Fleece rot in sheep

What is fleece rot?

Fleece rot is a skin disease of sheep that occurs in high rainfall conditions. It results in a reduction in wool quality through damage to follicles and fibres, and stained wool that is unscourable. Fleece rot in sheep also increases the risk of flystrike on the body.

Fleece rot is the result of bacterial infection (most commonly Pseudomonas aeruginosa) on the skin and in the fleece of sheep that results in dermatitis and wool damage. Whilst some sheep can be more susceptible, fleece rot is not infectious. Fleece rot does not spread from one sheep to another.

When to watch for it

Fleece rot often develops following prolonged wetting of the fleece and skin, usually after 5–7 days. 

Prolonged rain can also lead to conditions such as dermo and flystrike.

Clinical signs

Know what to look for with fleece rot in sheep:

• The wool near the skin becomes crusted and matted
• Matted fleece forms in bands of wool fibre parallel to the skin
• Often staining of the fleece in bands, commonly green, yellow, brown, grey
• Sheep may be irritated and bite at wool

What’s the difference between fleece rot and lumpy wool?

It’s important to tell these two conditions apart, as their causes and treatments differ.

How to manage

Some sheep are more susceptible to fleece rot, so it is advised to select directly for fleece rot resistance. Susceptible sheep include:

• Those that have poor conformation along their backline, such as having a dip between or behind the shoulder blades where the fleece cannot dry out
• Sheep with a fleece type that lets the water in and dries out slowly

Observe weaner sheep closely from 4–6 month wool during wet times.

How to treat

There is no effective treatment available for fleece rot. The condition usually resolves spontaneously once the wool and skin dry out.

Once resolved at the skin level, as the wool grows it moves away from the skin but the fleece will remain stained until removed at shearing.

Avoid the use of antibiotics in mildly affected sheep as this will delay the immune respose.

How to prevent

Timing of shearing can help prevent fleece rot:

• Shearing lambs at less than five months of age can result in a higher incidence of fleece rot compared to if the first shearing is delayed until approximately 12–15 months of age
• Shear immediately before the start of the rainy season, as a short fleece dries quickly and rarely becomes affected by fleece rot
• Older sheep require at least three months after shearing for their fleece staple structure to form an effective barrier to rain.