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Dermatophilosis (cutaneous streptothricosis)
Dermatophilosis is a skin disease caused by a particular bacteria, capable of moving and germinating as soon as the skin is wet and damaged. It is the water disease that remains. A fleece soaked by repeated rains, a flock that never dries b...
What is it?
Dermatophilosis is a skin disease caused by a particular bacteria, capable of moving and germinating as soon as the skin is wet and damaged.
It is the water disease that remains. A fleece soaked by repeated rains, a flock that never dries between two downpours, an overflowing water trough, a damp sheepfold: wool soaked in water removes the natural barrier of the skin and the bacteria takes hold.
The result is very recognizable in the hand: the wool coalesces into hard, crusty clumps, as if cemented to the base of the rovings. This is what shearers call lumpy wool. The torn scab removes the wool and leaves a red, moist, bleeding and painful wound.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Hard, cemented masses of wool, which can be felt when passing over the back, spine, shoulders and sides, even before seeing anything.
By removing the strands: thick crusts, yellowish to brown, stuck to the base of the wool, often in small islands that come together.
Under the torn scab, a bright red, moist wound, which bleeds easily and is frankly painful: the animals shy away when the area is touched.
Typical locations: the back line and the spine, where the rain runs off, then the sides, face, ears and nose in young people.
In lambs, shape of the limbs: red, budding crusts above the hooves and on the pasterns, which cause lameness and sometimes refusal to walk.
Affected animals generally do not itch: this helps avoid confusion with scabies or lice. Here the skin hurts, it doesn't itch.
In extensive forms: depression, sometimes a little fever, decreased appetite, animal losing weight.
Fleece soiled, brittle and impossible to shear properly.
Some animals only have a few discreet scabs and heal on their own when dry weather returns.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The bacteria responsible lives in the crusts, which are its reservoir. In the presence of water, it releases mobile forms capable of reaching neighboring skin and germinating there.
Two conditions are necessary together, and this is the key to the disease: prolonged humidity, and skin with a broken barrier. A fleece wet for days is enough to soften the skin; thorns, thistles, rubbing, mowing wounds, insect and tick bites open the door.
This is why the disease breaks out after periods of repeated rain, in bushy plots, or in the weeks following mowing carried out in poor conditions.
Insects and ticks play a dual role: they create micro-wounds and transport the bacteria from one animal to another.
Animals that are weakened, deficient, young, or already suffering from another disease defend themselves less well and develop more extensive forms.
Periods of repeated rain and fog, wet seasons, animals that never dry out due to lack of shelter.
Absence of sheltered grazing areas and buildings to dry out.
Damp sheepfold, soggy litter, leaking roof, overflowing water troughs.
Long, dense fleece, which retains water in contact with the skin.
Bushy and thorny paths, which injure the skin.
Strong pressure from biting insects and ticks.
Mowing with dirty equipment, or in wet weather, or leaving cuts.
Young, thin, deficient animals, or those carrying internal parasites.
Mixture of animals of different origins and quarantine-free purchases.
Transmission
By direct contact between animals, especially when the fleece is wet.
By the crusts which fall and contaminate the litter, sleeping areas, feeders and equipment: they remain infectious for a long time once dry.
By biting insects and ticks, which carry the bacteria and open the skin.
By shearing equipment, combs and the hands of shearers, who spread the disease from one animal to another during the same working day.
By the introduction of a carrier animal, sometimes without visible lesion.
To humans, through skin contact with affected animals, their scabs or their wool: this point is detailed below.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian first relies on the very particular appearance of the lesions and the context: a series of humid days preceding the appearance of the scabs is a major element of orientation.
It rules out other sheep skin diseases, in particular scabies and lice – which cause itching, which is not the case here – and ringworm, whose lesions are more rounded and dry.
The diagnosis is confirmed in the laboratory, on a scab taken: microscopic examination reveals the bacteria in a characteristic form. It’s a simple test that avoids weeks of unnecessary treatment.
The veterinarian evaluates the extent in several animals in the group and the general condition of the herd, because widespread forms mainly affect weakened animals.
He looks for triggering factors on the farm: shelter, litter, roof, thorny plots, insect pressure, mowing conditions. Without this part, the treatment does not work.
Finally, it informs the breeder and his family of the risk of transmission to humans and the precautions to take.
Treatment
The first treatment is not medicine: it is to put the animals dry. As long as the fleece remains wet, the disease progresses despite everything applied. Shelter, a dry sheepfold, clean and abundant litter change the course of things.
Mild forms often heal on their own as soon as the animals dry out and the skin closes.
Extensive or painful forms require antibiotic treatment, with veterinary prescription only. The bacteria responds well when the treatment is implemented correctly, but the choice of product and management is up to the veterinarian.
The scabs can be softened and gently removed, after veterinary advice, to allow the skin to heal. It is a painful manipulation: it is done with caution, never by dry tearing.
All removed scabs must be picked up and disposed of, never left in the litter or on the floor: they remain contagious for a long time.
Affected animals separate from healthy animals as long as the lesions are active.
Treatment against biting insects and ticks is often useful at the same time, because they maintain the disease.
Weakened animals need sustained nutrition: the general condition determines healing as much as the antibiotic.
No dose or rhythm can be improvised, and home preparations applied to already raw skin aggravate the pain and lesions.
Withdrawal times for meat and milk apply and should be asked by the veterinarian.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Offer animals the opportunity to get dry: pasture shelters, accessible building during rainy periods. This is the most effective measure of all.
Maintain the sheepfold: waterproof roof, dry litter renewed regularly, correct ventilation, drinkers that do not overflow.
Avoid grazing very thorny and bushy plots during wet periods.
Control biting insects and ticks with the help of the veterinarian.
Take care of shearing conditions: clean and disinfected equipment between animals and especially between herds, shearing in dry weather, avoid cuts, mow healthy flocks before affected flocks.
Do not return freshly shorn animals to wet pasture whose skin is exposed and vulnerable.
Isolate affected animals, pick up and remove the scabs.
Quarantine and examine purchased animals.
Maintain good nutritional status and correct deficiencies: a healthy herd develops much lighter forms.
Possible complications
Extension of lesions to a large part of the body in weakened animals, with pain, emaciation and depression.
Fleece completely devalued: crusty wool is unusable and shearing becomes difficult and hurtful.
Permanently damaged skin and leather.
Persistent lameness in lambs affected by limbs, which graze less and fall behind.
Superinfections of wounds and attraction of flies during the hot season, with risk of myiasis.
Relapses with each rainy episode until the shelter and litter have been corrected.
Contamination of people handling animals, wool or scabs.
When to see a veterinarian
You feel hard, cemented clumps of wool when passing your hand over the back of your animals.
Thick crusts stuck to the base of the wool appear after a period of rain.
A torn scab leaves a red, moist, painful sore.
Lambs are lame with budding red scabs above their hooves.
Several animals in the group are affected at the same time.
An animal loses weight, is slaughtered or has a fever with extensive lesions: consult without delay.
Lesions appear in the weeks following mowing.
You or a loved one have pimples or scabs on the hands and forearms after handling animals: consult a doctor and let them know.
Transmission to humans
Dermatophilosis can be transmitted to humans. The people exposed are those who handle affected animals, their wool and their scabs: breeders, shepherds, shearers, and children who approach the animals.
In humans, it results in painful pimples, pustules and crusts, most often on the hands and forearms, at the points of contact. The lesions generally heal, but they warrant medical advice: consult a doctor, telling him that you are working with sheep affected by a skin disease, this information guides the diagnosis.
The risk increases when the skin of the hands is already damaged, cut or macerated by humidity: this is why working in the rain and mowing are particularly exposed moments.
The precautions are simple and effective: wear gloves when handling affected animals, their scabs and their wool; wash your hands and forearms thoroughly after work; protect and cover any cuts; change work clothes; keep children away from affected animals.
Wool from sick animals must be handled with care and reported, and shearing equipment cleaned and disinfected.
Prognosis
Mild forms heal well, often spontaneously, as soon as the animals are dry.
Extensive forms also recover with appropriate veterinary treatment and sheltering, but recovery takes time and the year's fleece is lost.
Lambs with limb injuries recover well, provided they are treated before lameness prevents them from grazing.
The prognosis is significantly worse in animals that are thin, deficient or carrying other diseases: in them, the lesions spread and drag.
At the herd level, everything depends on correcting the conditions: without shelter or dry bedding, the disease returns each rainy season despite treatment.
Frequently asked questions
Can I catch it from shearing or handling my sheep?
Yes, it is a disease that is transmitted to humans through contact with the skin, wool and scabs of affected animals. It causes painful pimples and scabs, especially on the hands and forearms. Wear gloves, cover your cuts, wash thoroughly after work, and seek medical attention if any lesions appear and report your work with animals.
My sheep have scabs but are not scratching, is it scabies?
The absence of itching is a good indicator that it is not scabies. In dermatophilosis, the skin hurts rather than itches, and the wool coalesces into hard clumps. The veterinarian easily confirms by examining a scab in the laboratory, and this avoids buying scabies treatment for nothing.
Should affected animals be sheared?
This should be discussed with the veterinarian. Shearing can help by clearing the skin, but it is painful on active lesions, it spreads the bacteria with the equipment, and a freshly shorn animal left in the rain is very vulnerable. If we mow, we mow the healthy flocks first, in dry weather, with disinfected equipment, and we bring the animals in dry afterwards.
Why does the disease come back to me every year?
Because the underlying cause is not bacteria but prolonged humidity. As long as the animals have nowhere to dry — no pasture shelter, soggy bedding, leaking roof — the skin remains softened and the disease returns with each rainy episode, regardless of the treatment used the previous year.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
CDC — Centers for Disease Control and Prevention
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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