Developing a sheep lice biosecurity plan
Developing a lice biosecurity plan requires an understanding of how lice spread and strategies to prevent introduction.
The main components of a lice biosecurity plan are to:
- commit to preventing lice being introduced
- identify risks of introducing lice
- apply preventative measures or change management strategies
- monitor stock for signs of lice.
Good biosecurity will not only prevent the introduction of lice and consequent costs, but avoid problems with lice which are resistant to specific chemical treatments.
Commit to preventing lice being introduced
The first step is to ensure adequate time and resources will be committed to preventing an initial lice infestation on your property. Once you have established a lice biosecurity program, review and assess it at least every two years to ensure it is still effective. The main area to reconsider is the risk assessment because risk levels may change. For example, a neighbouring property may become infested or may increase trading.
As sheep lice prevalence is high, it is important to take steps to avoid bringing lice onto a property when buying sheep, including rams. It is more likely that buying sheep directly from a property that has an established biosecurity plan will present less risk of introducing lice onto your farm than buying sheep through a saleyard.
Collaboration with neighbouring and local farmers can greatly reduce the risks of lice being introduced. Where neighbouring farmers shear and treat at a similar time, the sources of re-infestation in an area will be reduced. Advisers may be able to provide technical advice to assist local lice action groups.
Identifying risks of introducing lice
Identifying high risks and implementing strategies to minimise these will greatly reduce the risk of lice and associated costs.
Stray and introduced sheep
Almost all new sheep lice infestations occur through lousy sheep entering a property. It is well worth keeping all paddock gates shut for this reason. Reclaiming your own sheep after they have strayed from your property can also increase the risk of introducing lice onto your farm. Straying sheep pose a very high risk as they may not show obvious signs of being infested, but enter and leave the flock undetected. Without flock monitoring, returned strayed sheep may have undetected infestations. Early detection of an infestation can limit spread to other flocks.
The second major means of introducing lice is via purchased stock, which may not show obvious signs of a lice infestation. When lice prevalence is considered high, any bought-in sheep pose a risk of lice introduction and should be managed accordingly.
National Sheep Health Declaration
When buying sheep consider those offered for sale with a National Sheep Health Declaration (NSHD). This details whether there has been any evidence of sheep lice at or since the last shearing, the date of last shearing and name and date of any external parasite treatment used. The buyer can use this information to make a decision on whether to continue with the purchase and to assist decision-making on treatment and quarantine measures needed until the buyer can be certain that the purchased sheep do not have an infestation.
There may be some situations such as on-property ram sales, where you can ask the vendor whether their sheep may have or had lice recently and the details of chemical treatments used. Be aware that some treatments registered for lice such as insect growth regulators and synthetic pyrethroid are no longer fully effective and consequently may not reliably eradicate lice on all properties. When this discussion confirms that the purchase will proceed, plan to either quarantine and monitor the flock for three months, or shear, treat, quarantine and monitor as required.
Rams pose a frequently overlooked risk, as they are often purchased close to joining, which restricts the time available to monitor for signs of lice.
Research has shown that lice may survive for a few days on shearers’ moccasins. If shearers have come from a property where lousy sheep were shorn, ask them to change their clothes and moccasins before entering your shed.