PATHOGENICITY AND EXPERIMENTAL INFECTION OF ANIMALS 429 



TABLE 27 

 Showing the Susceptibility of certain Animals to Experimental Infection 



WITH THE FOUR MAIN TyPES OF TUBERCLE BaCILLI. 



Susceptible to 



Species of Animal. 



Severity of Disease caused by Types of 

 Tubercle Bacilli. 



Human. 



Bovine. 



Murine. 



General infection 

 by bovine type 



Ox, goat, cat .... 



Pig 



Horse (a) 



Rabbit (b) 



Vole(d) 



Guinea-pig (6) . . . . 



Dog (a) 



Anthropoid apes and other 

 monkeys 



Other wild animals in cap- 

 tivity 



Rat (c), mouse (c) . 



Golden hamster 



Parrot, cockatoo, and 

 canaries (/).... 



+ + + 



+ + + 



+ 



+ + + 



+ + + 



± (calf) 



± 

 + + 



± 

 ± 

 



+ Y 

 ± 



Infection by both 

 bovine and 

 human types 



+ + + 

 ± 



+ + 



+ + 

 + + Y 



+ + + 

 + + 



+ + + 

 ± 



+ + 



+ + 

 + + Y 



+ + 

 + + 



+ + Y 

 + (e) 



+ Y 

 







? 



+ Y 

 + Y 



+ + 



Insusceptible to 

 mammalian types 



Fowls and other domestic 

 birds 



+ + 



^ A local retrogressive lesion. 



± Localized tuberculosis, with sometimes slight dissemination. 



-f , -\ — |-, -| — I — \- DifTerent degrees of progressive tuberculosis. 



+ Y Tuberculosis of the Yersin type. 



(a) Spontaneous tuberculosis relatively uncommon ; difficult to infect experimentally. 



(6) Extremely easy to infect experimentally, but seldom contracts tuberculosis naturally. 



(c) Spontaneous tuberculosis is rare ; after intravenous inoculation mice die with mihary 

 tuberculosis of the lungs and an enlarged spleen containing tubercle bacilli in great numbers. 



(d) Spontaneous infection with the murine type appears to be common. The natural disease, 

 and the experimental disease caused by the murine type, are characterized by tuberculosis of 

 the lungs and lymphatic system, and the occurrence of necrotic or caseous material in the 

 subcutaneous areolar tissue reminiscent of rat leprosy. Experimental infection with the bovine 

 type gives rise to acute generalized tuberculosis. 



(e) Produces slowly progressing generalized tuberculosis without necrosis or caseation of 

 the lesions. 



(/) Canaries are said to be less susceptible to infection with the human and bovine types 

 than parrots and cockatoos (Tulloch 1936). 



into laboratory animals, or even into larger animals such as calves, may give rise 

 to severe illness, sometimes followed by death (Kossel et al. 1904, Twort and Craig 

 1913). The bacilli do not multiply in the tissues, and therefore no true infection 

 is set up ; the symptoms appear to be due to toxaemia following the liberation of 

 endotoxins from the bacilli in contact with the tissues. Similar results can be 

 obtained with dead bacilli. This toxaemia following the intravenous injection of 

 living or dead acid-fast bacilli, whether of the saprophytic acid-fast or the true 

 tubercle type, into susceptible animals, is a phenomenon that may lead to confusion 

 if differentiation of the various types is attempted by the intravenous route. For 

 this reason the subcutaneous method of injection is generally to be preferred. 



