Arthropods and Disease Transmission 355 



and in other parts of the southwest Pacific this same disease goes 

 under the name of scrub typhus, tropical typhus, and mite-home 

 typhus. Rodents serve as the principal reservoir of these mites. 



LICE 



Man is affected by two species of lice, namely, the crab louse 

 (Phthirus pubis) and the head and body louse (Pedicuhis hii- 

 77ianus). The crab louse, which localizes chiefly in the hairs of the 

 pubic region, does not transmit disease. Head and body lice may 

 be instrumental in spreading typhus, trench fever, and at least 

 one form of relapsing fever. Rickettsia prowazeki is the cause 

 of European or epidemic typhus. When the skin has been pene- 

 trated by the louse, infection of the person may be caused by a 

 deposition of louse feces on the site, and the natural tendency to 

 scratch the itching area will drive the contaminated feces into the 

 skin opening. Crushing the lice may also cause infection, and 

 there is some evidence that the bite of the louse in itself might be 

 sufficient to result in typhus. 



Trench fever is probably of rickettsiaL etiology, and relapsing 

 fever is caused by the spirochete Borrelia recurrentis transmitted 

 by lice when they are crushed on the skin. 



In general, bacterial diseases are mechanically transmitted by 

 arthropods, while virus and rickettsial diseases are biologically 

 transmitted. That is, the viruses and rickettsiae must live' within 

 the arthropod host part of the time. 



There are many arthropods which are vectors, or potential vec- 

 tors, of disease, but a complete discussion of their activity is not 

 warranted here. The more important vectors and the more serious 

 diseases have been mentioned. 



PREVENTION OF THE SPREAD OF 

 ARTHROPOD-BORNE DISEASES 



Diseases transmitted by arthropods cause more human misery 

 from the standpoint of numbers of cases than is generally realized. 

 Prevention of these diseases is aimed primarily at destroying the 

 breeding grounds of the vectors or breaking a link in the chain of 



