Not-so-Lice

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Shearing makes sense as a time to treat lice because this removes about 80% of the lice on the sheep and the bulk of lice products are most effective ‘off shears’ (within 24 hours of shearing).

There’s an array of lice treatments depending on whether you’re jetting or using pour-ons. The jetting products Extinosad (ACVM A008206) & Seraphos 1250 (ACVM A004265) can be cheaper but getting a 100% kill is unlikely as sheep never get saturated enough.

Off-shears pour-on products are Zapp Encore (ACVM A010400), Magnum (ACVM A007704) and Expo Pour-On (ACVM A010205). The IGR in Magnum and Zapp Encore gives persistent activity for 2-3 months. With Zapp Encore there is also a knock down imidacloprid which gives instant kill, this differentiates Zapp Encore from other straight IGR based chemicals. However, it does have limitations with covercomb shorn merinos. Double dose Expo Pour-On seems to be the best knock-down for lice in fine wool. The trick when applying pour-on treatments is poll to tail application and getting it evenly down the middle of the back. If the backline is only down one side, don’t expect it to kill the lice on the other side.

The essential components of an effective lice control are ...

  • Treat 100% of the animals

  • Ensure 100% of applications are done well

  • Use product that is 100% effective against lice

If you are serious about eradicating lice, bringing new sheep on property or treating with long wool, this is where Flexolt (ACVM A011971) could really help. Plus, being a new product there is no resistance out there yet. Meanwhile, if you’ve used the same product for the last few years, it’s probably worth switching it up to minimise resistance to lice treatments.

Remember, most people with lice on farm this year will have lice on farm next year, so it is often the practices around lice management making it tricky to get rid of.