Diagnosing lice & selecting treatments

LICE MANAGEMENT ON-FARM

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Lice in Australia

Sheep lice continue to be a major problem for the Australian sheep industry and a leading industry report has estimated they cost the Australian wool industry $107.6M each year1. Sheep lice infestations are one of the three most economically important health issues for sheep production within Australia and can:

Reduce greasy fleece weight by 0.2 – 1.1kg.
Reduce yield by 2.6% – 6%.
Decrease processing performance (reduced top yield and fibre length, increased carding and noil).

Body louse/Biting louse (Bovicola ovis)

The body louse or biting louse is the most prevalent and economically important species of louse found on sheep in Australia. The body louse feeds on skin debris and wool grease. The heaviest concentration of body lice is found along the sides of the sheep, from neck to flank. Body lice can also be found in the neck folds and shoulder areas. Sheep infested with the body louse will attempt to alleviate the irritation caused by their presence by scratching, rubbing, biting and pulling at their wool.
This results in:

Cotted (matted) fleeces.
Fleece discolouration (yellowing).
Fleece derangement.
Cockle (pelt defect which downgrades the value of the hide)

Lice life cycle

The time for completion of the louse life cycle from egg to adult lice will vary with environmental conditions.
The minimum time under ideal conditions is 34 – 36 days.
STEP 1: Each female louse lays eggs at a maximum rate of two eggs every three days. It is estimated that each female will lay 15 – 20 eggs in their lifetime.
STEP 2: The female louse attaches the eggs tightly to the wool fibre close to the skin.
STEP 3: Under ideal conditions, the eggs hatch in 10 days. From the egg emerges the first nymphal stage, which resembles the adult louse except it is smaller and colourless.
STEP 4: The louse moults again and grows bigger.
STEP 5: The louse moults a third and final time to become an adult louse and the process takes a total of 21 – 24 days. The adult female is ready to lay eggs 3 – 4 days later and the cycle continues.

Assess the need for treatment

For optimum lice control programs, detection of lice infestations is of critical importance – both to assess treatment and for early detection of reinfestation after eradication. All mobs should be inspected for lice at least twice a year. To inspect a mob for lice select 10 sheep, focus on sheep which show any sign of wool derangement.

Adult lice:

Are only 1 – 2 mm long.
Are only 1 – 2 mm long.
Are pale brown with dark bands across the body.
Live on the skin surface and along wool fibres, where they feed on the skin debris, wool grease and bacteria.
Are mainly found under the neck, especially in long wooled areas during first 3 months.
Become fairly evenly distributed in the fleece after 3 months.

For early infestations it must be remembered that the sensitivity of live sheep inspections for lice counts is low and monitoring for fleece derangement can be a relatively sensitive indicator of new infestations². Prevention can only be maintained by vigilance in ensuring the biosecurity of your property and constant monitoring of your flock.
When inspecting sheep for lice, most advisory recommendations are to treat all sheep if any lice
are detected³.

Figure 1: Lifecycle of the sheep body louse (Bovicola ovis)

Figure 2: Classification of the level of lice infestation based on the number of lice identified per parting

Figure 3: Examples of adult male and female sheep body lice, nymphs, and eggs.

Identifying Sheep Lice

Check before you treat

For gold standard lice control programs, detection of lice infestations is essential in determining IF or WHEN a lice treatment is required. All mobs should be inspected regularly when they are in the yards for routine husbandry activities. Mobs should at a minimum be inspected for lice at least twice a year, prior to lambing and prior to shearing.

Eradicating infestations

Due to the economic and welfare impacts of sheep lice within a flock, there is a focus on eradication. Unfortunately, industry feedback shows 70% of properties will fail to eradicate lice in a single lice treatment. Failure to eradicate can come from many sources, not treating 100% of sheep 100% correctly, split shearing, lambs at foot at treatment and biosecurity failures.
Due to the difficulties inherent in lice control when committing to a lice eradication program you must commit to:

Making changes within flock management and biosecurity.
A focus on accurate treatment.
More than one full flock treatment.
Close monitoring of mobs for lice.

Preventing infestations

Almost all lice infestations are introduced by lousy sheep coming into contact with uninfected sheep. This can be from:

Bought in or agisted sheep.
Sheep missed at muster and not treated for lice.
Strays coming onto a property.
Sheep straying from the property then coming back lousy.

Prevention can only be maintained by vigilance in ensuring the biosecurity of your property and constant monitoring of your flock. Industry often describes a three-year lice eradication plan. This allows three successive short wool lice treatments at shearing to work towards lice eradication. It also gives properties time to ensure that their biosecurity and quarantine processes are in place to reduce the risk of lice re-introduction after eradication is achieved. With the introduction of Flexolt there is the potential to condense a 3-year lice eradication program into a 12 to 18-month program. Flexolt allows for the possibility of two to three full flock treatments within a 12 to 18-month period, thus allowing eradication to be achieved quicker and minimising the impact of lice within the flock.

LICE MANAGEMENT PLANS

With the development of Flexolt, the only product which when applied correctly will be fully effective against lice in any length of wool. Producers are able to untie effective lice control away from shearing and only treat when a lice infestation is detected or at a point in the farm management calendar that is better suited due to sheep numbers, labour availability and the weather.

5 POINT LICE MANAGEMENT PLAN GUIDELINES

1. Treat all sheep at the one time.

All sheep must be treated at the same time. This includes lambs, rams, killers, ewes, wethers, and shedding sheep. If ewes have lambs at foot at treatment both ewes and lambs must be treated. If treating sheep pre-lambing ensure the selected product is applied early enough (follow label instructions) to allow all lice to die before lambing commences, or live lice can persist and infest lambs.
Flexolt gives you the option to treat all sheep at the same time if split-shearing occurs on farm.

2. Sheep are weighed to ensure accurate dosing.

Determine accurate body weights using scales. Dose to the heaviest animal in each group (ewes, lambs, weaners, wethers & rams). Incorrect dosing can have a significant impact on the efficacy of treatments. If weigh Scales are not used an accurate assessment of body weight is required.

3. Correct application of lice control products.

Follow label instructions on the correct application of products i.e. placement of backliners. If using backliners or dips, ensure all sheep are cleanly shorn. Poorly shorn sheep or sheep with cotted wool or dermo can reduce the efficacy of backliners and dip. The efficacy of Flexolt is not affected by poorly shorn sheep or cotted wool. Use the correct applicator for the product being used. Ensure all applicators are serviced and calibrated before treatment and regularly during use. During treatment ensure that each sheep is clearly identified as being treated. For Flexolt this means using a crayon, marker, or spray to identify treated sheep while working. One missed sheep can mean the failure of a lice eradication program.

4. Do not mix treated and untreated sheep.

Some lice products claim a period of protection against reinfestation. Despite these claims it is unwise to rely on chemical treatments to protect sheep from becoming infested. It is best practice to manage mobs so that treated and untreated sheep do not contact each other.

5. Quarantine and biosecurity.

A good biosecurity plan must assume that introduced sheep are infested with lice regardless of their history or whether there are no lice or signs of lice.
Ensure fencing is stock proof. This includes boundary and internal fencing. Stray sheep and sheep straying between mobs present a high risk for lice introduction and spread.
All brought in or agisted sheep should be treated and quarantined for lice.
Understand all introductions present a risk for introducing lice, this includes rams. Rams should be treated and quarantined for lice on introduction.
Remember a new lice infestation may take 3-6 months before signs of lice are evident. If stock are not treated for lice on introduction, they must be quarantined long enough for an infestation to become evident, or until all sheep on the property are being treated for lice.

Preventing infestations & reinfestation
Prevention can only be maintained by vigilance in ensuring the biosecurity of your property and constant monitoring of your flock. Almost all lice infestations are introduced by lousy sheep coming into contact with uninfected sheep.
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