FLEAS. 15 



of the dissemination of the disease among rodents by fleas, the im- 

 portance of rodent destruction and of flea control, which go hand 

 in hand, needs no further emphasis. It is not sufficient for the 

 farmer, merchant, and others concerned to depend upon the quaran- 

 tine authorities to keep plague from being introduced. They must 

 aid the quarantine officers by waging war on the rats and ground 

 squirrels and by preventing' flea breeding. 



Turning from the rat as a sanitary menace, ample argument is 

 found for its destruction on account of its importance as a destroyer 

 of various agricultural and food products. It has been conserva- 

 tively estimated that there are in the United States at least as many 

 rats as people. It has also been computed that the annual upkeep 

 of each animal amounts to between $1 and $2. From these figures 

 it is seen that the annual loss due to these rodents must be upward 

 of $100,000,000. 



The control of rats is difficult but not impossible, the principal 

 methods being trapping, poisoning, destruction by natural enemies, 

 and, probably most important of all, rat proofing. The question of 

 the relation of rats to man has been treated in publications of the 

 Public Health Service and of the Bureau of Biological Survey. 1 



This work of rodent destruction, clearing up of breeding places, 

 and rat proofing of buildings has an important beneficial influence 

 on flea conditions. Some of the hosts of the fleas are removed and 

 the breeding places of the insect destroyed to some extent. How- 

 ever, these practices can not be depended upon to control all of the 

 species of fleas important as pests. 



KALA-AZAR. 



One form of another important group of diseases of the Tropics, 

 known as kala-azar, an infectious fever, is considered by some au- 

 thorities to be carried by the dog flea and human flea. The par- 

 ticular form of the malady in question occurs in the Mediterranean 

 region. On these shores dogs and children are attacked by a similar 

 disease. Investigators have produced strong evidence that the dis- 

 ease is identical in the two hosts and that fleas are responsible for 

 its transference from the one to the other. 2 



1 Lantz, D. E. How to destroy rats. U. S. Dept. Agr., Farmers' Bui. 369, 20 p., 5 fig., 

 1909. 



2 Pleas and dogs. — In Europe with regard to infantile kala-azar, the dog has been found 

 to harbor Leishmania, and a fairly presumptive case has been made out as to the part this 

 animal plays as an intermediary host, the dog flea being the actual transmitter. Donovan 

 believes, however, that the evidence adduced so far is not in all respects convincing. The 

 occurrence of a natural flagellate of the flea has evidently not been taken into sufficient 

 account. (Donovan, Lieut. Col. C. Kala-azar, its distribution and probable modes of 

 infection. In Jour. Trop. Med. London, v. 16, no. 16, p. 253-255, 1913.) 



