608 VETEKINAEY HYGIENE 



guarantee against the further spread of the disease, and no 

 hope for extinguishing an outbreak unless the animals are 

 also removed to a fresh pasture, which, as we have mentioned, 

 is a serious risk to run. It is true that systematic dipping, 

 as mentioned p. 422, will reduce the number of ticks on a 

 farm, but it is principally those varieties of ticks which 

 remain on the animal for several days which are thus 

 exterminated. The life history of the brown tick shows 

 that the intermediate stages drop off in three days, and it 

 would be impossible to catch these by any periodical dipping 

 possible, especially when poisonous dips like arsenic, or 

 irritating ones like paraffin, are used. 



Public dipping tanks have proved themselves in this 

 disease to be a source of infection, healthy cattle becoming 

 affected with the ticks dropped by diseased cattle. 



In a European country the entire destruction of the 

 affected herd would be necessary, with restriction against 

 stocking with cattle for many months. Koch proposes to 

 immunise animals by the repeated injection of the blood of a 

 recovered case at intervals of fourteen days. The process 

 is a long one, and takes four or five months before 

 immunity is said to be established. Gray in Ehodesia found 

 it to be useless. 



Theiler and Stockman are of opinion that to trust to 

 dipping alone to keep off East Coast Fever is useless. If a 

 farm be non-affected in an affected district, the only way to 

 maintain it in this condition is to fence it, never allow the 

 cattle to go off it, nor permit fresh cattle to enter until they 

 have undergone a six weeks' period of quarantine. 



Equine malaria, or Bilious fever in horses, is another 

 disease due to a pyroplasma, and is presumably tick infected ; 

 the disease never occurs as an epizootic excepting among 

 horses at grass, and then only affects those foreign to the 

 country, home-bred stock having complete immunity. The 

 disease has been described by Hutcheon in Cape Colony, 

 Theiler in the Transvaal, and Verney in Natal. The 

 intensely jaundiced condition is due to the liver getting rid 

 of the broken-down red corpuscles. 



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