DISEASES CARRIED BY FLEAS 351 



mice, are proven hosts of plague. The following fleas have been proven 

 to be carriers of the organism: Xenopsylla cheopis Rothschild, Cerato- 

 phyllus fasciatus (Bosc) Curtis, C. acutus Baker, C. silantiewi Wagner, 

 Pulex irritans Linnaeus, Ctenocephalus canis (Curtis) Baker, Lep- 

 topsylla musculi Duges and Pygiopsylla ahalae Rothschild. 



The first successful record of transmission of plague by fleas was 

 made by Simond in 1898, and corroboration was first obtained by Verjbit- 

 ski in 1903 and Liston in 190-t. 



iNIany other workers have since then proven the role of the flea in 

 carrying this disease. A synopsis of the evidence is presented by Herms 

 in his textbook. The flea takes up the organism with the blood of the 

 host. The stomach of the rat flea, Xenopsylla cheopis, is capable of 

 receiving as many as 5000 germs while imbibing the blood from a plague 

 rat. Both males and females may carry the infection and they may 

 remain infective during an epidemic for 20 days. The Indian Plague 

 Commission found the bacilli only in the stomach and rectum of the 

 fleas and never in the salivary glands or body cavity and rarely in the 

 esophagus. They conclude that the normal course of the bacilli is to be 

 voided in the feces and to be inoculated by scratching in of the feces. 

 Bacot and Martin, however, have come to the conclusion that plague can 

 be transmitted during the act of biting when a temporary blocking or 

 obstruction of the proventriculus takes place, causing bacillus-laden blood 

 to be forced back or regurgitated into the wound, thus producing infec- 

 tion. 



Bacterium tularense McCoy and Chapin, cause of a fatal RODENT 

 PLAGUE which affects the California ground squirrel, Citellus beecheyi, 

 may also be transmitted by fleas. McCoy and Chapin placed fleas 

 (Ceratophyllus acutus Baker and C. fasciatus Bosc) with an inoculated 

 guinea pig and allowed them to remain there until the animal died. They 

 were then collected, and crushed and inoculated into healtliy guinea pigs. 

 The four animals inoculated with crushed C. fasciatus immediately after 

 the fleas were removed from the dead guinea pig, died of the disease ; two 

 of four inoculated after 24- hours, died; and one out of four inoculated 

 after 48 hours, died. Two out of four animals inoculated with crushed 

 C. aciltus immediately after removal from the dead guinea pigs, died, but 

 none died that were inoculated on subsequent days, although some devel- 

 oped an apparently chronic form of tlie disease. They also succeeded in 

 obtaining one actual case of transmission. About 100 fleas collected from 

 an animal dead of tlie disease were placed in a clean cage with a healthy 

 ground squirrel. It died 15 days later and presented the usual lesions 

 of the plague-like disease, the bubo being in the neck. 



