12 



CIRCULAR 4 2 3, TJ. S. DEPARTMENT OE AGRICULTURE 



and stomachs, it is no wonder that rats play an extremely important 

 role in the spread and dissemination of disease. Nor do they serve 

 only as mechanical carriers of bacteria and other parasites. A num- 

 ber of their own diseases are transmissible to man and domestic 

 animals, 1 and in turn rats are subject to certain human and live- 

 stock diseases, which 

 they acquire and then 

 transmit to other 

 animal s, thus con- 

 tributing to the 

 spread and perpetu- 

 ation of the diseases. 



BUBONIC PLAGUE 



Of the rat diseases 

 transmissible to man, 

 bubonic plague is by 

 far the most impor- 

 tant. In fact it is 

 one of the most fatal 

 and most dread of all 

 diseases. In the four- 

 teenth centun\the 

 plague, or '"black 

 death" as it was 

 called, devastated 

 Europe, taking the 

 1 i v e s of 25,000,000 

 people, or a fourth of 

 the total population. 

 Since the discovery 

 that bubonic plague 

 is transmitted to 

 man by fleas from 

 rodents a n d that 

 its s p r e a d can be 

 stopped by extermi- 

 nating the rat, it is 

 not the awesome dis- 

 ease it once was, al- 

 though the death 

 rate is still tremen- 

 dous in India and 

 certain other coun- 

 tries. The present pandemic started in India in 1894 and spread to 

 all continents and to nearly every countrv of the world. During the 

 period from 1898 to 1923 there were 10^822,331 deaths from plague 

 recorded from India alone. Plague outbreaks have alarmed the 

 people of the United States on several occasions, notably those at 

 San Francisco in 1907, New Orleans in 1914. and Galveston in 1920. 

 but fortunately with the role of the rat known, the Public Health 



1 Additional details on rat-borne diseases may be obtained from the following : Hull, 



T. G. DISEASES TRANSMITTED FROM ANIMALS TO MAN. 150 pp., illUS. Springfield, 111. 



1930. 



B4337M 



Figure 9. — Under modern storage and warehouse conditions 

 rats seeking food usually have to gnaw into some type of 

 container and thus ruin far more food than they actually 

 consume. 



