What is Body Lice?

Sheep body lice (Bovicola ovis) are responsible for most lice infestations of sheep and cost Australian sheep producers more than $120 million a year. While no official statistics are available on the occurrence of sheep lice in the Australian sheep flock, anecdotal evidence supports that the occurrence is high, and that many sheep producers will have sheep lice issues in some years.

The body louse is a small insect around 1-2mm in length. Young lice (nymphs) are cream coloured with a red-brown head, while adult lice have reddish-brown stripes across their body. Lice feed on dead skin of sheep, lanolin, skin bacteria and sweat gland secretions. Lice do not suck blood or eat the wool fibers, that cause thickening of skin. Body lice are a common problem in Victorian sheep flocks and cause significant economic loss as a result of:

Decreased wool quality and quantity
Treatment costs (both chemicals and labour)
Limited market opportunities (it is an offence to sell lousy sheep in Victorian saleyards)

How Lice Are Spread

Commonly lice move from infested sheep to clean sheep during direct contact. Lice move from the tip of the fleece and will usually spread during:

Joining (introduction through rams)
In yards or races
During transport
In sheep camps
Introduction of new stock to a property (either purchased in or strays)

Transmission of lice through contact with infested wool on fences is unlikely, however in sheltered areas lice may survive in greasy wool for a couple of days.

Lice are sensitive to temperature and humidity and most will die soon after being removed from sheep. Research work has shown that some lice can survive for up to a month in favourable conditions.

Diagnosis

It can take around 5-6 months for newly infested sheep to develop signs of a lice infestation. The first sign of lice infestation is usually rubbing sheep (i.e. on fences). Once sheep are at the “rubbing” stage, it is often a sign that lice are in high numbers and treatment should occur at the first opportunity.

Figure 1. Sheep infested with lice (Source: DPIRD)

Checking For Lice

It is difficult to see lice in small numbers on sheep. The best time to see lice is immediately prior to shearing.

Check all mobs at least twice a year (i.e. during crutching and before shearing) and check any sheep with rubbed or pulled wool
In bright sunlight, check for lice by parting the wool in a number of places where sheep have rubbed or where the wool is matted. You will see the lice move away from the light.
Make a number of parts (about 10) on each side starting at the neck and working along the side of the sheep to thigh
On shorn sheep, protected areas around the folds on the neck are the preferred areas. In woolly sheep, the mid-sides will generally hold the greatest numbers

Wool damage is usually only obvious once there is at least three months’ growth of wool and significant lice numbers.

Treatment

Effective treatment of all sheep in the flock is necessary to fully eradicate lice. Lousy sheep that have been treated may not show signs of infestation for up to nine months after treatment. Usually this is due to the treatment not eradicating all lice.

When selecting a treatment product, consider selecting a treatment for ewes as well. Depending on the product, it can take between 2 and 18 weeks after treatment for lice to die. If lambs are born during this period, they can become infested and re-infest ewes.

The best time to treat sheep for lice is soon after shearing, using a plunge dip. This allows the best chance of eradication and also minimises residue in wool (remembering wool processors will not tolerate chemical residues).

Opportunities to eliminate lice are “off-shears” (0-24 hours after shearing) or in short wool (1-42 days after shearing). Use of long wool backliners should only be considered as a control tool to limit further wool damage before shearing, but be aware of the wool harvest intervals. If you are going to the expense of treating lice, ensure you don’t leave any sheep behind when mustering and that you treat all sheep.

Backliners

	When To Use	Advantages	Disadvantages	Notes
Off-Shears Backline	Immediately after shearing <24 hours unless stated otherwise	Less labour intensive	Slow to kill High chemical cost Effectiveness reduced in sheep not cleanly shorn	If used properly some can achieve eradication
Long-Wool Backline	6 weeks – 10 months wool	Less labour intensive Low maintenance No discharge of used dipwash	Slow to kill High chemical cost Potential for high chemical residue in wool	Apply evenly from poll to tail
Jetting	Used as a control method until lice can be eradicated at shearing		Control only

Dips

	When To Use	Advantages	Disadvantages
Plunge Dip	3 weeks off-shears	Very effective if used correctly Contractors available who have a mobile plunging system	Expensive to set up own facilities Labour intensive Bacterial infection can be spread
Shower Dip	2-3 weeks	Less labour intensive	Generally less effective Expensive to set up own facilities Difficult to achieve necessary saturation for maximum effectiveness More chemical exposure for operator Method not regularly used

Always read the label and consider residues and withholding periods when selecting and using chemicals for control and eradication of lice. Remember, selling lousy sheep through saleyards is illegal.

Prevention

There are a number of steps that can be carried out on farm to prevent lice infestation. Carrying out best practice management and biosecurity strategies is the best way to prevent introducing lice to your flock as well as other sheep diseases.

Ensure boundary fences, timber plantations, creek crossings, etc. are maintained and are “sheep-proof” to minimise strays and interaction of animals between fences. Pay particular attention to timber or tree plantations where stray sheep can remain undetected and intermingle with your sheep
Consider introducing buffer zones along boundary fences. This will allow you to deal with stray sheep before they are introduced to your own sheep
Work with your neighbours to improve fences and discuss strategies to prevent and manage lice problems in your area. Neighbours should have a “no stray” policy. Should a neighbour find one of your sheep on their property, ask them not to put it back over the fence but contact you for collection. This means you can quarantine stray animals before re-introducing them to your flock
Always inspect sheep before purchasing new stock and ask for a National Sheep Health Statement
Isolate new sheep on arrival until the next shearing to minimise the chance of introducing lice (or other diseases) to your flock. Keeping records of stock movement around the farm can be effective in managing the risk of spreading lice throughout your flock
Shearers can transfer (adult) lice inadvertently on their moccasins for up to 10 days after they have worked on properties with heavy lice infestations. There is a low probability of this occurring and should not be your main focus of prevention. However microwaving moccasins for 5 minutes can minimise the risk of transfer.

Best practice management and biosecurity strategies are the best way to preventing introducing lice to your stock.

Further Resources

Lice boss is an effective online tool that can be used to help aid producers in constructing a lice control management plan specific to their region. For more information follow the link here.

Meat & Livestock Australia – Lice

NSW Department of Primary Industries – Sheep Lice

Farm Trader – Lice Treatment

Click here to download the PDF version.

For further information, please contact the VFF Livestock Group on 1300 882 833 or by email [email protected]

Disclaimer: All care is taken in the preparation of the information and published materials produced by the Victorian Farmers Federation (VFF) including but not limited to errors, defects or omissions in the information provided. VFF does not make any representations or give any warranties about the accuracy, reliability, completeness, or suitability for any particular purpose in the preparation of the information and published materials. This publication is intended for general information purposes only and does not constitute financial, legal, investment, production, or marketing advice. To the maximum extent permitted by law, the VFF and all persons acting on behalf of the VFF in preparing documents, are excluded from all and any liability for any loss or damage of any kind arising in relation to this publication including any reliance on the information contained herein.