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Control lice with surveillance and ‘social distancing’

23 July 2020

Lice are a costly problem for sheep producers but they can be controlled through regular surveillance and good farm biosecurity.

While the biggest impact of sheep lice is fleece damage in Merinos, Tasmanian livestock consultant and former ParaBoss* Technical Committee member Paul Nilon said lousy flocks face control costs and reduced marketing options, regardless of breed.

“Lice infestation can easily reduce fleece weights by up to one kilogram, but the critical thing is the fleece derangement caused by rubbing and pulling,” Paul said.

“This destroys the value of your clip – it may well be halved if lice are left unchecked.

“There’s also the impact on your trading options. No one wants to buy lousy sheep.”

In rare cases, lice infestations can be so extreme they affect animal health and welfare.

Manage contact

Social distancing isn’t just important during global pandemics – almost all new lice infestations begin from contact with infested sheep, so it’s a good place to start to prevent lice.

“If you want to be lice‑free, you need a good lice biosecurity plan which prevents contact with infested sheep,” Paul said.

Producers who can’t realistically aim to be lice‑free – for example, lamb traders and producers with large bush blocks where it’s hard to get a clean muster – should aim for proactive surveillance and have a plan to manage incursions.

Paul recommends only treating for lice if they’ve been detected (with some exceptions for high‑risk situations).

Treating after every shearing, even if sheep don’t have any signs of infestation, is an unnecessary expense and creates a false sense of security as residual protection provided by most lice treatments is only a matter of weeks.

“Treating speculatively doesn’t replace the need for strict, ongoing surveillance,” he said.

“It also unnecessarily increases chemical residues in your wool, which may limit marketing options, and may contribute to pesticide resistance.”

Six steps to a licefree flock

Here are six practical tips to prevent and manage lice:

  1. Develop a lice biosecurity plan for your property. The LiceBoss website has guidelines.
  2. Use the Sheep Health Statement – if it shows there have been recent lice treatments, ask why. If the vendor is not prepared to tell you why they had to treat for lice, either discount the sheep heavily or don’t buy them. If possible, inspect sheep before purchase. When introducing sheep to your property, inspect, quarantine and monitor them.
  3. Monitor wool for signs of rubbing and fleece derangement. The LiceBoss website has a guide to monitoring sheep for lice.
  4. If lice are detected, consider your individual situation when selecting a treatment. Use the LiceBoss Treatment Guide to help with decisions such as:
    • what portion of your flock to treat
    • whether to do a premature shearing of all or part of the flock, followed by an off‑shears treatment
    • whether to do a long‑wool knockdown treatment to carry through to normal shearing time
    • which chemical group is most appropriate
    • how to respond if the infested sheep are pregnant or have lambs at foot
  5. The biggest contributor to lousicide efficacy failure is poor product application so make sure you’re doing it properly. The LiceBoss website has treatment guidelines for a range of applications, including back‑lining, dipping and jetting.
  6. Seek professional advice on treatment and control options and always inform your neighbours if you do find lice on your property.

*ParaBoss is a not‑for‑profit organisation, funded by MLA and Australian Wool Innovation and coordinated by the University of New England with industry oversight. ParaBoss coordinates WormBoss, FlyBoss and LiceBoss.

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