GEOGRAPHICAL DISTRIBUTION 



351 



carefully investigated at that time but nothing beyond a very 

 accurate description of the gross lesions was obtained. Later, 

 Salmon determined the boundary line between the non-infected 

 and the permanently infected districts, or what is now known 

 as the Texas fever line. (See Plate IIJ. In 1889, the Bureau 

 of Animal Industry undertook a systematic investigation into 

 the nature of this disease, which resulted in the same year in 

 the discovery of its specific cause by Dr. Theobald Smith and 

 later the demonstration of the fact that the disease is trans- 

 mitted from southern to northern cattle through the medium 

 of the cattle tick. Prior to this (1888), v. Babes had found 

 an intraglobular parasite in the blood of cattle suffering from 

 an epizootic disease (hemoglobinuria) in Roumania. While 

 at first these diseases were thought to be different in their 

 etiology they are now believed to be identical. 



A number of investigations have been made by the Bureau 

 of Animal Industry, the State Experiment Station and State 

 Board of Agriculture of Missouri and Texas, the L,ouisiana 

 Experiment Station and by the Queensland Government, 

 Australia, for the purpose of obtaining a practical method for 

 the production of immunity against Texas fever in susceptible 

 cattle. The results that are being obtained are promising, as 

 they have made it possible to take northern cattle into the 

 infected territory of the south. 



§ 266. Geographical distribution. In the United States 

 the distribution of Texas Fever corresponds with that of the 

 cattle tick (^Boophilus annulatus). This includes, with pos- 

 sibly a few small exceptional areas, that portion of the country 

 south of the "Texas fever line" which is shown by a red line 

 on the accompanying map but which is changing constantly 

 by virtue of the spread or elimination of the tick. It has been 

 identified with the tick fever of Australia which has become 

 a source of great loss to the cattle industry of that country. 

 I^igni&res has identified the disease in South America (Argen- 

 tine Republic). It is also reported to be identical with a 

 malady affecting cattle along the Danube river, in the Balkan 



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