CHAPTER XXIV 



Diseases Carried by Fleas ^ 

 W. Dwight Pierce 



Fleas pass their immature stages in filth outdoors and indoors. The 

 larvae breed in dirt and are usually to be found where animals are com- 

 mon, but they may breed in the dirt of kennels and stables, in the open 

 country, in carpets, and closets of houses and especially in cellars. They 

 are always to be found where rats or mice are common. 



Because of the fact that the larva imbibes filth and the adult sucks 

 blood, we should seek other possibilities of disease transmission which 

 have not hitherto been investigated. Past investigations with fleas 

 have dealt principally with the possibility of conveying disease by the 

 bite of the adult flea. The work which has been done on flies and which 

 was quoted in a preceding lecture showed that larva could take up bac- 

 teria and that these would persist into the adult stage. It is therefore 

 essential in the future investigations of disease transmission by fleas that 

 account be taken of the possibility of the flea larvse taking up the organ- 

 ism from the filth in which they breed and retaining these organisms 

 to be transmitted by the adult. That they may do this is demonstrated 

 in the case of the tape worms mentioned below. 



Fleas do carry disease, that we know. But probably they can carry 

 diseases which they have never been credited with. There lies our field 

 of investigation. 



The arrangement of organisms transmitted by fleas follows that 

 adopted for previous lectures. 



PLANT ORGANISMS TBANSMITTED BY FLEAS 



Thallophyta: Fungi: Schizomycetes: Bacteriacece 



Bacillus pestis Kitasato, the cause of BUBONIC PLAGUE of man 

 and rodents, is carried by fleas. Nine species of rodents, mainly rats and 



'This lecture was presented on October 38, 1918. It is considerably modified for 

 the present edition. 



350 



