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Where have all the lice gone, long time parting?


Dr Paul Nilon, Nilon Farm Health, Tasmania (pandonilon@bigpond.com)

Those with grey hair and a curmudgeonly outlook will remember the 1960s PP&M classic, which is the inspiration for this piece.

A client rang to say he had lice in his sheep. Both he and his manager had seen them scuttle away while parting the fleece. So, a consultation was scheduled to discuss treatment options. As rubby sheep were in the yards, I took the opportunity to refresh my arcane fetish for finding lice. I saw a single louse on the first parting. After that, I couldn't find any despite multiple partings on many sheep, and in spite of the mob being visibly rubbed, with some individuals starting to cott up.

Checking 20 partings on at least 20 and up to 40 sheep requires a big investment in time.
Checking 20 partings on at least 20 and up to 40 sheep requires a big investment in time.
Lice are not easy to find even when rubbing is present and there is a history of exposure,
Lice are not easy to find even when rubbing is present and there is a history of exposure,

Lice are not easy to find. Even with rubbing and a history of exposure, you may come up with nothing, nout, nada, nichego, nichts (this is read internationally). So, if you suspect lice, but cannot find them here’s what to do:

  1. Stop looking, go home and pour a large scotch and listen to PP&M as linked above. It’s surprising how a scotch improves the diagnosis rate.
  2. Review  Jenny Cotter's excellent article on how to look for lice and your chances of finding them. Remarkably, even when lice numbers are high, your chances of finding them on a single sheep with 20 partings is 60% or less. I know from watching clients that many only do a few partings on a few sheep. Inadequate! Look at 20 partings on at least 20 and up to 40 sheep. This requires a big investment in time.
  3. If you still cannot find lice what you do next depends on the risks. Fine wool flocks may decide to treat speculatively with a knockdown (spinosad or ivermectin). An alternative is to wait 10 days–2 weeks and reinspect. Quarantine the mob and start inspecting in-contact mobs. Assuming it is not lice, is a poor option.
  4. Start planning what you will do on the assumption that lice will be found. The options include (but are not limited to):

    a. early shearing with a return to normal time next year

    b. genuine prem shearing with a new shearing date or perhaps 2 shearings per year. Many Merinos are pushing the boundary of overlength wool (say, 130 mm) with a single shearing. Consult your broker for help on that one

    c. knockdown treatment and quarantine of treated mobs

  5. Only after 2 clean mob inspections can you be confident of no lice. Even so, remain paranoid and vigilant.

And as for PP&M, you may be interested to know my brother is Peter and sister is Mary. The burden of being a child of the ’50s!

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