Online learning: Checking for lice

Checking sheep regularly and thoroughly for lice is an essential tool for maintaining a lice-free flock.

Structured reading

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Monitoring sheep for lice
A description of how to properly go about checking a mob and individual sheep for lice.

Causes of rubbing in sheep
Description of conditions aside from lice that will cause sheep to rub their fleeces.

Itch mite in sheep
Description of itch mite, its diagnosis and control.

Rubbing Tool
An interactive tool that allows users to determine the cause (or causes) of rubbing in their sheep. 

Question and answer

For those who prefer a problem based approach to learning, answer the following questions.
Each of the questions below links further down the page to the answers.

Questions:

  1. How often should existing sheep on a property be checked for lice?
  2. When buying rams, what is recommended to avoid introduction of lice?
  3. What should you do when straying sheep have been returned by the neighbour?
  4. Which sheep in the mob are the best candidates to check for lice?
  5. Aside from lice, what else causes sheep to rub?
  6. How do you go about checking each sheep for lice?

Answers:

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

1. How often should existing sheep on a property be checked for lice?

All mobs should be checked for lice at least twice each year. Useful opportunities for monitoring are when sheep are yarded for drenching, crutching, marking and shearing or other management procedures. Any sheep seen with rubbed fleece or pulled wool should be checked as a matter of urgency. It is also a good idea to ask your shearers and shed hands to look out for lice at shearing. Make sure to check every mob on your property, including the killers and rams.
 

2. When buying rams, what is recommended to avoid introduction of lice?

All newly purchased sheep, agisted sheep or sheep returning from other properties should be inspected before release onto the property. New rams can pose a significant risk, but are generally introduced only in small numbers; therefore, an automatic policy of shearing and off–shears treating rams for lice on arrival (use a product that will kill lice before the rams are joined) is recommended.

 

3. What should you do when straying sheep have been returned by the neighbour?

Any stray sheep found in the mob or returned after straying should be closely examined for obvious lice. However, lice may be present, but not found if:

  • shearing has occurred in last 3–6 months, as this will remove most, but not all, lice. The lighter the infestation was before shearing, the longer it will take to become visible again.
  • A long-wool lice treatment has been applied in the last 3–6 months, as long-wool treatments will kill many lice, but cannot eradicate all of them. The lighter the infestation was before treatment and the more effective the treatment product used and application method employed, the longer it will take for lice to become visible again.
  • A short-wool lice treatment has been applied in the last 3–6 months, but has either been only partly effective (some of the lice are resistant to the treatment product) or it has been applied poorly or some sheep missed treatment, so some lice have survived in the flock. The lighter the infestation was before treatment and the better the product and application or fewer sheep were missed application, the longer it will take for lice to become visible again.
  • The sheep has acquired a very small infestation of lice (it contacted other lousy sheep for only a very short time and/or the lousy sheep themselves had only a very light infestation), which will take a considerable time to build up to visible levels.
  • The sheep was only in contact with lousy sheep—even heavily infested—in the last few months, so the new infestation has not had time to build to visible levels.

Management options range from a high risk, where the sheep are returned to their mob, through various quarantine and treatment options, through to immediate disposal of the sheep (least risk).

 

4. Which sheep in the mob are the best candidates to check for lice?

Look for sheep showing signs of rubbing or biting at their fleece.

Rubbing is a very powerful indicator of lice infestation and sheep will begin to rub with quite low lice numbers. Rather than inspecting random sheep, time is most efficiently used by carefully going through the mob to identify any sheep with even a small amount of rubbed or pulled wool, although the worst-rubbed sheep should be checked first.

If on thorough inspection, sheep are not rubbing, lice may still be present, but in such low numbers that it will be almost impossible to find them and fleece damage will be minimal anyway.

If there is a concern that the sheep may have become infested with lice or that the last treatment was not effective, check again for rubbed wool in another month—or if shearing is within a month, treat off-shears for lice anyway as a small infestation without treatment will increase and is likely to reduce the value of next year’s wool clip.

 

5. Aside from lice, what else causes sheep to rub?

Other causes of rubbing include grass seeds, fleece rot, lumpy wool, flystrike and itch mite. Sheep with tender wool or frequently walking through bush or long grass, and some breeds that shed their fleece may also appear to be rubbing.

Read the LiceBoss Note: Causes of rubbing in sheep or use the Rubbing Tool in Liceboss to help to diagnose other causes of rubbed fleece.
 

6. How do you go about checking each sheep for lice?

  • Lay the sheep on its side in a well-lit position, part the wool and look for lice.
  • If you need glasses to read the telephone book, make sure you use your glasses when looking for lice. A magnifying glass can help.
  • Check at least 20 wool partings on any rubbed sheep; partings should be at least 10 cm long. The more sheep you inspect, the more chance you have of finding lice if they are present.
  • Once you have found one live louse you can stop; there will be many more lice that you can’t find. All sheep should be treated after the next shearing. 

 


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