158 



MALCOLM EVAN MACGREGOR. 



Notes to Table II. — Diseases of Bacterial Origin. 



In the majority of cases, diseases of this class have an indirect transmission by insects, 

 that is to say, instead of the organism entering the body of the host through inoculation 

 by the bite of an insect (direct transmission), the organisms are carried in or on the 

 insect's body, and are deposited by contact on human food or skin abrasions, and in 

 this manner cause infection. 



Bacillus tuberculosis may be disseminated by house-flies feeding on infective sputum, 

 as was first shown by Spillman and Haushalter (1887) and subsequently by the in- 

 vestigations of other workers. With the high vitality and resistance to drying 

 possessed by B. tuberculosis, the possibly long incubation period within the body, and 

 the insidious onset of the disease, the danger from Musca domestica in this connection 

 is still not sufficiently recognised. 



Exceptions to the rule of indirect transmission are plague, transmitted by the bite 

 of certain fleas, and typhus that has direct transmission through the bite of lice. 

 Direct transmission by insects of bacterial diseases may possibly also occur in certain 

 instances in the spread of tuberculosis and leprosy. 



Tf Wolbach's organism (see Table I. and notes thereto) is proved to be the cause of 

 Eocky Mountain spotted fever, this will also be a disease of bacterial origin with 

 direct transmission through a tick, Dermacentor venustus. 



Table II. 

 The more Important Insect-borne Diseases of Bacterial Origin. 



(The word "Flies" in these tables includes: — Musca domestica , Fannia spp., 

 Calliphora spp., Lucilia spp., and Sarcophaga spp.) 



Organism. 



Host. 



Disease. 



Vector. 



Bacillus anthracis 



Man and 

 animals. 



Anthrax 



* Flies, Tabanidae (f), 

 beetles (?). 



„ dysenteriae 



Man 



Bacillary dysentery 



Flies {Musca domestica, 

 Calliphora spp., Lucilia 

 spp.).* 



„ leprae 



Man 



Leprosy 



Flies (?), fleas (?), bedbugs 

 (!), skin mites (?), mos- 

 quitoes (?). 



„ paratyphosus A. . 



Man 



Paratyphoid fever 



Flies.* 



„ paratyphosus B. . 



Man 



?> 55 



Flies.* 



„ pestis 



Man and 

 rats. 



Plague 



Fleas. * 



„ tuberculosis 



Man and 

 animals. 



Tuberculosis 



Flies, cockroaches, fleas ( I), 

 bed-bugs (?). 



Rickettsia prowazeki, typhi- \ 

 exanthematici . . . . 1 

 Plotz's organism . . . . J 



Man 



Typhus fever 



Lice. * 



Bacillus typhosus 



Man 



Typhoid fever 



Flies.* 



