Cattle Ticks and Texas Fever 
225 
These results have been fully confirmed by workers in different 
parts of the world,—notably by Koch, in Africa, and by Pound, in 
Australia. 
The disease is apparently transmitted by Boopliilus annulatus 
alone, in the United States, but it, or an almost identical disease, 
is conveyed by Ixodes hexagonus in Norway, Ixodes ricinus in Finland 
and France and by the three species, Boophilus decoloratus , Hyalomma 
cegypticum (fig. 140 and 141), and Hcemaphysalis punctata in Africa. 
In spite of the detailed study which it has received, the life cycle 
of Babesia bovis has not been satisfactorily worked out. The asexual 
reproduction in the 
blood of the vertebrate 
host has been described 
but the cycle in the tick 
is practically unknown. 
More successful 
attempts have been 
made to work out the life 
cycle of a related species, 
Babesia canis, which 
causes malignant jaun¬ 
dice in dogs in Africa 
and parts of Southern 
Europe. In this in¬ 
stance, also, the disease 
is transmitted by heredity to the ticks of the second generation. 
Yet the larval, or “seed ticks,’’ from an infected female are not 
capable of conveying the disease, but only the nymphs and adults. 
Still more complicated is the condition in the case of Babesia ovis of 
sheep, which Motas has shown can be conveyed solely by the adult, 
sexually mature ticks of the second generation. 
In Babesis canis , Christopher (1907) observed developmental 
stages in the tick. He found in the stomach of adult ticks, large 
motile club-shaped bodies which he considered as ookinetes. These 
bodies pass to the ovaries of the tick and enter the eggs where they 
become globular in form and probably represent an oocyst. This 
breaks up into a number of sporoblasts which enter the tissues of 
the developing tick and give rise to numerous sporozoites, which 
collect in the salivary glands and thence are transferred to the 
vertebrate host. A number of other species of Babesia are known 
141. 
Hyalomma aegypticum. Capitulum of female; 
(a) dorsal, (6) ventral aspect. 
