896 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



taken from such recovered animals is often infective; the parasite 

 probably exists in them in a latent form through the establishment of 

 a tolerance on the part of the host. 



There is no specific treatment for babesiasis. Some of the aniline 

 drugs, used in the treatment of trypanosomiasis, such as trypan-blue, 

 are of some value. 



Many districts are kept free from red water by not allowing cattle 

 coming from infected districts to enter them. Where it exists, the dis- 

 ease is controlled by destroying the ticks on cattle with poisonous 

 washes and by occasionally plowing, or burning over, the pastures in 

 order to destroy ticks which have dropped to the ground. In the 

 United States, cattle on some farms are kept free from ticks, and conse- 

 quently from red water, by a manoeuvre which takes advantage of the 

 way in which the tick transmits the disease. The adult tick remains 

 upon her host until she is ready to deposit her eggs; she then drops off, 

 lays her eggs and dies. The young ticks, hatched from these eggs, 

 attach themselves to new hosts and it is through their bites that the 

 disease is transmitted. Therefore, since the disease is transmitted by 

 the progeny of ticks which have fed upon infected mammals, susceptible 

 cattle may be protected from the disease by preventing young ticks 

 from reaching them. This may be done by not allowing them to feed 

 over fields where ticks may have been dropped until sufficient time, 

 about ten months, has elapsed for all the ticks and their progeny to 

 have died of starvation. 



There are a number of parasites which although closely related to the 

 Babesias are usually placed in other genera. Most of these have been 

 shown to be transmitted by ticks of various species. 



EAST COAST FEVER 



Babesia parva (Theiler, 1903) 

 Syn.: Theilerla parva 



This parasite also is found in the red blood corpuscles of cattle. 

 It is the cause of a disease which is characterized by severe anaemia. 

 The intracorpuscular forms vary in form, some being slender and rod- 

 shaped, the others being more rounded or pear-shaped. They may be 

 arranged to form a cross, and this is not due to segmentation but to 

 fortuitous grouping in heavily infected cells. They are regarded as 



