INFECTIOUS DISEASES OF MICE 433 



tions have been found by various investigators, but the detailed work of 

 Schockaert (240, 241) indicates that virulence varies regardless of source and 

 that the human, rat and mouse strains constitute a single species. Human 

 cases resulting from the bite of a mouse (in, 115, 217), or from inoculation 

 of a mouse strain of the spirillum (131, 240), are indistinguishable clinically 

 from those due to human or rat strains. 



Recovery from infection and disappearance of the organisms in mice 

 probably is due to an immunological mechanism. Although lytic antibodies 

 have never been satisfactorily demonstrated in mice, active immunization 

 to homologous and heterologous strains does occur. Arsenic preparations, 

 such as arsphenamine or neoarsphenamine, are effective in treating human 

 infection and might be tried if it were desirable to rid infected mice of the 

 organisms. 



Leptospira icterohemorrhagiae.* — Following the identification of Lepto- 

 spira ictcrohcmorrhagiae as the causative agent of infectious jaundice (Weil's 

 disease) and its demonstration in rats, Miyajima [quoted by Ido, et al. (108)] 

 found the organism on several occasions in the kidneys of the field mouse, 

 Microtus montehelloi. The leptospira was subsequently found in i of 6 field 

 mice (108), and in i of 2 field mice but not in 2 house mice from the Edin- 

 burgh area of Scotland (38). Packchanian (193) has recently reported the 

 occurrence of Leptospira icterohemorrhagiae in laboratory white mice {Mus 

 musculus) and the susceptibility of certain species of American deer mice 

 {Peromysciis) to experimental infection. White mice ordinarily show no 

 signs of infection. Inoculation of infected mouse blood or tissues into 

 guinea pigs or American deer mice, however, results in fever, jaundice, 

 hemorrhages, and death. The organisms are demonstrable in the blood and 

 urine. 



Morphologically, Leptospira icterohemorrhagiae is a delicate organism 

 having closely wound, rigid spirals and secondary wavy curves. It varies 

 from 0.1 to 0.2 ^^ in width and from 6 to 12 ^t in length, occasional specimens 

 being as long as 25 /x. The organism is flexible and one or both ends may be 

 curved or hooked, giving an S or C shape. During movement, the hooked 

 ends whirl around rapidly. Darkfield examination and silver impregnation 

 are best for demonstration of the organism. Bile salts (10 per cent) but not 

 saponin dissolve it. Cultivation may be effected in dilute serum media at 

 25°C. 



* Sellards (248) has recently proposed Leptospira interrogans as the correct name 

 for this organism. 



