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Lamb polyarthritis
Polyarthritis is an infection of the lamb's joints in the first weeks of life. Several joints are affected at the same time, hence its name. The bacteria do not arrive directly in the joint: they enter elsewhere, most often through the nave...
What is it?
Polyarthritis is an infection of the lamb's joints in the first weeks of life. Several joints are affected at the same time, hence its name.
The bacteria do not arrive directly in the joint: they enter elsewhere, most often through the navel, then travel in the blood and settle in the joints, which are a favorable environment in very young animals.
It is a painful disease. The lamb limps, then refuses to get up, no longer suckles and lets itself be left behind by the others.
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:
Lameness appearing in the first weeks of life, sometimes of one limb then of another.
Hot, swollen and painful joints, most often those of the knee, hock and fetlock; the lamb screams or tenses up when touched.
Lamb that remains lying down, gets up with difficulty, walks on its knees or drags a limb.
Fever, depression, bristling hair.
Refusal to suck, hollow stomach, very visible growth delay compared to other lambs of the same age.
In older forms, deformed, stiff joints and marked weight loss.
Sometimes, a still swollen or oozing navel that signals the front door.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Ordinary bacteria from the environment of the sheepfold pass through an open gateway in the newborn: the navel first and foremost, but also a castration or tail dock wound, or an injury to the mouth.
The germs most often involved are streptococci, staphylococci, colibacilli and, depending on the region, red mullet bacteria.
From there, they pass into the blood and lodge in the joints, sometimes also in the liver, lungs or lining of the heart.
A lamb that has not received enough colostrum does not have the antibodies to block this passage: this is the factor that comes up in almost all cases.
Navel not disinfected at birth, or disinfected too late.
Insufficient colostrum or taken late.
Damp and dirty litter, lambing pens reused without cleaning, overloaded sheepfold.
Lambing in mud or on bare ground.
Castration, rubber bands or tail docking carried out in poor hygienic conditions, or on lambs that are too young and weakened.
Lambs from multiple litters and lambs of small weight, more fragile.
Poorly cleaned feeding equipment in lambs fed milk replacer.
Transmission
The disease is not transmitted from one lamb to another by direct contact. What is transmitted is the contamination of the premises.
The bacteria live in soiled bedding, on the walls of lambing pens and on equipment. They infect every newborn born in this environment.
A series of cases in a batch therefore does not mean that the lambs are contaminating each other: it means that the birth environment is dirty and that the navels are not protected.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
See the vet early: an infected joint treated in the first days can heal, a joint damaged for two weeks never returns to normal.
The veterinarian examines each limb, palpates the joints, checks the navel and takes the temperature. He looks for other sources of infection (lungs, heart, eyes).
He can puncture a joint to analyze the fluid and identify the bacteria: this is what makes it possible to choose the most suitable treatment and to know what is circulating in the farm.
If there are several cases, he examines the entire batch and especially the lambing conditions: this is where the lasting solution lies.
It will rule out other causes of lameness in the young person, in particular a fracture, muscle damage or malformation.
Treatment
The treatment is based on antibiotic therapy prescribed by the veterinarian, continued for a sufficient period of time: stopping as soon as the lamb is better causes the infection to relapse and permanently damage the joint.
An anti-inflammatory is often combined to calm the pain and allow the lamb to get up and suckle. The pain, here, is not a detail: a lamb in pain does not suckle and becomes exhausted.
Comfort care is just as important: thick, dry bedding, lamb isolated in a pen with its mother, help with feeding if it can no longer do so alone.
An infected navel is treated at the same time, otherwise the source persists.
Very advanced cases, with deformed joints and weight loss, do not recover: the veterinarian can then advise euthanasia to avoid prolonged suffering without a solution.
No treatment should be repeated from one lamb to another without advice: the duration and choice of product are specific to each situation.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Disinfect the navel from birth, with a suitable veterinary product, and do it again if the cord remains wet. This is the most effective measure against this disease.
Ensure that each lamb takes its colostrum quickly, especially lambs in multiple litters.
Lamb on clean, dry and abundant litter; clean and re-mulch the pens between two sheep.
Avoid overloading the sheepfold during the lambing season.
Carry out castration and tail docking in good clean conditions, on healthy lambs, with disinfected equipment, and never on a lamb that is already sick.
Identify and isolate lame lambs early, to treat them before the joint is destroyed.
Empty and disinfect the sheepfold between two lambing seasons.
Possible complications
Permanent destruction of the cartilage and joint, with permanent stiffness and lameness.
Spread of the infection to other organs: lungs, liver, heart envelope, meninges, eyes.
Severe weight loss and irrecoverable growth retardation.
Prolonged suffering if treatment is delayed or interrupted.
Mortality, particularly in younger lambs or lambs already weakened by diarrhea.
When to see a veterinarian
Your lamb limps in its first weeks of life, even slightly.
One or more joints are swollen, hot, or screams when you touch them.
He remains lying down, refuses to get up or walks on his knees.
He is no longer suckling and is hollowing out compared to lambs of the same age.
His navel is swollen, hot or oozing.
Several lambs from the same batch are lame: have them all examined, this is a warning sign about lambing conditions.
Prognosis
Taken in the first few days, a properly treated lamb often recovers well, sometimes with residual stiffness.
Taken late, when the joints are already deformed, the prognosis is poor: the lamb will remain lame, sickly, and its suffering sometimes justifies a decision to euthanize.
At the herd level, the appearance of cases must be seen as a signal: it is by correcting the disinfection of the navel, colostrum and the cleanliness of the litter that the problem disappears.
Frequently asked questions
Why disinfect the navel when it dries on its own?
Because while it is wet, the cord is an open pipe to the lamb's blood. Disinfection makes it dry faster and closes that front door. This is the gesture that prevents both polyarthritis and omphalitis.
Just one lame lamb, should you really call the vet?
Yes, because time works against the joint. An infection caught early can be cured; the same infection two weeks later leaves a destroyed joint. And a first case often announces the following ones.
My lamb is lame but eating well: is it less serious?
This is a rather good sign, but it does not exempt you from an examination. Lameness in a very young lamb should always have the joints and navel checked.
Is polyarthritis contagious to other lambs?
Not directly from lamb to lamb. What is to blame is a contaminated birth environment, which infects each newborn separately. It is therefore the building that must be treated, not just the sick.
References
AVMA — American Veterinary Medical Association
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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