BACTERIAL DISEASES OF THE RAT, OTHER THAN 

 PLAGUE AND RAT LEPROSY. 



By Donald H. Cureie, 

 Passed Assistant Surgeon, United States Public Health and Marine-Hospital Service. 



So far as is known, the several species of rats that are found about 

 the habitations of man — Mus norvegicus, Mus rattus, Mus alexan- 

 drinus, and Mus musculus — are naturally subject to but few bac- 

 terial diseases as compared to some other animals. Interest in this 

 matter has only recently been aroused, owing to the r6le played by 

 the rat in the spread of bubonic plague. When we consider the 

 immense number of rats that have been examined in connection with 

 antiplague work by trained investigators in recent years, and that 

 to many investigators the thought must have come that the discovery 

 of some rat destroying bacterium would be of the greatest utility, it 

 appears more than probable that few such natural diseases exist. 



Plague is the one natural bacterial disease that has demonstrated 

 its power to destroy these rodents in numbers sufficiently large to 

 attract general attention; scientific investigation has only been able 

 to add a few other bacterial diseases, and these are probably for the 

 most part rare ones, causing the death of a very small percentage of 

 the total rat population. 



Of the "natural" diseases (i. e., spontaneous, in distinction to dis- 

 eases that can only be produced artificially, under laboratory condi- 

 tions) the following are the more important ones : 



Rat plague and rat leprosy, which are made the subject of special 

 chapters in this publication, must be mentioned as the most impor- 

 tant diseases observed among rat populations. 



DANYSZ'S BACILLUS OR BACILLUS TYPHI MURIUM OF LOEFFLER. 



These are probably identical organisms, differing only in their 

 degree of virulence, at least their pathogenicity alone distinguishes 

 them in the laboratory. They are both members of the paracolon 

 group. They produce a diffuse cloudiness in broth, ferment glucose 

 but not lactose or saccharose, do not liquefy gelatin nor coagulate milk, 



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