Online learning: Sheep lice

A basic understanding of the biology of lice will assist you in identifying and controlling them.

Structured reading

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About lice
A brief description of the lice and their economic effects.

Biology of sheep lice (Bovicola ovis)
Lice, their effects, life cycle, spread sources, their build up and distribution.

Why control sheep lice? Economic effects of lice on production
A description of how lice affect sheep and the associated production costs.

Question and answer

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Questions:

  1. How many species of lice occur on sheep in Australia?
  2. Do goat lice breed on sheep?
  3. What effects do lice have on fleeces?
  4. How does temperature affect louse reproduction?
  5. In what situations does transfer of lice from one sheep to another best occur?
  6. Where are lice typically found on sheep?
  7. What factors affect louse numbers?

Answers:

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


Figure 1. Sheep lice. Source: Peter James
Figure 1. Sheep lice. Source: Peter James

1. How many species of lice occur on sheep in Australia?

Three. The sheep body louse (Bovicola ovis, formerly called Damalinia ovis) is a pale yellow insect 1.5 to 2 mm long with brown transverse stripes on the abdomen and a broad, red-brown head (Figure 1). It is a chewing louse and feeds on skin scurf, lipid and sweat gland secretions, superficial skin cells and skin bacteria (Sinclair et al. 1989). Males are smaller than females and have more pointed abdomens.

Sheep are also host to three other species of lice. The sucking lice feed on blood, have long thin heads and appear bluish in colour: the face louse, Linognathus ovillus, occurs mainly on or close to the face, and the foot louse, Linognathus pedalis, is found on the legs and on the scrotum in rams.

2. Do goat lice breed on sheep?

Goat chewing lice, Bovicola caprae have been found on sheep running together with goats, but do not appear to breed on sheep.
 

3. What effects do lice have on fleeces?

Infestation with sheep lice can reduce clean wool cut by up to 1 kg per head. Lice also reduce yield, cause fleeces to become cotted and yellow and result in increased losses during processing. In New Zealand, sheep lice have been shown to cause a defect in sheep leather known as cockle. This is manifest as multiple, sometimes discoloured, lumps visible in sheep leather after processing. Infestation with B. ovis does not affect fibre diameter and, contrary to popular belief, does not cause reduction in body weight.
 

4. How does temperature affect louse reproduction?

Development occurs only at temperatures between 30°C and 39°C and the incubation period is generally between 9 and 11 days. Temperatures of greater than 45°C will rapidly kill eggs.
 

5. In what situations does transfer of lice from one sheep to another best occur?

Lice move to the surface of the fleece when it is shaded and warm. Transfer between animals occurs when sheep are in close contact, such as when they are shedded, held together in yards, or perhaps when feeding or drinking from a trough. It is fastest

  • When sheep have short wool
  • With management practices that increase the amount of close contact between sheep,
  • When sheep are held tightly together in sheds or yards that are shaded.
  • When ambient temperatures are moderate, neither cool nor very hot.
     

6. Where are lice typically found on sheep?

Lice can be found on most woolled areas of sheep, although they are rare on the belly and don’t appear to breed there. They are not evenly spread, but have a clumped or aggregated distribution. At most times of the year densities of lice are highest along the sides and sometimes on the back of sheep. At times, significant numbers of lice can also be found on the head, underlining the importance of thorough coverage when dipping sheep or applying backliners.

After shearing, a greater proportion of the population are found at sites on lower body regions such as under the neck, lower flanks and upper legs and in areas where the wool has not been closely shorn.
 

7. What factors affect louse numbers?

  • Time from infestation
  • Shearing
  • Temperature
  • Solar radiation
  • Rainfall
  • Sheep susceptibility to lice
    • Breed
    • Differences among sheep within breed
    • Age
    • Sheep health and nutrition

 


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