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"New-gen" louse treatment is pure venom to lice

By Dr Claire Hunt, Bayer Animal Health

September 2019

The sheep body louse, Bovicola ovis, causes significant financial losses to the Australian sheep industry annually; estimated losses are between $81 million1 and $123 million2 depending on the total sheep numbers in any one year. Use of a new generation lousicide with an effective treatment plan can ensure any resistant lice are cleaned up for good.

Lice can cause a reduction in harvested wool weight due to rubbing and wool lost on fences; the remaining wool has less value due to damage and discolouration. Financial losses are therefore based on reduced wool cut as well as prevention methods and costs associated with treating lousy sheep.

Early detection of a louse infestation is important to help reduce the widespread use of insecticides and minimise associated production losses. It is in every producer’s interest to regularly check their sheep for signs of lice. All mobs should be checked at least twice yearly; checking can be done at the same time as yarding for other management procedures. If sheep show signs of lice they should be checked as a matter of urgency. Early stage lousy sheep will frequently be itchy even with low numbers of lice; the consequent scratching and rubbing will result in fleece derangement.

To maximise the chances of seeing lice it is important to select sheep exhibiting signs of lice

infestation i.e. deranged fleece and/or actively scratching and check 20+ partings per sheep. If one louse is found that is sufficient to isolate the mob and declare them lousy. A management program should then be decided on to contain or treat the infestation.

Biosecurity remains a pivotal non-chemical control method for sheep lice. A robust biosecurity plan is critical to minimising the risk of lousy sheep entering a farm and causing an infestation. By far the most common reason for a new louse infestation is a stray lousy sheep getting in to a mob, usually undetected. By the time the stray sheep is detected it is likely to have had sufficient time to contact others in the mob and spread lice. Other common causes of lice spread include broken fence lines, introduction of new sheep, incomplete mustering and untreated lambs at foot.

Lice management programs are primarily designed around an integrated strategy approach to prevent infestations. Treatment options should be planned and implemented when required, including judicious use of effective chemical lousicides. Having access to highly efficacious lousicide products is an important piece of the puzzle in controlling sheep body lice.

Bayer’s product, Viper® is a next generation sheep lousicide containing thiacloprid, an active not found in any other lousicide product on the market. Thiacloprid is a high potency neonicotinoid insecticide that has been shown in extensive trials on Australian sheep to be 100% effective at killing lice when applied to shorn sheep up to 7 days off shears in a convenient backline formulation.

Thiacloprid acts on the nervous system of lice resulting in their paralysis and death. Bayer laboratory studies show it is six times more potent to lice than the widely used imidacloprid3. Using a lousicide with residual activity offers peace of mind to producers that juvenile lice hatching from eggs will also be killed. Viper offers four weeks residual activity against lice when applied within 24 hours of shearing.

As with any chemical use on farm, it is important to formulate a rotation plan of active groups to help minimise resistance development and maintain the efficacy of products on the market.


1. Priority list of endemic diseases for the red meat industries (2015) Lane, J., Jubb, T., Shephard, R., Webb-Ware, J. and Fordyce, G. Project B.AHE.0010 Report, Meat and Livestock Australia.

2. Assessing the economic cost of endemic disease on the profitability of Australian beef cattle and sheep producers (2006) Sackett, D., Holmes, P., Abbott, K., Jephcott, S. and Barber, M. Project AHW.087 Report, Meat and Livestock Australia.

3.  Registration trial data on file

This is a paid ParaBoss-approved advertorial that supports LiceBoss recommendations.

LiceBoss does not advocate specific products or brands. Other proprietary products with the same active ingredients and formulation will also be suitable for this issue.