360 TICKS 



Ornithodorus moubata (Fig. 155). A year later Dr. Ricketts 

 showed that spotted fever in the United Stated was dependent 

 upon a tick, Dermacentor venustus, for its transmission. It is 

 now known that ticks serve as intermediate hosts for a consider- 

 able number of disease germs of two different groups, the spiro- 

 chetes and the Piroplasmata. The various forms of relapsing 

 fever of man are caused by spirochaetes, and it is possible that 

 all the different types of this disease may be transmitted by 

 ticks, though in some of the types other arthropods act as the 

 usual transmitters. Many diseases of domestic animals are 

 caused by organisms of the group Piroplasmata (see p. 182), 

 including Texas fever of cattle in North America, East Coast 

 fever of cattle in Africa, biliary fever of horses in Asia and Africa, 

 and similar diseases of sheep, dogs, rats and monkeys. The only 

 human disease positively known to be caused by an organism 

 of this group is Oroya fever of Peru, caused by Bartonella bacilli- 

 formis (see p. 178). Whether or not a tick is instrumental in 

 transmitting this disease is not yet known. Rocky Mountain 

 spotted fever was at one time thought to be caused by a member 

 of the Piroplasmata, but the parasite of this disease is still un- 

 known. The fact that it is transmitted by a tick suggests that 

 it may be found to belong either to the spirochaetes or to the 

 Piroplasmata. Ticks have also been suspected of carrying the 

 East Indian form of kedani fever which in Japan is transmitted 

 by a larval mite, but this has not been proved. 



Ticks and Relapsing Fever. — The fact that tick bites frequently 

 give, rise to serious fever and illness, now known as relapsing 

 fever, which not infrequently result in death, has been well known 

 in Africa for many years, in fact Livingston in his " Darkest 

 Africa " speaks of this disease as resulting from tick bites. The 

 implicated ticks, Ornithodorus moubata, known as " tampans " or 

 " carapatos," are very common pests in shaded places in the 

 dirty thatched houses of the natives, and are difficult to avoid. 

 They occur chiefly along the routes of travel, being readily 

 carried and dispersed by caravans. They live also in the bur- 

 rows of warthogs. A detailed account of the role played by 

 the tick in harboring and transmitting relapsing fever spiro- 

 chaetes and a description of the disease can be found in Chap. 

 IV, p. 42. 



The tampan is a broad oval tick (Fig. 155), mud-colored, 



