Lice in Summer Purchased Sheep

Purchasing sheep in through the summer months can often lead to lice issues later on in the year. Summer sheep purchases are generally shorn sheep which can make lice issues very hard to detect. It is always advisable to either keep introductions separate until they can be shorn and treated or do so as soon as they arrive. A helpful resource for developing a property biosecurity plan can be found at

When choosing a lice treatment option, it is important to rotate the different chemicals, rather than use the same treatment year after year, to reduce the chance of chemical resistance. As only a few chemicals that do not have documented lice resistance.

There are a few different options in terms of both application method and chemical group. Saturation treatment methods like plunge dipping will give the best coverage for treatment, however backlining is often more convenient. Using a backline after shearing is popular especially for those with smaller flocks due to the ease of treatment. When treating sheep with a backline, it is important that the treatment is done correctly to ensure success. They generally must be applied within 24 hours of shearing and as a short wool treatment and should only be used on any sheep that are shorn cleanly and are free of dermo. Remember, most new age backliners require two stripes down the backline to avoid inadvertently missing one side. Backliner products often have a label recommendation for long wool treatments, but it is important to note that applications dose and method may vary, and long wool treatments cannot guarantee eradication of lice.

There are a few common mistakes to avoid during treatment to ensure that successful eradication of lice is achieved. If there are lambs at foot make sure they are treated as well as the ewes, otherwise the lambs will simply spread lice back into the mob. Follow product directions and make sure the product you are using is registered for lambs at foot. Do not use a backliner if the ewes are due to lamb within the next six weeks. Backliners take several weeks to control lice and depending when the first lambs are born can still catch lice and then spread it back through the ewes. If you have a split shearing, the treatments will only be effective if you can keep your treated and untreated mobs separate.

The Lice Boss website has a good product and application selector tool, which can help you decide on the best chemical control measure for your circumstance.

Remember it is an offence to have lousy sheep in a public place. This includes putting your sheep into a saleyard (even if they are in transit) and allowing your sheep to stray off your property onto roads or neighbouring property. If you would like a second opinion on identifying lice or want to report stray lousy sheep please contact your local Animal Health Adviser whose details can be found on the PIRSA website.

Jessie Thomson – Animal Health Adviser