242 Journal of the Department op Agriculture. 



Class of Animal and Susceptibility to Disease. 



It has already been slated tliat most animals, including- sheep and 

 horses, are susceptible to the lamziekte toxin, but never contract the 

 natural disease simply because they do not develop pica, and hence, 

 never, except by accident, ingest obnoxious material. For practical 

 purposes, excluding- the stray natural cases amongst goats, ostriches, 

 and poultry, cattle come into almost exclusive consideration. 



At this point, therefore, it is only proposed to refer to the 

 possibility of breaking the etiological chain by reducing the suscepti- 

 bility of the beasts threatened with the disease; ^'n other Avords, by 

 immunizing them against the toxin which they are liable to ])ick up 

 from the veld. There is a possibility of doing- this by injection of a 

 modified toxin and so engendering an anti-toxin in the body of the 

 animal. This problem is a difficult one, since nature, and not man, 

 confers immunity. Experience has shown that any natural immunity 

 which exists towards the toxin is of very short duration, and cattle 

 which have just recovered from one attack of lamziekte can succumb 

 to pnother very soon after. But it is just theoretically possible to 

 build up an experimental immunity of longer dumtion and perhans 

 devise a scheme whereby a temporary immunity could be made to tide 

 over an urgent period, and so gain time to break the chain of 

 causation at another link. 



This line of attack is being" vigorously pursued, but it is too soon 

 to hold out any prospect of success. 



Although it is desirable for the control of lamziekte to have as 

 many ways of breaking the etioloarical chain as possible, it must asfain 

 be emphasized that only by breaking Link 3, i.e. removing 

 material out of which the toxin is manufactured, can the cai/se he 

 revioved. Attack at Link 6, i.e. decreasing the susceptibility 

 of the animal, can only protect the particular aninml immunized, 

 and that probably only for a very short time. It will not prevent 

 toxin production, which can occur in carcasses of animals dying from 

 other diseases or from drought, and which therefore can spread all 

 over the couniry irrespective of the use of a possible lamziekte 

 vaccine. All efforts to clean the farm must therefore be made, and 

 in the process the farmer can comfort himself with the reflection that 

 he is not only stamping- out lamziekte, but other diseases, such as 

 anthrax, as well. 



The degree of success depends upon the ene'"-'- of the farmer 

 himself; At Armoedsvlakie, where the mortality from lamziekte was 

 30 per cent, in 1914, the mortality with a herd of 500 cattle was 

 reduced to below 2 per cent, after the measures here advocated were 

 adopted in 1919. 



CONCLTTSTON PRACTICAL MeASUBES FOR PREVENTION. 



'Ihis article may now be concluded with a few provisional 

 I)ractical directiojis for control, based upon the lueasures followed at 

 Armoedsvlakte diii-iug the last season. They will be improved upon 

 later, but for the jjiesent they will be found servicoable. They may 

 })e addressed personally to tlie farmer who has suffered most heavily 

 from lamziekte in the past:^ — • 



1. Clean your farm of all bones and carrion and Icee}) it clean. 



For this purpose it is necessary to secure all rarcass inaterial of 

 the animals which die on the farm and deposit it in some safe place, 



