674 A MANUAL OF BACTERIOLOGY 



is a short rod in pairs, joined end to end ; many exhibit 

 bipolar staining, and they occur in large numbers, par- 

 ticularly in the endothelial layer of the vessels. All 

 attempts at cultivation have so far failed. For a bac- 

 terium, the organism is peculiar in that the best staining 

 method is by means of Giemsa stain applied after Zenker 

 fixation. The disease is communicable to the monkey 

 and guinea-pig, and an animal immunised against the 

 disease is still susceptible to infection with typhus fever, 

 so that it would seem to be distinct from the latter. 

 Rocky Mountain spotted fever is conveyed by a tick 

 (Dermacentor venustus), in which the same parasite is 

 found, and the ground squirrel or, possibly, the goat, 

 may be a reservoir of the parasite. As mentioned above, 

 Rickettsia bodies are also met with in this disease. 



Dengue 



No organism, bacterium or protozoon, has been demon- 

 strated in this disease. The intra-venous inoculation of 

 filtered dengue blood into healthy individuals is followed 

 by an attack ; the organism is therefore probably ultra - 

 microscopic. The disease can be transmitted by a mos- 

 quito, Stegomyia fasciata, and possibly by Culex fatigans, 

 and this is probably the common mode of infection. 1 



Phlebotomus Fever 



A fever of short duration (three days) occurs in South 

 Austria, the malady being somewhat like dengue. It is 

 known locally as " pappataci," and an apparently iden- 

 tical disease has been described by Birt 2 in Malta under 

 the name of " phlebotomus fever." Investigation has 

 shown that this disease is conveyed by the bite of a dip- 



1 See Cleland, Journ. of Hygiene, vol. xviii, 1919, p. 217. 



2 Journ. Roy. Army Med, Corps, August, 1910. 



