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Questions

1.  There are two common species of black scour worm, which one is more pathogenic and in what environments is it more common? 

2. How can you use a paddock while it is being made low worm-risk?  

3. When hand jetting, what is a good indicator that the jetting fluid is being applied effectively?

4. Describe the withholding periods that apply to fly treatments.


A scour worm larva.
A scour worm larva.

Answers

1. There are two common species of black scour worm, which one is more pathogenic and in what environments is it more common?

Trichostrongylus colubriformis and Trichostrongylus vitrinus are the main species causing disease. T. vitrinus is considerably more pathogenic than T. colubriformis, meaning that sheep or goats need to be treated at lower egg counts.

Generally, T. colubriformis occurs in the warmer summer rainfall areas while T. vitrinus occurs more frequently in winter rainfall areas.

2. How can you use a paddock while it is being made low worm-risk?  

  • Grazing paddocks with cattle
  • Cropping
  • Haymaking
  • New pasture establishment
  • Grazing with sheep within the protection period of an effective drench

3. When hand jetting, what is a good indicator that the jetting fluid is being applied effectively?

The addition of a scourable food dye such as Permicol Blue®, or the use of an indelible pencil can be used to check wetting. If the sheep have been properly jetted, fluid will run around the body and drip from the belly of thoroughly jetted sheep. Proper jetting for body strike protection should provide coverage for the belly, but rams and wethers may require direct treatment of the pizzle area.

4. Describe the withholding periods that apply to fly treatments.

  • The Wool Harvest Interval (WHI) is defined as the time from application of a chemical to when the wool can be harvested to satisfy Australian environmental requirements (also includes crutching).
  • The Sheep Rehandling Interval (SRI) is the time between treatment and when wool/sheep can be safely handled without the need for protective clothing.
  • The Meat Withholding Period (WHP) is the time from chemical application to when an animal can be slaughtered for domestic use.
  • The Export Slaughter Interval (ESI) is the time from chemical application to when an animal can be slaughtered for export.