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Beyond the Bale : September 2010
18 WOOL PRODUCTION September 2010 BEYOND THE BALE Monitor sheep for lice Reports from most states point to a resurgence of sheep lice in the national flock. Sheep lice have been estimated to cost between $170 and $350 million annually. Yet these figures can be cut significantly if flock owners and managers elevate lice control to a 'must do' rather than an 'ad hoc' operation. AWI's animal health and welfare project manager, Dr Jane Littlejohn, says the reports of a growing lice population highlight two issues. "One is that we have spreading chemical resistance, which is a major problem, although we have the knowledge and new products to step around it. "The other issue is the unsafe acceptance that it is easier to treat every year off-shears, let lice come back during the year, then treat again the following shearing. This just creates an endless infestation pool and it can be costly if the lice are resistant to the backline treatments of the 1980s and '90s." Dr Littlejohn says it only takes one louse to start an infestation. "Female lice lay one or two eggs every three days, and live for about 30 days. If there is one louse found per every 10 centimetre fleece-parting, then the sheep can be carrying 3000 to 4,000 lice. "Sheep start rubbing with 100 lice and you have a 60 per cent chance of finding some of these lice if you do 20 partings. A heavily infested animal has 100,000 or more and are easier to find." Fleece weight can be reduced by 200grams/head for a light infestation, and up to one kilogram/head for a heavy infestation. However Dr Littlejohn says there are clear and proven steps to effective lice control. "It's about monitoring -- looking for lice all the time, and if they're found, approaching control in a well planned and thorough way." WHEN TO LOOK FOR LICE Lice mostly spread from sheep to sheep. Bought-in stock, travelling mobs and stray sheep are key suspects. lAll mobs should be checked at least twice each year. lAny sheep seen rubbing or biting their flank should be checked straight away. Tufts of wool caught on fences, trees or other structures usually indicate that sheep are rubbing. However, sheep rub for a number of reasons (for example, grass seeds, fleece rot and itchmite), so it is essential to see live lice to confirm an infestation. FAST FACTS l Regular monitoring of mobs for lice and early detection when an infestation begins are key elements of any well planned lice control program. l Careful inspection of sheep before purchase or introduction to a property can help prevent new infestations. l All mobs should be checked at least twice each year. lPurchased sheep should be isolated, monitored and treated if necessary. lStray sheep and those from neighbouring farms should be checked carefully prior to return. HOW TO LOOK FOR LICE lLay the sheep on its side in a well lit position, part the wool and look for lice. Lice are small -- less than two millimetres in length with a broad reddish head; young lice have cream coloured bodies whereas adults have red-brown stripes across their abdomen. lIf you need glasses to read a telephone book you will also need them to see lice. A magnifying glass might also help. lMake 10 long parts in the wool on the sides from neck, to shoulder, to mid-side, then flank. Parts should be at least 10cm long. Check at least 20 wool parts on any rubbed sheep. lMost lice are found near the skin. However, they move away from the skin and up into the wool when the fleece is shaded, for example when sheep are in close contact with other sheep. This is how they spread. lIn sheep with long wool, lice are most common along the sheep's side and sometimes on the back. After shearing, lice tend to be found under the neck and on lower flanks. lTurn the sheep over and inspect the other side. lThe more sheep you inspect, the more chance you have of finding lice if they are present. lOnce you have found one live louse you can stop. There will be many more lice that you can't find and all sheep should be treated after the next shearing. Once infection is identified, there are a number of treatment options available. Woolgrowers are urged to consult a products list available via LiceBoss (www. wool.com/LiceBoss) or in the FlyBoss Tools section of FlyBoss (www.flyboss.org.au) to identify effective treatment options. Woolgrowers should also refer to the LiceSense manual to help them manage lice, which is available at www.wool.com/externalparasites More information: http://www.wool.com/LiceBoss To look for lice, use good light and put your glasses on!