12 BULLETIN 248, U. S. DEPARTMENT OF AGBICULTUBE. 



As a result of international regulations, including quarantines, and 

 owing to the work of the Public Health Service, the disease has 

 not assumed serious proportions in this country. Although the mal- 

 ady has persisted for some time among rats and ground squirrels 

 in and near San Francisco, very few human cases have developed, 

 and the malady has been entirely stamped out in that vicinity. The 

 occurrence of plague in Xew Orleans during 1914 caused some excite- 

 ment, but by prompt action by the State and Federal authorities the 

 outbreak has been limited to that city and the number of human cases 

 has been small. In India, China, and a number of other countries the 

 disease is still present in epidemic form, despite the work of the 

 Indian Plague Commission and other organizations for the further- 

 ance of control work. Marked progress is being made, however, and 

 the ultimate stamping out of the pestilence may be expected. 



As has been stated, the flea is the medium by which the disease 

 is spread from rats and ground squirrels to man. These insects also 

 act as carriers from rat to rat. That the flea is responsible for the 

 transmission of plague has been determined within the last two 

 decades as a result of studies conducted by a number of investiga- 

 tors in various parts of the world. The importance of an accurate 

 knowledge of these insects in this connection is apparent to all. It 

 has been determined by the Plague Commission of India and other 

 investigators that several species of fleas may serve as vectors of 

 plague. Those which are commonly found on rats and ground squir- 

 rels and which may carry plague under certain conditions include 

 the following species : 



The Indian rat flea (Xenopsylla cheopk Both.). 



The European rat flea {Ceratophyllus fasciatus Bosc). 



The human flea {Pulex irritans L.). 



The European mouse flea {Leptopsylla musculi Duges). 



The dog flea {Ctenocephalus cams Curtis). 



The squirrel fleas {Hoplopsyllus anomalus Baker and Ceratophyl- 

 lus acutus Baker). 



The cat flea {Ctenocephalus fells Bouche). 



The rat fleas Ceratophyllus anisus Roth, and Pyglopsylla ahalae 

 Eoth. 



The former of the last two mentioned occurs in the East Indies. 

 Avhere it has been shown to be capable of carrying plague, and the 

 latter takes the place of the European rat flea in China and Japan. 

 All of these species, with the exception of the last two named, are 

 found in the United States. 



The very severe outbreak of plague in Manchuria a few years 

 ago is thought by many to have started among trappers of the 

 " tarbagan," or groundhog, as a result of having been bitten by the 

 flea. Ceratophyllus sllantlewi TTagner, which is abundant on this 

 animal. 



