Sheep Lice Management
Regular checking of your sheep for the signs of lice is important if infestations are to be identified early. Sheep can be infested with lice without showing overt signs, so it is important during regular flock checks to catch some sheep for a closer inspection. To check sheep, choose somewhere with good light and look for lice along the sides of the neck, body and rump. Select sheep that are showings signs of rubbing. Part the fleece 20 times per side each parting being 10 cm. Adult lice are readily visible with the naked eye
Sheep lice are obligate parasites, which means they spend their entire lifecycle on sheep. Lice feed on flakes of dead skin, secretions and bacteria normally found at the surface of the skin. This causes irritation and therefore sheep bite, rub and pull at their wool. Signs of a sheep lice infestation includes cotted, discoloured fleece, fleece derangement, reduction in fleece weight, wool stuck in fences and scouring yield.
The main way lice spread is via direct contact between sheep so good boundary fences are crucial to keeping stray sheep out. However, not all introduced sheep get in unintentionally. Other sources of infestation include shearing sheds where lice can survive for up to 2 weeks and on clothing and shearers’ footwear. Despite common belief, tags of wool on fences are not a major source of infestation because lice do not survive long under these conditions.
A number of common farm practices can make lice control more challenging. Split shearing can result in treated clean sheep coming in contact with untreated, infested sheep unless strict separation can be maintained. Failure of clean shearing, for instance due to skin infections such as lumpy wool or “dermo” can reduce the efficacy of lice treatments and should be addressed.
In general, all introduced sheep need to be quarantined until they are shown to be free of lice or treated appropriately. If introduced sheep are treated for lice, keep them apart from any clean sheep for 6 weeks to allow time for the treatment to kill all lice on them
To treat lice, the best method is to treat them with either a pour-on backliner such as Cydectin or a sheep dip such as Viper, straight after shearing. Shearing them removes the bulk number of lice along with their eggs that are attached to the hair. The eggs are resistant to many brands of lice treatment, therefore shearing them and removing the hair is crucial to successful treatment.