STATE HYGIENE 607 



cent, of the cattle will die. Those that recover are immune, 

 and the progeny of such cattle may obtain a certain degree 

 of immunity; in this way is explained the immunity of 

 cattle on the East Coast of Africa. 



The existence of this disease in a country is a most serious 

 outlook if 95 per cent, of the cattle are to die, and yet such 

 must occur unless all movements of cattle are suspended. 

 The tick responsible for the disease exists very generally, 

 and is quite harmless until affected cattle are brought to 

 the district. It is obvious, therefore, that the entire cessa- 

 tion of cattle movements are of the utmost importance, and 

 if destruction of those in an affected area is too serious a 

 political question, then affected areas must be fenced off. 

 Such affected farms must not be stocked again with cattle 

 for some time, and the affected ticks given an opportunity 

 of feeding on insusceptible animals like sheep and goats, by 

 which means the disease will gradually disappear. 



Theiler and Stockman* have made experiments to 

 ascertain how long an infected area retains its infection 

 after the withdrawal of all cattle ; they have found that 

 fifteen months is a safe period, and believe that further 

 observation may show it to be less. They have decided one 

 vitally important point, viz., that pathogenic ticks may 

 remain active on an infected farm for at least six, and 

 perhaps eight, months after all cattle have been withdrawn. 



The removal of non-affected animals from an infected 

 district is a serious question. They would need to be 

 repeatedly dipped for safety to insure no ticks were carried 

 by them ; further, they would require to be quarantined in 

 the meantime, in case anything developed. After removal 

 to the new ground the dipping process would still have to 

 be kept up to prevent any possibility of a case arising and 

 infecting the whole district. 



On this extremely important question of dipping cattle, 

 the latest observations of Thieler and Stockmant show that 

 the application of dips in a badly infected area gives no 

 * Transvaal Agricultural Journal, No. 9, vol. iii., 1904. 

 t Op. cit. 



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