224 Journal of the Department of Agriculture. 



though they 3o not naturally contract the disease themselves, die 

 from other causes, and since the farmer has rarely troubled to remove 

 dead sheep from the veld they have supplied one of the commonest 

 sources of toxic carcass .material. Sheep and cattle should therefore 

 not be reared on the same veld unless every precaution is taken to 

 keep the farm clean. 



Horses, donkeys, and most other live stock are also susceptible 

 to the toxin but, like sheep, do not contract lamziekte because they 

 do not develop pica. 



The susceptibility to pica is therefore an important link in 

 explaining why lamziekte is dominantly a disease of cattle, and why 

 it is so rarely reported in other animals. Other animals only get it 

 by accident. 



In regard to the susceptibility to the toxin itself, the main 

 practical bearing as it affects cattle concerns the possibility of 

 establishing an immunity. 



Of the six links in our chain each one is equally important from 



a general scientific point of view. From a practical point of view 



'the most important link is the one we can break most easily and most 



cheaply. But since we are not yet quite certain which this is, the 



problem must be studied as a whole in a broad scientific spirit. 



Any one effective break is sufficient to eradicate lamziekte, and 

 the reason why the disease is not rampant over greater areas in South 

 Africa than is actually the case, is simply that there are many places 

 in which the chain happens to be naturall}- broken. It is a well- 

 known fact that lamziekte has been steadily spreading over the 

 country and appearing on farms where it was formerly unknown. 

 This is because one or other of the missing links is supplied by the 

 operation of some other cause, and one of the preventive measures of 

 the future may well take the direction of blocking the insertion of 

 missing links into new areas. 



Whether the control of lamziekte in the known lamziekte areas 

 will be sufficient to prevent its spread to areas now healthy, depends 

 altogether upon the method of control adopted. Thus, if the method 

 adopted is the complete destruction of all carcass material (Link 

 3), then lamziekte could never spread. But if the chain were 

 only broken by an immunizing process (Link 6) it would not 

 completely prevent the spread. It would only protect the individual 

 animal but would not remove the cause. 



To break Link 2 of the chain without breaking Link 3 

 is practically impossible, since tli^ organisms are sporulating ones 

 and infect the soil. Once into the soil we have no practical method 

 of dealing with thein, although they may die out of their own accord 

 in the course of years if, by removing all carcass material, they are 

 prevented from multiplying. 



It may well happen, however, that Link 2 is naturally absent 

 in certain areas. It this is so, and the toxicoe'enic saprophytes, i.e. 

 the particular bacteria which elaborate the poison from the decaying 

 animal remains, are absent on any farm, there can be no lamziekte. 

 Carcasses then undergo the ordinary non-toxic type of putrefaction 

 occasioned by ordinary harmless bacteria, and the rotten bones, bits 

 of hide, flesh, etc.. do not produce the disease even if the cattle have 

 pica and eat the obnoxious material. This is a state of affairs which 



