The Life-History of the Wire-Worm of Sheep. 329 



buck), experience lias shown that these animals are only rarely 

 infected, and hence systematic dosing of sheep and goats is generally 

 sufficient to eradicate the infection. In the rare cases in which 

 infected buck, with which dosing is impossible, do keep the infection 

 alive, periodic dosing of the sheep and goats may have to be continued 

 indefinitely. It must be remembeved that the Wire- Worm Remedy 

 is a cure and not a preventive. It kills the worms in the stomach, 

 but of course passes out of the stomach with the food, and hence 

 cannot prevent reinfection. There is, therefore, no practical way of 

 preventing reproduction of the worms except l)y killing them off 

 regularly once a month until the source of infection on the veld itself 

 disappears. 



It may be added that the directions for use of the Government 

 Remedy are arranged to eradicate worms as completely and quickly 

 as possible, without danger of poisoning the sheep. They are there- 

 fore more drastic than most remedies upon the market, especially in 

 regard to preliminary starvation treatment. Even if used under the 

 less drastic conditions advertised for other remedies, however, the 

 Government Remedy is as effective as any of them. 



Analogy with Tick Eradication. — The principle undf'rLving those 

 recommendations will perhaps be clearer if it is compared with the 

 princi])le of tiadication of ticks. Ticks cannot be prevented from 

 attaching themselves to stock, and cannot be killed out in the grass 

 by any feasible metliod. The stock therefore collect the ticks, but if 

 the stock are regularly dipped the collected ticks are either destroyed, 

 or do not lay fertile eggs, and hence do not perpetuate the infestation. 

 Tlie ticks which do not attach themselves to stock die a natural death 

 in course of time, and hence after a year or two of regular dipping, 

 the farm becomes clean. In the same way, the sheep collect the 

 wireworm larvae, and the dosing destroys them. In the case of 

 ticks, short intervals between dippings, three to fourteen days accord- 

 ing to the kind of tick, are necessary because the ticks breed very 

 quickly after attaching. In the case of wire-worms an interval of 

 tiiree io io^)! weeks betwecL dosings is sufficient to prevent breeding. 

 If the dosing is systematically carried out, the wire-worms will be 

 rapidly reduced to negdigible numbers, just as ticks are reduced by 

 dipping. 



Diagnosis by Means of Culture. — A practical and easy method 

 of finding out the extent to which sheep are infected with wire-worms, 

 even before they show the ill effects of the infection, is to cultivate 

 the eggs from the droppings and observe the migrating larvae. Every 

 farmer can do this for himself by simply collecting fre>h moist 

 dropT3ings from the suspected sheep, placing them in a glass jam-jar. 

 placing the jar in a co.ufortably warm cupboard, and watching events 

 from day to day. Provided the droppings have been sufficiently 

 moist, a fine dew deposits on the sides of the glass, and from the 

 fourth day onwards the larvae, which have developed from the eg^gs 

 passed out by the sheep in the droppings, begin to migrate and form 

 slimy white tracts ramifying over the surface of the glass. If the 

 glass is now exposed to strong light the larvae wifi be observed to 

 return to the droppings, and enter them again provided they are still 

 suffidently wet. It should be added tha'; " sour faeces "' are unsuit- 

 able for culture, but that in most cases the experin>eat is successful, 

 instiuctive. and useful. 



