INSECTS INJURIOUS TO CATTLE 415 



Since the ticks cannot survive the cold of northern 

 winters it v^'ill be apparent that the pastures north of 

 a certain Hne cannot be permanently infected with what 

 may be called the disease germs of Texas fever. On 

 the other hand^ where the winter climate is sufficiently 

 mild, areas exist in which, as managed in the past, the 

 ticks are always more or less present. It will also be 

 apparent that this dividing line will be to some extent 

 a shifting one, varying more or less with the character 

 of the winters. The United States Department of Agri- 

 culture has recognized this fact when establishing the 

 so-called quarantine line south and east from which 

 cattle may not be shipped north and west except for 

 immediate slaughter, unless properly dipped according 

 to government regulations, between the dates of Febru- 

 ary 15 and December i. In a general way, the quaran- 

 tine line may be said to run from the Atlantic westward 

 through central Virginia and Tennessee. It then de- 

 flects southward somewhat east of the central portions 

 of Indian territory and Texas. It also includes lower 

 California. As early as 1814, the people of Virginia had 

 taken measures to prevent cattle in certain areas farther 

 south from being brought into the state. Protective 

 measures sought at sundry times in various states cul- 

 minated in the establishment for the whole country of 

 protective measures governing the movement of cattle 

 from infected areas. 



Texas fever occurs in the acute and chronic forms. 

 In the latter form it may be in the nature of a relapse, 

 which usually occurs in the autumn, and is so mild that 

 but for the emaciation which follows its presence would 

 scarcely be recognized. In the acute form, the tem- 

 perature is always high, in some instances as high as 

 108°, and it usually remains high from five to seven days, 

 within which period many of the animals die. Should 

 it drop suddenly to sub-normal, the danger is imminent 

 that collapse may follow. The affected animals usually 



