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Questions

1. Name two benefits of the second summer drench for sheep in temperate winter rainfall regions?

2. Name the three tests that are based on counting worm eggs and their purpose. 

3. Name three principles you should consider to manage treatment-resistance in lice.

4. What threshold level of flystrike would you use to determine when to initiate control treatments after a dry period?


During high risk times for flystrike, check sheep regularly and thoroughly for strike.
During high risk times for flystrike, check sheep regularly and thoroughly for strike.

Answers

1. Name two benefits of the second summer drench for sheep in temperate winter rainfall regions?

The drench is given to remove the worm burden from sheep. Consequently, little contamination in the form of worm eggs will go onto pastures at a time when pastures are dry and larval survival will be low.

Most importantly, the level of contamination on pastures in autumn is a strong determinant of the peak larval availability in the following winter, and of subsequent scour worm problems. The second summer drench, therefore, will reduce contamination on pastures and provide good worm control.  

The second summer drench is given in January or February and is based on the results of a WormTest. It is not routinely needed in some areas, nor all years.

2. Name the three tests that are based on worm egg counting and their purpose.  

The three tests are the WormTest, the DrenchCheck and the Drench Resistance test.

i. The WormTest is used to monitor stock to determine if they need to be treated for worms. WormTest monitoring is done more often during a wet season, or less often during a dry season. WormTests are also conducted at strategic times based on your location.

ii. The DrenchCheck is two WormTests, one conducted before drenching and the other 10-14 days after drenching. The results demonstrate how well the drench has worked when the post-drench egg counts are compared to the pre-drench counts.

iii. Drench Resistance testing is an on-farm trial to determine the efficacy of a number of drenches against the worms on your property.

3. Name three principles you should consider to manage treatment-resistance in lice.

Some general principles to prevent or delay the development of resistance include:

  • Make certain that backline products are applied strictly according to label directions and that sheep are treated at dose rates calculated for the heaviest sheep in the mob.
  • Ensure that every sheep is treated evenly along the middle of the backline from head to rump.
  • If a long wool treatment is used, ensure that a chemical from a different chemical group is used at next shearing.
  • Generally, it is a good idea to rotate products from different chemical groups at consecutive treatments.
  • Don’t mix treated and untreated sheep, particularly if there is a chance that the untreated sheep may be carrying lice. Don’t forget lambs.
  • If a chemical breakdown is suspected, use the Treatment Tool in LiceBoss to see if a management reason (e.g. stray sheep, incomplete muster, wrong dose rate, and incorrect application) could be the cause. If no reason can be found, discuss this with an adviser or chemical company representative and be sure to treat all sheep with a product from a different chemical group at the next shearing.
  • If treatment for flystrike and lice is required in the same year, use chemicals from different chemical groups.

4. What threshold level of flystrike would you use to determine when to initiate control treatments after a dry period?

Once about 0.5% of sheep (1 sheep in 200) are struck in any one week, treatment is initiated. 

It is almost always most economical to treat the whole mob with a preventative treatment, as the costs of labour for monitoring and treating individuals are very high, as are the costs from deaths and severely struck sheep.

In this season, isolated rain events have caused conditions that are currently increasing the fly-risk. Producers then need to determine if it is likely to be more economical to continue treating affected sheep individually over the next few days or apply a mob treatment.

If you are close to shearing or the sale of animals and the various withholding periods for mob treatments will exceed the time until shearing/sale and, if the flystrike risk is severe, consider bringing shearing forward or applying a product with a very short withholding period.