Online learning: Preventing new lice infestations

Nearly all new infestations begin from contact with infested sheep. A good biosecurity plan is essential for keeping lice out.

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Preventing new lice infestations
Introduction to prevention of lice infestations.

Sheep lice—biosecurity can prevent introduction
Planning your biosecurity plan to prevent lice introduction.

Question and answer

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Questions:

  1. What infrastructure is essential to good biosecurity?
  2. What are the four key components of a successful lice biosecurity plan?
  3. What are the 3 sources of possible lice introduction?
  4. When purchasing sheep what factors about the origin of the sheep, or the sheep themselves, increase the risk that the purchased sheep will have lice?
  5. If sheep are being brought onto the property, what are your options to manage lice?
  6. How long does it take for signs of lice infestation to become obvious?

Answers:

You can also click on each question below to go to WormBoss pages with related information.

1. What infrastructure is essential to good biosecurity?

Stock-proof fences are essential for good biosecurity. Without them, straying sheep can bring lice onto the property and isolation/quarantine of introduced sheep becomes impossible.
 

2. What are the four key components of a successful lice biosecurity plan?

  • Commitment to preventing lice being introduced
  • Understand lice biology and how lice spread
  • Recognition that all introduced sheep present a possible risk of introducing lice
  • Awareness that communication within the local community assists lice biosecurity
     

3. What are the 3 sources of possible lice introduction?

  • Stray sheep
  • Purchased sheep
  • Non-sheep transmission
     

4. When purchasing sheep what factors about the origin of the sheep, or the sheep themselves, increase the risk that the purchased sheep will have lice?

1. They are from a high risk source property, which has one or more of these

  • regularly trades sheep
  • poor fences
  • crossbred lambs that tend to stray
  • no active monitoring
  • no stock introduction policy*
  • neighbours infested
  • inability to get clean muster
  • split shearings

2. The sheep themselves are high risk introductions because

  • known lice present and treated
  • suspect lice and treated
  • unknown louse status e.g. saleyard

3. They are from a district that has a high local lice prevalence
 

5. If sheep are being brought onto the property, what are your options to manage lice?

A good biosecurity plan must assume that introduced sheep are infested with lice regardless of their history or whether there are no lice or signs of lice. Your decision on how to manage the introduced sheep will be a risk management choice. This is based on

  • The number of sheep being introduced, the cost of their treatment and impact of out-of-season shearing compared with the cost and impact of treating the whole flock if lice spread to them.
  • Your ability to properly quarantine the introduced sheep until 2–4 months (depending on the product active) after off-shears treatment.

Management options in descending order of biosecurity rigour are:

  1. Shear and apply an off-shears treatment, then quarantine for a minimum of 2–4 months (depending on the product active).
  2. Sheep introduced with less than 6 weeks wool should have an off-shears treatment applied, then be quarantined for a minimum of 2–4 months (depending on the product active). Note: this may produce high wool residues if the sheep have already been treated off-shears.
  3. Quarantine introduced sheep until after they receive an off-shears treatment at their next shearing. Quarantine should continue for a minimum of 2–4 months off-shears (depending on the product active). Introduced sheep with more than 6 weeks wool may require a long wool treatment to suppress (not eradicate) lice; consult the Long Wool Tool to see if this is warranted (ensure treatment adheres to wool rehandling and harvesting intervals).
  4. Don’t apply quarantine or treatment to introduced sheep. Then treat the entire flock off-shears, or if lice or signs of lice are not detected consider not treating.
     

6. How long does it take for signs of lice infestation to become obvious?

It takes at least 3 months from the time of initial infestation for rubbing to become obvious.

 


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