Il6 THE ANIMAL PARASITES OF MAN 



The Spirochaetes form an interesting chapter in the evolution of 

 parasites. There are free living forms, parasitic forms in the guts 

 of both vertebrates and invertebrates, and blood-inhabiting forms. 

 These probably represent the order of evolution of parasitism. The 

 blood-inhabiting forms are pathogenic to warm-blooded hosts. 



We must now consider the blood Spirochaetes and the Treponemata 

 (organisms of syphilis and of yaws). 



THE SPIROCH/ETES OF THE BLOOD. 

 There are at least two important human parasites included 

 hereunder : 

 (a) Spirochceta recurrent is (=S. obenmieri), (b) Spirochceta duttoni. 



More is known of the life-cycle of Spirochceta dnttoni, and it will 

 be convenient to consider that first. 



Spirochaeta duttoni, Novy and Knapp, 1906. 



The specific name dnttoni was also given, independently, to this parasite in 1906 

 by Breinl and Kinghorn. 



S. duttoni is the pathogenic agent of African tick fever in man, 

 prevalent in the Congo State and other parts of Africa. The full- 

 grown organism is about 16 //, to 24 //, long, and has pointed ends. It 

 is 0*25 p to o'5 //, broad. P. H. Ross and Nabarro were among the 

 earliest to see a spirochaete in the blood of patients in Uganda. It is 

 transmitted by the tick, Ornithodorus monbata. 



In the blood of the patient some of the Spirochaetes may 

 show, after staining, lighter and darker portions (chro matin dots) and 

 evidence of the possession of a very narrow membrane (fig. 54). 

 The mode of division has already been discussed. Periodicity in 

 the direction of division was first described by Fantham and Porter, 1 

 ( 1909). Just before the crisis in African tick fever, Breinl has stated 

 that S. duttoni becomes thinner in the spleen and bone-marrow 

 and rolls up into skein-like forms, which are surrounded by a thin 

 "cyst" wall (probably the periplast). Such occur in apyrexial 

 periods. Inside the cyst the spirochaete breaks up into granules. 

 Balfour and Sambon have described somewhat similar rolled up 

 forms, breaking into granules, inside the red blood cells of Sudanese 

 fowls in the case of S. granulosa (possibly only a variety of S. gal- 

 linarnm}. The intracorpuscular stage is not definitely established. 



The granule phase, however, is an essential one in the invertebrate 

 transmitter (fig. 54c). In 1905, 2 Button and Todd proved experimen- 

 tally that 0. nwubata transmitted S. dnttoni. They fed ticks, obtained 



1 Proc. Roy. Soc., B, Ixxxi, p. 500. 



2 Liverpool Sch. Trop. Med., Memoir xvii ; Lancet, Nov. 30, 1907, p. 1523. 



