THE TICK GROUP OF RELAPSING FEVERS 



919 



II. The Tick Group, which is characterized by being spread by 

 the genus Ornithodorus. The known forms are the African (perhaps 

 a separate East African), the Persian, the Colombian, with the 

 Panamanian. 



This group differs from the louse group in the pre-eminence of 

 the infective gramde, which, according to many authorities, is in 

 itself doubtful. 



Spirochsetes enter the tick with the infective feed, bore their way 

 into the cells of various organs, and break up into coccoid bodies, 

 the infective granules. These granules pass into the second genera- 

 tion, and so the tick is a preservative reservoir. They also pass into 

 the Malpighian tubules, from which they escape when the 

 thick white Malpighian excrement is passed, which only takes 

 place towards the end of a feed. The spirochsetes now enter 

 the new host via the hole made in the skin by the tick for its 

 meal of blood. 



II. The Tick Group of Relapsing Fevers. 



Parasite. 



Preservative 

 Host. 



Preserva- 

 tive 

 Reservoir. 



Infection. 



Inter- 

 mediate 

 Host. 



Trans- 

 mission. 



Forms allied to 

 5. duttoni and 

 found in Afri- 

 ca, East Afri- 

 ca, Colombia, 

 Panama, and 

 perhaps in 

 Persia . 



Species of 

 Ornithodorus — 

 e.g., 0. moubata, 

 0. turicata, 

 0: talagcs, 

 and perhaps 

 0. savignyi. 



The ticks 

 by 



hereditary 

 trans- 

 mission. 



The 

 infective 

 granules(?). 



Contami- 

 native. 



Man. 



Blood 

 spiro- 

 chaetes. 



Ingestive. 



We have followed Balfour's suggestion that the Persian relapsing 

 fever is not caused by Argas persicus, but by a species of Ornitho- 

 dorus, probably 0. savignyi. It must be admitted that many 

 authorities disbelieve in the infective granule. 



4. PHLEBOTOMUS FLIES. 



Verruga Peruviana. — It has been suggested that the carrier of this 

 disease may be Phlebotomus verrucarum Townsend, 1913, but this 

 appears to be very doubtful. 



