THE FLEA AND ITS RELATION TO PLAGUE. 



By Passed Assistant Surgeon CARROLL Fox, 

 United States Public Health and Marine-Hospital Service. 





THEORIES AS TO TRANSMISSION OF PLAGUE. 



1. Direct contagion from man to man. 



2. Through slight abrasions of the skin, mucous membranes of 

 mouth, tonsils, nose, and conjunctiva receiving contaminated material. 



3. Through the respiratory tract, from air contaminated with 

 dried infectious sputum or dejecta. (Possibly the cause of primary 

 pneumonic plague.) 



4. Through the alimentary tract from food contaminated with 

 saliva or excretions from plague patients, or dejecta or the feet of 

 insects that have fed on plague material. In the case of rats, from 

 eating the carcasses of infected rats. 



5. Infected clothes, soil, or houses. 



6. Through the bites of insects, especially the flea. 



It has been noticed for many years that an epidemic of plague in 

 man was associated with an epizootic of high mortality among rats, 

 but it was not until Yersin discovered the Bacillus pestis in 1894 that 

 the disease in man and rats was shown to be identical. The first 

 five theories are not satisfactory in explaining the epidemiology of 

 plague, and in 1897 Simond advanced the theory that plague was 

 carried by means of fleas. Hankin in 1898 also suggested an insect 

 as an intermediate host. This theory has been developed by Ash- 

 burton Thompson, Gauthier and Raybaud, Liston, Verjbitski, and 

 others, and finally by the last Indian Plague Commission, whose 

 work makes a distinct advance in our knowledge of this subject. 

 The reader is referred to the work of this commission for a review 

 of the subject, which has been liberally used in the preparation of 

 this paper. 



a Journal of Hygiene (Vol. VI, No. 4; Vol. VII, No. 3; Vol. VII, No. 6; Vol. VIII, 



No. 2). 



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