674 MANAGEMENT OF SHEEP DISEASES 



liable to die when moved from healthy to infected ground, 

 and a fence or stream often separates the one area from the 

 other. Deaths from several of the other diseases named are 

 frequently wrongly attributed to louping-ill. It exists in a 

 chronic and in an acute form. "In the former, the sheep is 

 usually convulsed at first, and afterwards more or less 

 paralysed, lying sometimes for weeks unable to rise." The 

 appetite is generally good, but few recover the power of their 

 limbs. " Acute cases run their course to a fatal issue in a 

 few hours, with symptoms of blood-poisoning." The disease 

 has been long known, but its bacterial origin was unsuspected 

 till 1 88 1, when Principal Wm. Williams, working under the 

 auspices of the Highland and Agricultural Society of Scot- 

 land, made the discovery that the sheep tick (Plate CCVA.) 

 taken from trembling sheep contained organisms identical in 

 appearance to those he found in the spinal fluid which he 

 extracted from the vertebral column of affected animals. 

 This exploded the theory of Brotherston, Botanist to the 

 Highland Society's Louping-ill Investigations Committee, 

 that ergot was the cause. The investigations of the 

 Departmental Committee did not confirm the belief in the 

 tick as the main carrier of the disease, but " show that, at 

 most, ticks can carry infection only under exceptional and 

 accidental circumstances." The facts, however, remain that 

 there is no louping-ill on land where there are no ticks ; its 

 appearance on fresh ground has been concurrent with the 

 advent of ticks ; it appears at the seasons of the year when 

 ticks are in evidence, generally in spring, but in exceptional 

 places in the West Highlands also in autumn. When ticks 

 are not numerous, or when they are killed by dipping the 

 sheep on infected land, the occurrence of trembling is at a 

 minimum. Similar blood-poisoning and paralysis have been 

 traced to the bite of a tick in South Africa and in Queens- 

 land. 1 When the ticks there are sought for and removed, 

 the animals usually regain the use of their limbs within a few 

 hours. 



The blood of affected sheep " was free from any organ- 

 ism," and inoculation with it failed to convey the disease. 



1 See the Author's works, The Rural Economy and Agriculture of 

 Australia and New Zealand, p. 333 ; and The Farming Industries of Cape 

 Colony, p. 303. 



