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Enzootic ataxia of the lamb
Enzootic ataxia is a nervous disease of the lamb caused by a lack of copper in the ewe during pregnancy. Copper is essential for the production of myelin, the insulating sheath that surrounds nerves and allows commands from the brain to rea...
What is it?
Enzootic ataxia is a nervous disease of the lamb caused by a lack of copper in the ewe during pregnancy.
Copper is essential for the production of myelin, the insulating sheath that surrounds nerves and allows commands from the brain to reach the limbs correctly. Without copper, this sheath is poorly constructed in the fetus. The orders come from the brain but arrive distorted: the lamb staggers, its hindquarters give way, it can no longer coordinate its movements.
Two forms exist. In the congenital form, the lamb is born already affected, unable to stand up. In the delayed form, the lamb is born normal, suckles, grows, then begins to drag its hindquarters after a few weeks to a few months.
Key point
Never supplement sheep with copper without analysis and without a prescription: sheep are the species which die most easily from excess copper, and poisoning strikes adult ewes which appear to be in good health.
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:
In the congenital form, visible from birth: lamb unable to stand up, which tips over on its hindquarters, or which gets up and falls down immediately.
Hind limbs stiff or on the contrary soft, which cross, which slip, hindquarters which oscillate from right to left with each step.
Head tremors, clumsy movements.
Lamb that crawls to move forward and cannot follow its mother, therefore does not suck properly and becomes cold.
In some cases, blindness or associated vision problems.
In the delayed form, in lambs from a few weeks to a few months: swaying gait, lamb which stumbles on a slope or when it is made to run, which stays behind the pack when moving, then which falls and never gets up again.
General condition preserved for a long time: the lamb eats, it is lively, only its hindquarters do not follow. It is this contrast that is striking.
Growth retardation and poor quality wool in affected animals.
Sometimes, in the same flock, several lambs affected to different degrees in the same year.
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 cause is a lack of available copper in the ewe during gestation, when the fetal nervous system is being built.
The lack can be a true deficiency, on soils and fodder poor in copper.
It can also be a so-called secondary deficiency, much more frequent and much more sneaky: copper is present in the ration but the animal cannot use it, because other elements block it. Excess molybdenum, sulfur, iron or zinc in forages, in soil ingested with grass or in water prevents copper absorption. A ration analysis showing a correct copper level therefore does not exclude the disease.
Certain breeds and certain lines are more sensitive than others, given the same diet.
Ewes carrying multiple lambs and those in poor body condition are more at risk.
The lesions form during fetal life and, for the delayed form, in the very first weeks of life: after which the process is complete.
Soils and fodder poor in copper, or on the contrary rich in elements which block its absorption, notably molybdenum and sulfur.
Pastures amended or located on certain particular lands, plots very rich in iron, water laden with iron or sulfur.
Absence of mineral supplementation of ewes during pregnancy, or supplement unsuitable for the local situation.
Sheep carrying multiple lambs.
Thin or poorly nourished ewes at the end of gestation.
Sensitive breeds and lines.
History of cases on the farm in previous years: the disease returns until the cause is identified.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian carries out a nervous examination which shows damage to the hindquarters with an animal that is otherwise lively and well conscious: this picture is very characteristic.
It is based on the context: several affected lambs, same region, same plots, history on the farm.
Blood tests on ewes and lambs, and especially liver tests carried out on a dead animal or at the slaughterhouse, make it possible to assess the copper status of the flock. The liver is the judge of the peace, because the blood can remain normal even though the reserves are empty.
Analysis of fodder, water and sometimes soil looks for elements that block copper absorption.
Examination of a dead lamb highlights the characteristic lesions of the nervous system and confirms the diagnosis: do not throw away an affected lamb without speaking to the veterinarian.
He rules out other causes of hindquarter weakness in young people: white muscle disease linked to selenium, spinal trauma, joint infection, meningitis, abscess in the spine. These distinctions are crucial because some of these diseases can be treated effectively.
Treatment
There is no treatment for lesions that are already present: the nerve sheath is not reconstituted.
A lamb that is already staggering will not get better because it is given copper. This illusion costs time and money, and poses a real danger of poisoning.
Slightly affected lambs can sometimes compensate as they grow and remain usable as slaughter animals, provided they are well fed, kept in a flat, obstacle-free enclosure, and supervised.
Lambs which cannot stand up, which do not suckle or which are injured by falling must be euthanized to avoid prolonged agony: the decision is made with the veterinarian.
The entire useful approach is geared towards the sheep still in gestation and towards the following campaign. Correcting the copper status of the flock, under veterinary supervision, can save unborn lambs.
Copper supplementation is never improvised in sheep: it is the domestic species most sensitive to copper poisoning, which accumulates silently in the liver for months then is suddenly released, killing adult ewes in apparently good health. Form, support, quantity and duration fall exclusively under veterinary prescription, after analysis.
Never use a mineral or feed intended for cattle or pigs on sheep: this is the classic cause of fatal copper poisoning in flocks.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Have the copper status of the herd assessed by the veterinarian when cases appear: blood tests, liver tests, forage and water analysis.
Correct the ewes' ration during pregnancy, with a mineral supplement adapted to sheep and the local situation, chosen and dosed by the veterinarian.
Never supplement with copper blindly, without analysis: the risk of poisoning is real and fatal.
Absolutely avoid minerals, foods and blocks formulated for cattle.
Monitor plots known to pose problems and adapt the management of pregnant ewes.
Feed ewes correctly at the end of gestation and prevent them from arriving thin at lambing.
Note the cases year after year: a disease that returns indicates an underlying cause that has not been corrected.
Avoid keeping descendants of the most affected lines for breeding when the problem persists despite a corrected ration.
Possible complications
Lambs that cannot suckle become cold and die within the first few days.
Falls, fractures, injuries and crushing in lambs that fall constantly.
Complete paralysis of the hindquarters and lying animal which no longer gets up.
Permanent growth retardation in survivors.
Significant and repeated losses from one campaign to another until the cause is corrected.
Risk of fatal poisoning of adult ewes if the farmer supplements with copper on his own initiative.
When to see a veterinarian
A newborn lamb cannot stand or tips onto its hindquarters.
A lamb a few weeks old drags, stumbles or lags behind the pack.
Several lambs from the same flock show an abnormal gait.
A lamb is lively and eats well but no longer coordinates its hindquarters.
Identical cases occurred last year: the mineral status of the herd must be analyzed before the next pregnancy.
You are considering supplementing with copper: definitely talk to your veterinarian before buying anything.
Prognosis
Unfavorable for affected lambs: the nerve damage is permanent and no treatment erases it.
Light forms can lead to the animal being slaughtered, but it will never make a breeder.
Excellent, however, at the herd level if the cause is identified and corrected before the next pregnancy: the disease disappears completely.
Prevention therefore takes place a season in advance, on the ewes, never on the lambs already born.
Frequently asked questions
My lamb is staggering from behind, can I give it copper to cure it?
No. Nerve damage has already occurred and cannot be repaired. Giving copper to this lamb will not put it back on its feet and exposes you, if you generalize the gesture to the flock, to fatal poisoning of the sheep. Copper is played during the mother's gestation, not after.
My forage analysis shows enough copper, how is this possible?
This is the most common and most confusing case. Copper may be present but rendered unusable by other elements in the ration or water, in particular molybdenum and sulfur. It is necessary to analyze the livers of animals, and not just the food, to know the reality of the reserves.
Is this the same as white muscle disease?
No, they are two separate illnesses. White muscle disease is linked to selenium and affects the muscles; enzootic ataxia is linked to copper and affects the nerves. They both produce a lamb that does not rise, but one responds to treatment and the other does not. Only the veterinarian can tell the difference.
Why are some lambs born normal and then start dragging later?
This is the delayed form of the disease. The nerve sheath continues to be built in the first weeks of life; if copper is lacking at this time, the signs appear late, often when the lamb is growing quickly. The mechanism is the same and so is the prognosis.
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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