Livestock health
Lumpy wool in sheep

Noel O'Dempsey, formerly of the Agency for Food and Fibre Sciences
Reviewed by Geoff Knights, Agency for Food and Fibre Sciences

Key points

• Outbreaks of lumpy wool may occur after yarding or confining wet sheep, during or immediately after wet weather, dipping or jetting.
• Let sheep straight out of draining pens and smaller yards. Do not confine them. This will reduce the likelihood of outbreaks.
• Affected sheep are difficult to shear and more susceptible to flystrike.
• The majority of sheep recover spontaneously.
• Separate affected sheep. Shear and dip them last to minimise the spread of infection.
• Shearing should be attempted on sheep if the skin is still crusted, however, stop if the skin is being cut.
• Sheep that cannot be shorn should be treated with antibiotics to enable clean shearing later.

Introduction

Lumpy wool (dermatophilosis or mycotic dermatitis) is an infectious disease of the skin of sheep and other animals. In sheep, scabs form and move outwards with the growth of the wool.

The organism Dermatophilus congolensis causes the disease, which is widespread in Queensland sheep areas. Cattle and horses can also carry it. The organism is probably present on your property even if you have not seen lumpy wool for years.

Signs

The fleece of affected sheep contains hard lumps, scabs or crusts that may be isolated or clumped in sheets of scab. In extreme cases, the whole skin surface may be covered by scab. The scabs are strongly attached to the skin at first, but later lift off the skin and grow out with the wool, often giving the sheep a ragged, or lumpy, appearance. There may also be lots of small scabs on the skin along the edge or upper surface of the ears, and also often on the lips, face, shanks and scrotum.

Most lesions heal within two or three weeks, a few take some months to heal and a small percentage remain active for years.

The disease can be distinguished from symptoms of lice infestations, itch mite and fleece rot by the presence of the crusts.

Spread

Lumpy wool is most likely to be transmitted in wet, crowded conditions. The spores carried on infected sheep germinate when wet and can be transmitted to non-infected sheep. Outbreaks occur most commonly when wet sheep are held together in yards after dipping, jetting or rain. There is also the possibility that very wet sheep camping close together on sheep camps will also spread the disease.

The spread of diseases and chances of outbreaks can be minimised by letting sheep out of the draining pens and smaller yards straight away, when sheep are being jetted or dipped for lice.

Ages affected

Lumpy wool is most common in younger sheep, especially weaners. Outbreaks are often seen after lamb marking if the sheep are wet by rain or jetting then held in the yards.

Older sheep can be severely affected if infected when stressed and if they have not previously been exposed to the disease, for example, after drought.

Effect on sheep and wool quality

The mild form of lumpy wool does not cause much discomfort to sheep or many deaths. However, it increases susceptibility to fly strike, and the growth and wool production of young lambs or more severely affected adult sheep can be retarded. Lambs severely affected may die shortly after birth.

The percentage of wool affected is generally low. Affected wool will be downgraded and discounted in price so should be removed from the main lines and placed in a separate line.

Management of affected flocks

In most sheep, the skin infection will cure itself in time and the hard lumps or crusts will lift away from the skin as the wool grows.

Fly and lice control

If flystrike is expected to be a problem, chemical protection is advisable as sheep affected by lumpy wool are more susceptible to flystrike. Draft affected sheep off into a separate group and ensure thorough penetrating insecticide coverage. Lice will cause a higher financial loss than lumpy wool; any necessary lice treatment can be performed at the same time.

Ewes and lambs should not be dipped together, particularly if the lambs are woolly. Spores carried by ewes will germinate when wet and be quickly transmitted to lambs. Jetting ewes or ewes with lambs to prevent flystrike will increase the chances of lambs getting lumpy wool. Skin damage in the lambs can be reduced by keeping the jetting pressure low. Adding zinc sulphate to the wash when jetting or dipping will minimise the spread of the organism.

Badly infected sheep should be hand jetted as thoroughly as possible rather than put through an automatic jetting race. Sheep should not be held in yards after dipping or jetting but let out as soon as possible after leaving the draining pens.

Individual sheep treatment

Check affected mobs of sheep eight weeks before shearing. In affected sheep where the skin infection persists, treatment with antibiotics will normally cause the scab to lift from the skin and allow sheep to be cleanly shorn.

Your veterinarian can advise you of the most appropriate choice of antibiotic. Set the dose rate according to the heaviest sheep in the mob. Antibiotics are an S4 drug and must be prescribed or supplied by a veterinarian and used under veterinary supervision. Consult your veterinary practitioner for dose rates applicable to the specific antibiotic prescribed.

A long period of wet weather after the injection could cause poor response to the treatment due to the enhanced conditions for spread of the organism and likelihood of re-infection.

Biological defleecing (BioclipÒ ) is a new method of fleece removal, where an injection is given to temporarily stop wool growth. A break in the wool fibres occur and nets secure the fleece on the sheep until they are ready for removal. This process is effective to remove fleeces from sheep with lumpy wool and can result in the disease being cleared up.

Shearing and dipping

At shearing, draft affected sheep off and shear and dip them last. Lumpy wool often occurs after shearing because of mechanical spread of the infection by the shears into shearing cuts and to areas of skin where the protective wax layer has been removed.

The incidence of infection increases in direct relationship to the number of days between shearing and dipping. The highest incidence occurs when sheep are dipped more than 40 days after shearing. As long fleece dries slowly, dip as soon as practicable after shearing. Sheep with encrustations still stuck to the skin will have to be treated with antibiotics and shorn six to eight weeks after the main shearing.

Dipping or spraying with zinc sulphate may help to prevent lumpy wool from spreading during dipping and infecting shearing cuts, but it will do little to control the disease in sheep already infected. Zinc sulphate can be used in two forms, check which form you use, as they require different mixing rates. The recommendations are:

• monohydrate form of zinc sulphate: 10 kg in each 1000 litres of dipping solution
• heptahydrate form of zinc sulphate: 15 kg in each 1000 litres of dipping solution.

Culling

Cull sheep in which lumpy wool persists or which fail to respond to treatment. This removes them as a source of infection.

The low heritability of the disease (0.1 to 0.15) does not allow much potential for breeding resistant sheep. There are no known characteristics of sheep or wool that can be used to identify susceptible sheep.

Further information

For further information contact the DPI Call Centre on 13 25 23 (Queensland residents) or (07) 3404 6999 (non-Queensland residents) between 8 am and 6 pm weekdays, or e-mail callweb@dpi.qld.gov.au.

This DPI Note is also published on the DPI's PrimeNotes CD-ROM.

Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.