504 Relapsing Fever 



subequal, more pointed and about equidistant, while those of savignyi are 

 unequal, less pointed and not equidistant. The tarsus of leg IV in moubata is 

 shorter and thicker than in savignyi, and its humps are nearly equidistant. 

 Eyes absent. Length 8-12 mm.; breadth 6-10 mm. The eggs are ovoid, meas- 

 ure 0.8-0.9 mm. in length, are smooth on the surface and dark yellow in color. 



Habitat. Africa: from British East Africa to the Transvaal, and across to the 

 Congo; southward to German East Africa and Cape Colony. It is common in 

 Egypt, Abyssinia and in parts of Somaliland and in Portuguese East Africa. 



Ornithodorus savignyi is chiefly a parasite of the camel and only occasionally 

 bites man; Ornithodorus moubata is essentially a human pest. 



The eggs of these ticks hatch in eight to fourteen days. The larval stage which 

 has sixlegsis spent in the eggs and the creature that emerges is usually a first nym- 

 phalinston, which has eight legs. After hatching it remains inactive for several 

 days, then becomes very active and ready to suck blood. As it grows it becomes 

 voracious, distending itself with blood, then dropping off, hiding itself for a time, 



I 



Male Female 



Fig. 205. Pediculus pubis, Phthirius inguinalis or crab-louse. X 17. (From 

 Beattie and Dickson's "A Text-book of General Pathology," by kind permission 

 of William Heinemann, Publisher.) 



molting, then being ready to feed again. This continues for a number of 

 months, the ticks molting four times before passing from the nymph to the adult 

 stage. ^ 



Ornithodorus moubata is a common inhabitant of the native African huts along 

 the caravan routes. To avoid it and escape relapsing fever R. Koch in his 

 African expedition camped near but not in the villages, and avoided the native 

 houses. It lives in the cracks in the mud walls, in the thatch, in the mats and 

 sometimes simply upon the ground where its small size and dull color make it 

 difficult to see. From these hiding places it crawls at night and like abed-bug 

 attacks the sleeping host. When handled it feigns death, remaining quiet for 

 so long a time that it is hard to believe it alive. 



The Ornithodorus savignyi is less adapted to the requirements of the spiro- 

 chseta than its relative. Brumpt* found that the spirochaeta did not pass 

 through the eggs of O. savigyni to subsequent generations, and that the in- 

 fectivity of the tick itself soon was lost. The spirochaetae remain indefinitely 

 in O. moubata, and are passed through their eggs to at least three generations. 

 It is, therefore, difficult to be certain that any particular tick is uninfected unless 

 its progenitors be known. 



The spirochaeta pass from female to the ovum and infect the young nymphs as 

 such. The granules observed in the eggs of infected ticks, also occur in those of 

 non-infected ticks and have nothing to do with the spirochaeta. 



*" Precis de Parasitologie," 1910, 538. 



