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 



