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Ovine interdigital dermatitis
Interdigital dermatitis, which many breeders call scald or overheating, is an inflammation of the skin between the two hooves. It only affects the skin: the horn of the foot remains attached and intact. It is the leading cause of lameness i...
What is it?
Interdigital dermatitis, which many breeders call scald or overheating, is an inflammation of the skin between the two hooves. It only affects the skin: the horn of the foot remains attached and intact.
It is the leading cause of lameness in sheep flocks, particularly in grazing lambs after a wet period.
Its importance comes not from its individual gravity, which is weak, but from two things. First it hurts: a lame lamb grazes less and stops growing, and this loss of growth is paid for in the sale. Then, and above all, it prepares the ground for foot rot. The bacteria that causes scald is the same as that of footrot, in a less aggressive version; when a more virulent strain is present in the herd, it takes advantage of this already damaged skin to settle in and attack the horn.
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:
Rapid onset lameness, often on several animals from the same flock at the same time, in the days following rain or passing through wet pasture.
By spreading the two hooves: bright red skin, swollen, moist, sometimes bleached and macerated like skin left in water for too long.
Gray or whitish coating at the bottom of the space between the hooves, hairs absent or stuck to the area.
Slight unpleasant odor, much less marked than that of footrot.
Clear pain when pressure is applied to the area: the animal quickly withdraws the foot.
Hot foot when compared to the opposite side.
Animal which remains lying down, which moves little, which grazes on its knees in marked cases.
One or more feet affected, often the front ones.
Lambs which remain behind the flock, which stop growing, batches which are downgraded.
Essential point: the horn of the foot remains well attached, nothing comes off under the sole and on the walls. If it comes off, it's no longer scald.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
A bacteria living naturally on the skin and in the feet of sheep, the same family as that responsible for foot rot but in less aggressive strains, multiplies when the skin between the hooves remains moist and softened.
Another bacteria, very present in soils soiled by excrement, almost always accompanies the first and aggravates the inflammation.
Humidity is the absolute triggering factor: wet grass, dew, mud, soggy litter, trampled areas around water troughs and distribution points.
The heat associated with humidity accelerates the phenomenon, which explains the crises after the rains and on irrigated plots.
Stones, thatch and abrasive soils injure the skin between the hooves and open the door to bacteria.
A foot that has not been trimmed for a long time, with folded horn which retains mud, maintains humidity permanently.
Wet periods, rain, morning dew, irrigation, wintering in a sheepfold on soggy litter.
Overdensity, unrenewed litter, muddy watering areas.
Short and abrasive pastures, stubble, stony terrain.
Lambs and young animals, more sensitive than adults.
Untrimmed feet, long, folded horn that traps mud.
Repeated passages in the same restraining corridors.
Introduction of animals without quarantine or foot examination.
Presence of footrot in the herd, which aggravates the whole.
Transmission
Contamination occurs through the soil and through litter, where bacteria are brought by affected animals.
The forced passage areas are the hotspots for contamination: entrance to plots, surroundings of watering troughs, corridors, fodder distribution areas, where all the animals set foot in the same place.
Bacteria survive for a short time on dry, sunny soil, but much longer in a humid, soiled environment.
An animal introduced without quarantine can bring more aggressive strains, capable of tipping a herd from simple scald to take-all.
There is no risk for humans.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Examining the foot is essential: lameness cannot be judged from afar. The animal must be contained, the foot lifted, cleaned, and the two claws spread to see the skin on the bottom.
The veterinarian distinguishes scald from footrot by looking for detachment of the horn. This is the decisive gesture: he probes the edge of the sole and the heel to see if an instrument passes under the horn. If the horn holds, it is a scald; if it comes off, it's a stomp, and the strategy changes entirely.
It also rules out other causes of lameness: abscess of the foot, foreign body stuck between the hooves, contagious digital dermatitis which begins at the bead above the hoof, laminitis, arthritis, fracture.
He evaluates the number of animals affected in the lot: a massive and sudden attack after a rain points towards scald, a progressive attack which worsens despite treatment points towards something else.
A herd visit with examination of a sample of animals allows you to take stock of the situation before implementing a strategy.
The veterinarian can also train the breeder in correct trimming: poor trimming damages the foot and aggravates lameness.
Treatment
The first step is to get the animals out of the humidity: place them on a dry plot, or on clean and abundant bedding in a building. Without this, no treatment will work.
A local treatment, applied directly to the skin between the hooves after cleaning, is generally sufficient. The product and its instructions for use are indicated by the veterinarian; certain presentations to be sprayed fall under the prescription.
When many animals are affected, the foot bath treats the entire batch at once. The solution used, its concentration, the frequency of passages and the contact time are decided with the veterinarian: a preparation that is too concentrated burns the feet, too diluted it is of no use, and a dirty footbath itself becomes a source of contamination.
A decisive practical point: the animals must exit the footbath into a clean, dry area and stay there for a while. Passing them and then immediately throwing them back into the mud negates the entire benefit.
Gentle trimming, limited to what is necessary, removes the folded horn that retains the mud. You should not trim raw: aggressive trimming creates wounds and causes lameness.
General treatment, on prescription, is reserved for severe cases or those who do not respond, and should then have the diagnosis reconsidered.
Animals which continually relapse despite correct behavior must be examined again: it is often a case of foot rot or contagious digital dermatitis mistaken for scald.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Keep feet dry as much as possible: drain muddy areas, stone or concrete around water troughs and distribution points, move racks.
Mulch abundantly and renew the litter in buildings; Soggy litter alone causes lameness.
Avoid overdensity and prolonged parking in corridors.
Rotate plots and avoid very humid pastures during risky periods.
Examine the feet during each handling of the herd and treat the first lame ones immediately, rather than waiting until the entire flock is affected.
Quarantine any purchased animal, examine its feet and put it in a footbath before putting it in contact with the herd: this is how we avoid importing foot rot.
Organize footbath visits during risky periods, according to a plan established with the veterinarian.
Trim your feet at a reasonable pace and learn the correct movement: excessive trimming does more harm than good.
Separate and care for lame animals separately, so as not to contaminate the passage areas of the rest of the herd.
Vaccination
There is no vaccine specifically targeting interdigital dermatitis.
However, vaccines exist against footrot in certain countries, and can be discussed with the veterinarian in heavily affected herds: by reducing footrot pressure, they also reduce all lameness. Their availability and interest depend on the local situation.
Possible complications
Evolution towards footrot when aggressive strains are present in the herd: this is the most costly complication.
Loss of growth in lambs, which does not completely recover.
Loss of body condition of ewes, with consequences on fertility and lactation.
Animals that remain lying down become weak and become targets for flies.
Superinfection of lesions and abscesses of the foot.
Chronic lameness and early reforms.
Lambs which, no longer able to follow the flock, fall behind and die from accidents or predation.
When to see a veterinarian
Several animals in the same group begin to limp at the same time, especially after a wet period.
The lameness persists despite local care and passage on a dry plot.
The horn of the foot comes off or an instrument passes under it: it is no longer a scald, call the veterinarian.
A strong bad odor emanates from the foot.
Only one foot is very painful with swelling above the claw.
The lesions start at the labrum, just above the horn, and go down: this suggests another, more serious disease.
Lambs stop growing and stay lying down: lameness costs more than you think.
Prognosis
Excellent: treated and left dry, the animals heal quickly and without after-effects.
Relapses are common as long as wet conditions persist, but they do not leave lasting damage to the foot.
The prognosis only deteriorates if the disease develops into foot rot, which then involves a much longer herd struggle.
On a farm scale, cleaning up muddy areas produces spectacular and lasting results.
Frequently asked questions
How do you know if it's a scald or a footrot?
Checking to see if the horn comes off. In the scald, the skin between the claws is red and moist but the horn holds up well. In footrot, the horn separates from the flesh, you can pass an instrument under it, and the smell is frankly putrid. This difference governs the entire course of action: ask the veterinarian to show you the gesture once, you will know how to do it then.
Should I trim all their feet when my sheep are lame?
No, and this is a common error. Systematic and aggressive trimming creates sores, bleeds and causes new lameness. You must limit yourself to removing the folded horn which retains the mud. Treatment for scald involves first removing the animals from humidity and treating the skin.
My footbath doesn't do anything, why?
Several possible reasons: solution too diluted or, on the contrary, too concentrated, bath dirty and loaded with mud, contact time too short, or animals thrown directly into the mud when leaving. This last point is the most common: they must be left in a clean and dry area after passing. Have the protocol established by your veterinarian.
Does a limp really cost you money?
Much more than we imagine. An animal that is poorly grazed less and moves less: lambs stop growing, ewes lose condition, fertility and lactation suffer. The real cost of a batch of lame people is measured in unproduced kilos, well before the price of medicines.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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