CHAPTER X 
ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA 
[Continued] 
Arthropods and Spiroch.etoses of Man and Animals 
The term spiroehaetoses is applied to diseases of man or animals 
which are due to protistan parasites belonging to the group of slender, 
spiral organisms known as spirochaetes. 
There has been much discussion concerning the relationship of 
the spirochaetes. Formerly, they were regarded as bacteria closely 
related to the forms grouped in the genus Spirillum. The results 
of the detailed study which the spirochaetes have received in 
recent years, have led most of the workers to consider them as belong¬ 
ing to the protozoa. The merits of the discussion we are not con¬ 
cerned with here, but rather with the fact that a number of diseases 
caused by spirochaetes are arthropod-borne. The better known of 
these we shall discuss. 
African Relapsing Fever of Man —It has long been known to the 
natives of Africa and to travelers in that country, that the bite of a 
certain tick, Ornithodoros moubata, may be followed by severe or 
even fatal fever of the relapsing type. Until recent years, it was 
supposed that the effect was due to some special virulence of the tick, 
just as nagana of cattle was attributed to the direct effect of the bite 
of the tsetse-flv. The disease is commonly known as “tick-fever” 
or by the various native names of the tick. 
In 1904, Ross and Milne, in Uganda, and Dutton and Todd on the 
Congo, discovered that the cause of the disease is a spirochsete which 
is transmitted by the tick. This organism has been designated by 
Novy and Knapp as Spiroclueta duttoni. 
Ornithodoros moubata (fig. 142), the carrier of African relapsing 
fever, or “tick-fever,” is widely distributed in tropical Africa, and 
occurs in great numbers in the huts of natives, in the dust, cracks 
and crevices of the dirt floors, or the walls. It feeds voraciously 
on man as well as upon birds and mammals. Like others of the 
Argasidce, it resembles the bed-bug in its habit of feeding primarily 
at night. Dutton and Todd observed that the larval stage is under¬ 
gone in the egg and that the first free stage is that of the octopod 
nymph. 
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