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Bacterial meningoencephalitis of sheep
We speak of meningoencephalitis when the infection affects both the brain itself and the coverings surrounding it. In adult sheep as in Antenna sheep, it manifests itself as a feverish, depressed animal which loses control of its movements...
What is it?
We speak of meningoencephalitis when the infection affects both the brain itself and the coverings surrounding it. In adult sheep as in Antenna sheep, it manifests itself as a feverish, depressed animal which loses control of its movements and its vision within a few hours to a few days.
The bacteria reach the brain through the blood, from a source located elsewhere in the body: breast, uterus after giving birth, lung, infected foot, wound, abscess. They can also progress from neighboring structures in the head, such as the sinuses or a tooth root.
Unlike brain abscess, which grows slowly on one side, meningoencephalitis strikes on both sides at once and sets in quickly: the animal is feverish, hypersensitive, stiff, and its condition deteriorates from hour to hour.
Key point
Fever and nervous disorders in a sheep constitute an emergency of the same hour. Many of the possible illnesses are very treatable if you intervene right away, and not at all the next day.
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:
Fever, often high at the start of the episode.
Deep depression, animal which remains motionless, head lowered, no longer follows the herd, refuses to eat and ruminate.
Stiffness of the neck, tense back, mechanical gait.
Hypersensitivity to noise, light and touch: the animal startles or stiffens when approached.
Tremors, muscle contractions, abnormal head movements.
Staggering gait, animal stumbling, getting stuck, falling.
Loss of vision, often in both eyes, with animals bumping into everything.
Head tilted, spinning, pressing the head against the walls.
Convulsions, tense limbs, pedaling movements in a lying animal.
Animal lying on its side, which no longer gets up, within a few hours to a few days.
Often, a source of infection elsewhere on the body: hot udder, smelly vulvar discharge after giving birth, infected foot, wound, cough.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Various bacteria can reach the brain and its coverings in sheep.
They most often come from an infectious source elsewhere in the body: infection of the uterus after giving birth or retained placenta, severe mastitis, pneumonia, infected foot, wound, abscess, infection of the navel in young people.
They can also progress step by step from the sinuses, the inner ear, an abscessed tooth root or a deep wound on the head.
Listeriosis is the most classic bacterial cause in sheep and deserves to be known to every breeder: it is favored by the distribution of poor quality or poorly preserved silage, and often gives a unilateral picture with paralysis on one side of the face.
A weakened, poorly nourished animal, at the end of gestation or at the beginning of lactation, is less resistant to bacteria that would normally have been contained.
Births in poor hygienic conditions, retained placenta, uterine infections.
Severe mastitis, pneumonia, infected feet, neglected wounds, chronic abscesses.
Distribution of poorly preserved, earthy or moldy fermented foods.
Dirty, damp, poorly ventilated, high density sheepfold.
Weakened animals: end of pregnancy, beginning of lactation, significant parasitism, undernutrition.
Deficiencies in trace elements and vitamins which reduce defenses.
Interventions on animals carried out without hygiene: injections, buckles, clipping, trimming.
Transmission
It is not a disease contagious from sheep to sheep through simple proximity: each animal becomes infected from its own home or environment.
But several close cases in the same herd almost always indicate a common cause: poor quality fermented food, an unsanitary sheepfold, a series of births in poor hygienic conditions. It is this common cause that we must look for.
The bacteria involved in some of these attacks, in particular listeriosis, can present a risk to humans in very specific situations; the sheet dedicated to listeriosis details these precautions. In all cases, washing your hands after handling a sick animal, an abortion or a placenta is a basic rule that cannot be discussed.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian takes the temperature, performs a complete nervous examination and examines the entire body in search of the source of origin: udder, uterus, feet, lungs, wounds.
He notes whether the signs are symmetrical, which indicates meningoencephalitis, or on one side, which suggests an abscess or listeriosis.
A blood test highlights the infection and assesses the general condition.
Samples from the source of origin, when it is identified, help guide the choice of antibiotic.
An analysis of the fluid surrounding the brain is possible depending on the means available and confirms the diagnosis.
The veterinarian rules out other causes of nervous disorders in adult sheep, which are numerous and misleading: listeriosis, polioencephalomalacia, coenurosis, brain abscess, enterotoxemia, tetanus, botulism, hypocalcemia, pregnancy toxemia, poisoning by lead, salt or plants. Many of them are treated very well when we intervene early, which prevents letting them spend the night.
Examining a dead animal is valuable when several cases occur: it identifies the cause and helps protect the rest of the herd.
Treatment
This is an emergency: treatment must be started without waiting for the results of the tests, on the veterinarian's decision.
It is based on an antibiotic capable of reaching the brain, which not all molecules do, administered by a suitable route and for a sufficient duration. An antibiotic effective on the same bacteria elsewhere in the body may be completely useless here if it does not cross the brain barrier: this is why the prescription cannot be copied from one disease to another.
An anti-inflammatory is often combined to limit brain swelling.
Supportive care is decisive: animal isolated in a quiet place, in the dark if possible, on thick bedding, turned regularly if lying down, water and food within immediate reach, rehydration if necessary.
A lying animal must be changed sides several times a day to avoid recumbency complications, and its stomach must be monitored, because a ruminant lying on the same side for a long time can become bloated.
Treatment must be continued until the end of the term, even after a marked improvement: relapses after early cessation are frequent and serious.
The original focus must be treated in parallel, otherwise the infection will start again.
Withdrawal times for meat and milk products used must be requested from the veterinarian and strictly observed.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Take care of the hygiene of farrowing: clean pens, fresh bedding, clean hands and equipment during interventions, rapid treatment of retained placenta and abnormal discharge.
Treat any source of infection immediately: mastitis, infected foot, wound, abscess, pneumonia. It is by leaving them lying around that we give the bacteria the opportunity to reach the brain.
Avoid distributing poorly stored, earthy or moldy fermented foods, and remove suspect parts of a silo.
Maintain a clean, dry and well-ventilated barn, avoid overdensity.
Ensure a correct diet and good mineral and vitamin status, particularly at the end of gestation.
Use clean equipment for all procedures and change needles between animals.
Call the veterinarian at the first nervous signs, at any time: this is the only factor over which the breeder really has control.
Possible complications
Death within a few hours to a few days in severe forms.
Permanent nervous after-effects in survivors: blindness, tilted head, abnormal gait, animal which no longer eats alone.
Relapse after stopping treatment too early.
Complications linked to prolonged immobility: bedsores, bloat, false swallowing pneumonia in an animal which no longer swallows correctly.
Abortion in a pregnant ewe.
Weight loss and reformation of survivors.
When to see a veterinarian
A sheep has a fever and at the same time presents nervous disorders: call immediately, whatever the time.
He is stiff, jumps at noise or touch, trembles.
He staggers, bumps into things, can no longer see.
He keeps his head tilted or pushes against a wall.
He lies on his side, limbs outstretched, or convulses.
He has just given birth and has a smelly discharge with deep depression.
Several animals in the herd show nervous signs: look for a common cause with the veterinarian, particularly in the area of fermented foods.
Prognosis
The prognosis depends above all on the delay: treatment started in the first hours, before the animal is laid down, leaves a real chance of recovery.
An animal already lying down, blind or convulsing has a poor prognosis, and survivors often have permanent after-effects.
At the herd level, the prognosis is good as long as the common cause is identified and corrected.
Frequently asked questions
How do you know if it's a brain infection or another nerve disease?
We cannot know this alone: a good dozen diseases give a very similar nervous picture in sheep. Fever points to an infectious cause, but it is not always present. The important thing is to call the veterinarian right away, because many of these illnesses are very treatable within the first few hours.
My pet has been lying down for two days, is it still worth treating?
This should be discussed honestly with the veterinarian. An animal that has been lying down for a long time, blind or convulsing, has a poor prognosis and is likely to suffer for a long time. The veterinarian will assess whether there remains a reasonable chance or whether euthanasia is the most respectful decision.
Can silage really make my sheep brain sick?
Yes, when it is poorly stored, earthy or moldy. This is a well-known mode of appearance of listeriosis in small ruminants, which is the subject of its own fact sheet. Removing suspicious parts of a silo and not distributing a questionable fermented food is a very concrete prevention measure.
Can I catch something from caring for an affected sheep?
Brain infections are not transmitted by simple contact. Certain bacteria involved, on the other hand, deserve very specific precautions, particularly when handling aborts and placentas. Wash your hands systematically, wear gloves during obstetric procedures, and ask your veterinarian for advice.
References
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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