FLEAS AS PESTS TO MAN AND ANIMALS. 9 
FLEAS IN RELATION TO BUBONIC PLAGUE. 
During recent years bubonic plague has been introduced into the 
United States on both the Pacific and Gulf coasts. The infestation 
in California persisted for a number of years, although it was closely 
held in check through the efforts of the Public Health Service and 
the State board of health. The disease around San Francisco not 
only persisted among the rats, but gained a foothold among ground 
_squirrels in the counties adjacent to San Francisco Bay. A strenuous 
fight is being waged against rats in all of the Pacific ports and against 
ground squirrels in the territory where the disease has become estab- 
lished among these rodents. 
During the year 1914 the disease broke out in New Orleans, but 
strict quarantine measures and an energetic campaign against the 
rats kept the malady from spreading and limited the number of 
human cases. 
While the plague situation is now well in hand it is important 
that all have a general knowledge of the essential steps in controlling 
the disease. The prevention of the introduction of bubonic plague 
depends to a considerable extent upon quarantine regulations at our 
ports of entry, but it is of even greater importance that united effort 
be put forth to control the rats in the seaport towns. The work 
should not stop here, as it is of importance that concerted action be 
taken against rats and ground squirrels throughout the entire country. 
It may be gathered from what has been said that the control of 
bubonic plague depends almost entirely upon the destruction of the 
rat population. This is essential in that the disease always starts by 
gaining a foothold among the rats, and as these animals die and the 
fleas leave them and attack man the human cases of plague begin. 
In addition to the importance of rat control from the standpoint 
of disease prevention there is every reason to wage war against these 
pests on account of their importance as destroyers of agricultural and 
other products. It has been estimated that the loss in the United 
States due to rats exceeds $100,000,000 annually. The principal 
methods of combating these rodents* are rat proofing, trapping, 
poisoning, and destruction by natural enemies. 
With the reduction in numbers of rats and mice the various species 
of fleas which infest them and which in turn may play a part in 
carrying bubonic plague are greatly reduced in numbers. The clean- 
ing up of the breeding places of rats and the destruction of their 
nests will also accomplish the extermination of a large number of 
fleas in the immature stages. Some of the methods of trapping fleas 
mentioned under “ Means of Repression ” will aid in destroying those 
1 The methods of rat control are discussed in Farmers’ Bulletin 369, U. S. Department 
of Agriculture, by Mr. D. E. Lantz, of the Bureau of Biological Survey. 
