i6o 



Pasteur ella pest 1 s (Lehmann and Neumann) 

 Bergey et al. 



Insects concerned: Plague bacilli have "been cited as 

 associated with an extensive number of arthropods. The 

 species listed below are perhaps the most important and 

 representative ones from the standpoint of plague trans- 

 mission. 



Fleas : Xenopsylla cheopis ; Xenopsylla astia; Xenopsylla 

 "brasiliensis ; Diamanus montanus ( Ceratophyllus acutus ) ; 

 Nosopsyllus fasciatus ( Ceratophyllus fasciatus ) ; Monopsyllus 

 anisus ( Ceratophyllus anisus ); Oropsylla silantiewi ; 

 Ceratophyllus tes quorum ; Dinopsyllus lypusus ; Leptcpsylla 

 musculi; Ctenophthalmus agyrtes ; Pulex irritans; Cteno - 

 phthalmus agyrtes ; Pulex irritans; Ctenocephalides canis; 

 Ctenocephalides fells ; Ceratophyllus gallinae . 



The reader is referred to the work of Eskey and Haas 

 (19^0) for a list of , other species of fleas which are 

 potential vectors of plague, especially among rodents. 



Lice: Haematopinus columbianus ; Linognathoides citelli . 

 The implications against many of the following have 

 "been mainly of an incidental nature and are concerned 

 largely with experimental findings : 



Ticks: Ixodes autumnalis ; Rhipicephalus schulzei ; 

 Argas persicus ; Hyalomma volgense ; Derma centor silvarum . 

 Flies: Musca domestica ; Stomoxys calci trans . 

 Beetles: Necrophorus dauricus and others. 

 Mosquitoes : Culex pipiens , A&des aegypti . 

 Ants, roaches, and mites have also "been suspected of 

 carrying plague "bacilli. 



The plague "bacillus was discovered in 189^ independently 

 by Kitasato and by Yersin. 



Three years later Ogata (1897) and soon thereafter 

 Simond (1898) pointed out, on epidemiologic and experimen- 

 tal ground, the role of the flea in the transmission of 

 plague bacilli. However, it was the English Plague Re- 

 search Commission that clarified and established the essen- 

 tial part that fleas play in the spread of plague, especially 

 among rodents. 



Although the number of fleas known to transmit the 

 plague "bacillus is large and ever -increasing, the principal 

 vector is the rat-flea Xenopsylla cheopis . It is present 

 on wild rats in many parts of the world and is the pre- 

 dominant species in India, Java, Egypt, and most parts of 

 China. Besides its widespread occurrence, there are 

 other factors which make this species an efficient vector. 

 As stated by Eskey (1938); "When compared with all other 



