this connection it is recalled that the epidemic "body strain" was fully capable of caus- 

 ing active, rapidly fatal infections without any contributory factors which would in- 

 crease the susceptibility of the host. As soon as the individuals of low resistance had 

 been weeded out, the invading organism adjusted itself to the rat population on a low- 

 ered level of virulence or disappeared entirely from the nasal passages and the bron- 

 chial tree. It seems probable that the observations reported by Freund on guinea pigs 

 are entirely analogous. A long-continued and extensive prevalence of highly virulent 

 pasteurella organisms produced contact infections, a large number of fatalities but 

 few cases of rhinitis and carriers. The experiments of Uchida, which are used by 

 Freund to support his contention that thermal or other factors were necessary to 

 provoke the pasteurella epidemic observed by him, were made with cultures and not 

 with "body" strains and on guinea pigs of an infected population. It is therefore 

 reasonable to suppose that in the pasteurella infections observed by Freund the 

 microbic virulence played a greater role than the host factors. 



STREPTOCOCCUS INFECTIONS 



In 1907 Boxmeyer^ noted in a caviery belonging to a western antitoxin manu- 

 facturer three thousand guinea pigs with enlarged, abscessed lymph nodes of the neck 

 and axilla. He isolated from the lesions a |3 hemolytic streptococcus. The disease, 

 known as "epizootic lymph adenitis" and in all probability a wound infection, was 

 spread by the pus that escaped when the abscesses ruptured externally or when the 

 virus entered a new host through small abrasions of the upper digestive tract. An 

 identical disease was seen by the writer in 191 7 in twenty- two guinea pigs of a ship- 

 ment from a dealer in California. The /3 hemolytic streptococci resembled Sir. 

 pyogenes in their carbohydrate reactions; agglutination tests were not made. Young 

 and full-grown guinea pigs were infected by contact through bite wounds. According 

 to Altana,^ Kaspar and Kern,^ Micrococcus tetragemis may cause a similar contagious 

 disease among laboratory guinea pigs. 



TUBERCLE-BACILLUS INFECTIONS 



The significant observations of R. Koch^ that guinea pigs exposed in the same 

 room with tuberculous animals for a longer period than four months may not infre- 

 quently develop spontaneous tuberculosis have not been adequately appreciated by 

 laboratory workers. Romer,^ Roos,** Distaso,^ and in particular Feyerabend** have 

 reported isolated spontaneous cases or group infections with the tubercle ba- 



' Boxmeyer, C. H.: J. Infect. Dis., 4, 657. 1907. 



= Altana, G.: Centralbl.f. Bakleriol., Orig. I, 48, 42. 1909. 



3 Kaspar, F., and Kern, W.: loc. cit. 



'•Koch, R.: Gesammelte Werke von R. Koch, i, 512. Leipzig, 1912. 



5 See Steinmetz, M., and Lerche, P.: in op. cit., 100, 127. Hannover, 1923. 



••Raebiger, M., and Lerche, M.: op. cit., 21, 687 and 688. 1926. 



'Distaso, A.: Conipt. rend. Soc. de bioL, 79, 119. 1916. 



* Feyerabend, O.: Beitr. z. Klin. d. Titberk., 39, i. 1913. 



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