TICKS — BISHOPP 395 



vaccine which has been developed by the Public Health Service. 

 Naturally the reduction of the number of ticks will decrease the 

 hazard of the disease. This matter is discussed in subsequent images 

 under ticks which serve as carriers. 



TICKS AND SPLENETIC FEVER 



One of the earliest demonstrations of the disease-transmitting role 

 of insects and related forms was that of tick transmission of sple- 

 netic fever of cattle by Drs. Theobald Smith and F. L. Kilborne, of 

 the Bureau of Animal Industry in 1893. This work has been of un- 

 told benefit to man because it pointed the way to the solution of other 

 disease problems. 



In the United States splenetic fever is carried solely by the com- 

 mon cattle tick known scientifically as BooipTi'ilus annulatus Say. 

 The disease is caused by a microscopic single-celled organism known 

 as Piroplasma bigeminnm. This organism enters and destroys the 

 red blood cells, and its multiplication is so rapid that it soon depletes 

 the blood of red corpuscles, and often causes the death of the infected 

 animal, particularly if the animal is mature. The organism is 

 passed from one generation of the tick to another through the egg. 

 This is necessary for the perpetuation of the disease because this 

 species of tick remains on the same animal from the time of its 

 attachment as a seed tick to its death as a male or its dropping as an 

 engorged female. 



Soon after the demonstration that this disease is carried by the 

 cattle tick the life cycle and habits of the vector were studied inten- 

 sively and much attention was given to ways of destroying it, both 

 on account of its seriousness as a parasite and the role it played 

 in the transmission of splenetic fever. As a result the possibility 

 of eradicating the species from a given area was conceived, and 

 finally the widespread eradication program was begun in 1906. 

 That the tick will be entirely wiped out of the United States is now 

 the belief of all progressive stockmen. "With the elimination of the 

 cattle tick splenetic fever vanishes, and improved livestock and 

 better economic conditions follow almost immediately. 



ANAPLASMOSIS OF CATTLE IN RELATION TO TICKS 



For many years the disease of cattle known as anaplasmosis was 

 confused with splenetic fever. The fact that it continued to occur 

 in cattle in areas where there were no cattle ticks helped to direct 

 attention to the fact that a malady distinct from splenetic fever 

 was present. This disease occurs sporadically in many parts of the 

 country and often takes a heavy toll among the infected herds. Its 



