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Resistance to drenches in sheep internal parasites - Answers

1. The first paragraph in the Farming Ahead article above, claims that the overuse of drenches is one of the most obvious causes of the development of resistance to drenches by worms. What do you think is meant by 'overuse of drenches'?
   Overuse of drenches means using a drench more often than prescribed in the instructions for the use of the drench.
   
   
2. Find out what is meant by ad hoc, so that you can explain what is meant by 'For many years treatment for worms was fairly ad hoc'.
   Ad hoc means impromptu or made in an emergency situation. This means that ad hoc drenching was done as a response to problems or as an impromptu decision, not as a planned operation, timed to achieve maximum result and coincide with other control methods.
   
   
3. Contrast ad hoc drenching with the Wormkill program that is described in the Controlling sheep internal parasites section. Describe how these two methods differ.
   Ad hoc drenching differs to drenching according to the Wormkill program, in that the Wormkill program only drenches three times a year and involves other methods of worm control. The timing of the drenches in Wormkill are planned in order to achieve the maximum effect with the limited use aimed at reducing the chance of worm resistance.
   
   
4. What do you think would occur if a farmer who was experiencing problems of worm resistance to a drench, failed to change the type of drench he or she was using?
   If a farmer was experiencing resistance to a drench and he or she failed to change the type of drench being used, the worm burden (number of worms infecting the sheep) would continue to increase.
   
   
5. What do you think 'dose to the heaviest in the mob' means?
   'Dose to the heaviest in the mob' means that one dosage should be used for each mob of sheep drenched and this dosage should be calulated according to the weight of the heaviest sheep in the mob.
   
   
6. What is a 'sublethal' dose of drench?
   A 'sublethal' dose of drench is an amount of drench that is too small to kill a significant number of worms.
   
   
7. This Farming Ahead article suggests another method of controlling worms, a long-term method of worm control. What is this method of worm control?
   The Farming Ahead article suggests a long term method of worm control in sheep could be breeding sheep that are resistant to worms.

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