50 



The English Plague Commission observed the disease in India in 

 1907 (Wherry). 



Wherry (1908) and McCoy (1908) report upon the finding of the 

 disease in rats caught in San Francisco, Cal. 



Mezincescu (1908) has studied the disease and attempted to deter- 

 mine its relationship to known human lepra by complement fixation 

 tests. 



DESCRIPTION OF DISEASE. 



Geographical occurrence. It would be premature at present to 

 make didactic statements as to the geographical distribution of the 

 disease, for its discovery has usually depended upon antiplague 

 measures, which are not world- wide in their scope. In spite of 

 this it seems profitable to briefly review the known occurrence of 

 the disease in relation to that of human leprosy. When such a 

 comparison is made we note that the disease is present among the 

 rats of Berlin, a city which is practically free from human lepra. 

 On the other hand in Honolulu, which is an endemic focus of human 

 leprosy, in the examination of 16,000 rats, during an antiplague cam- 

 paign, no case of rat leprosy was encountered. In addition to the 

 scrutiny of the rats examined for plague in Honolulu, an attempt 

 was made to obtain leper rats by offering a reward for a rat, dead 

 or alive, infected with the disease. This offer was given wide pub- 

 licity in the Territory, but brought no results. 



Occurrence of the disease. The proportion of rats infected with 

 with the disease in different localities varies greatly, as will be seen 

 in the following table : 



TABLE 1. Proportion of leper rats to the total rats examined. 



a Personal communication. 



Rats in the late stage of the disease are easily recognized by the 

 presence of a patchy alopecia associated with cutaneous and sub- 

 cutaneous nodules, which may or may not be the site of open ulcers. 

 The diagnosis can be readily confirmed by a microscopic examination 

 of a smear from an ulcer or a nodule, which will show the specific 

 bacillus of the disease in enormous numbers. 



