222 Arthropods as Essential Hosts of Pathogenic Protozoa 
The term babesiosis is applied to a disease of man or animals 
which is caused by minute protozoan parasites of the genus Babesia, 
living in the red blood corpuscles. These parasites have usually been 
given the generic name Piroplasma and hence the type of disease 
which they cause is often referred to as “ piroplasmosis.” The best 
known illustration is the disease known in this country as Texas 
fever of cattle. 
Cattle Ticks and Texas Fever— The cattle disease, which in the 
United States is known as Texas fever, is a widely distributed, exceed¬ 
ingly acute disease. In Australia it is known as redwater fever and 
in Europe as haemoglobinuria, due to the fact that the urine of the 
diseased animals is discolored by the breaking down of the red blood 
corpuscles infested by the parasite. 
In their historical discussion, Smith and Kilbourne, point out that 
as far back as 1796 it was noted that Southern cattle, in a state of 
apparent health, might spread a fatal disease among Northern herds. 
As observations accumulated, it was learned that this infection was 
carried only during the warm season of the year and in the depth of 
winter Southern cattle were harmless. Moreover, Southern cattle 
after remaining for a short time in the North lost their power to 
transmit the disease, and the same was true of cattle which had been 
driven for a considerable distance. 
Very significant was the fact that the infection was not com¬ 
municated directly from the Southern to Northern cattle but that 
the ground over which the former passed was infected by them, and 
that the infection was transmitted thence to susceptible cattle after 
a period of not less than thirty days had elapsed. 
Of course a disease as striking as this, and which caused such 
enormous losses of cattle in the region invaded was fruitful in theories 
concerning its causation. The most widespread was the belief that 
pastures were infected by the saliva, urine, or manure of Southern 
cattle. There were not wanting keen observers who suggested that 
the disease was caused by ticks, but little weight was given to their 
view. 
Various workers had described bacteria which they had isolated 
from the organs of the diseased animals, but their findings could not 
be verified. In 1889, Smith and Kilbourne discovered a minute, 
pear-shaped organism (fig. 138) in the red blood corpuscles of a cow 
which had succumbed to Texas fever. On account of their shape 
