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Coenurosis
Coenurosis, which breeders call whirling disease, is caused by the larval form of a dog tapeworm which lodges in the sheep's brain. The larva forms a fluid-filled sac that slowly grows and compresses the brain. Depending on where it settles...
What is it?
Coenurosis, which breeders call whirling disease, is caused by the larval form of a dog tapeworm which lodges in the sheep's brain.
The larva forms a fluid-filled sac that slowly grows and compresses the brain. Depending on where it settles, the animal always turns to the same side, tilts its head, loses sight in one eye or ends up no longer getting up.
It is a disease entirely linked to the presence of dogs around the herd: without an infested dog, there is no coenurosis.
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:
At the beginning, a few weeks after contamination, certain animals present a discreet phase: depression, animal which isolates itself, sometimes fever. In massive infestations, deaths may occur at this stage.
Then comes a long period without anything visible, which can last for months.
The typical signs then appear and slowly worsen: the animal turns in circles, always in the same direction, head tilted to the side.
He walks staggeringly, stumbles over obstacles, leans against a wall and pushes.
He often loses sight in one eye, on the side opposite the pocket.
He moves away from the herd, no longer follows, loses weight because he can no longer graze normally.
At an advanced stage: convulsions, paralysis, animal lying down and never getting up again.
In young people, you can sometimes feel a softening of the skull bone under your fingers, next to the pocket.
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 culprit is not a sheep worm but a tapeworm that lives in the dog's intestine.
The dog becomes infested by eating the head, brains or carcass of a sheep carrying the parasitic pocket, for example slaughter waste or a dead animal left in the field.
Once an adult in the dog's intestine, the tapeworm releases eggs in its feces.
Sheep swallow these eggs along with contaminated grass or water. The embryos pass into the blood, reach the brain and slowly form the sac there.
The cycle can therefore only be accomplished by passing alternately through the dog and the sheep: this is exactly the same logic as for the tapeworm responsible for the hydatid cyst, a much more serious parasite since it affects humans.
Presence of non-wormed dogs around the flock or in the sheepfold.
Habit of giving dogs heads, offal or remains of sheep slaughter.
Carcasses of dead animals left accessible to dogs and stray dogs.
Family slaughter without proper waste disposal, informal killings.
Route areas frequented by stray dogs.
Young animals, from a few months to two years old, which are the most affected.
Transmission
A sick sheep does not contaminate its peers, nor the breeder.
Contamination occurs only by swallowing the eggs present in the excrement of an infested dog, deposited on pastures, around sheepfolds, water points and places where fodder is distributed.
The herding dogs, farm dogs and stray dogs that roam around the kills and carcass dumps maintain the chain.
The eggs survive a long time in the external environment and disperse with rain and wind.
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 complete nervous examination: direction of rotation, position of the head, vision in each eye, reactions and gait. These elements often indicate the area of the brain concerned, therefore the probable location of the pocket.
He palpates the skull looking for a softened area in young animals.
He rules out other causes of nervous disorders in sheep, which are numerous and similar: deficiencies, poisoning, brain abscesses, infectious diseases, other parasites. Some are urgent and can be treated, hence the importance of not becoming dizzy at the mere sight of an animal spinning.
Examination of the brain after death confirms the diagnosis and, above all, alerts you to the presence of the cycle on the farm: the dogs must then be taken care of without delay.
Treatment
No antiparasitic given to sheep reliably destroys an already established pocket in the brain.
When the pocket is single, superficial and well located, a veterinarian can surgically remove it. The intervention requires equipment and experience; the results are good when the animal is still in good condition and the location is suitable.
When the pocket is deep, multiple, or the animal is already lying down and thin, surgery is not possible and euthanasia avoids long agony.
Whatever happens, the head and carcass of an affected animal must never be given to dogs: this is how the cycle starts again for the following years. Waste must be destroyed or disposed of according to the rules in force.
The real response to a case of coenurosis is not the treatment of the sick animal: it is the deworming of the dogs and the management of slaughter waste on the farm, with the veterinarian.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Never give raw sheep or goat heads, brains, offal or carcasses to dogs, regardless of the appearance of the animal.
Quickly collect dead animals from pasture and have them disposed of according to regulations, rather than leaving them accessible.
Regularly deworm herding and farm dogs with a product active on tapeworms, prescribed by the veterinarian, and collect their excrement around buildings when possible.
Limit the presence of stray dogs around sheepfolds, water points and slaughtering places.
Control family slaughter: waste must be destroyed, never thrown to dogs.
These same actions also protect the family from a much more serious disease, hydatid cyst, transmitted to humans by the eggs of another dog tapeworm: this is the best reason not to neglect deworming dogs.
Wash your hands after touching a dog and before eating, and wash garden vegetables if dogs have access to them.
Possible complications
Progressive and inevitable worsening in the absence of intervention: the animal stops eating, loses weight and dies.
Falls, injuries and drowning in water sources among animals who can no longer see or find their way.
Permanent loss of vision.
Animal lying down, bedsores and painful end of life.
Maintenance of the cycle on the farm if dogs and slaughter waste are not managed, with new cases each year.
When to see a veterinarian
An animal always turns in circles on the same side or keeps its head tilted.
It pushes against walls or stumbles into obstacles.
He no longer seems to see to one side.
He moves away from the herd, no longer follows, loses weight.
He has convulsions or remains lying down without getting up: consult without delay, other serious but treatable nervous diseases give the same signs.
Several young animals present with nervous disorders a few weeks apart: the entire herd and the management of the dogs must be examined.
Prognosis
Without intervention, the evolution always takes place towards the death of the animal.
Surgery carried out by a veterinarian on a well-localized pocket, in an animal still in good condition, gives good results and often allows spectacular recovery.
At the herd level, the prognosis is excellent if the breeder breaks the cycle: dewormed dogs and slaughter waste never given to the dogs make the disease disappear from the farm.
Frequently asked questions
Is whirling disease contagious between sheep?
No. An affected sheep does not contaminate any other sheep. Contamination only comes from the excrement of a dog carrying the tapeworm: it is therefore on the dog that we must act.
Can I give the head of a slaughtered sheep to my dogs?
No, never. This is exactly the action that maintains the disease: the dog swallows the parasitic bag, develops the tapeworm and then sows eggs on the pastures. The same gesture also transmits the tapeworm responsible for the hydatid cyst in humans.
What does this have to do with hydatid cyst?
The mechanism is identical: a dog tapeworm, eggs in its excrement, a larva which settles in an organ. The difference is that, for the hydatid cyst, the larva can develop in humans, with serious consequences. Deworming your dogs and never giving them raw offal therefore protects both the herd and the family.
Can we treat a spinning sheep with a dewormer?
No. No dewormer given to sheep reliably eliminates a pocket in the brain. Only surgery, when the pocket is well located and the animal is still in good condition, can save it. The veterinarian will judge the possibility of intervention.
My pet is spinning in circles: is it necessarily dizzy?
No. Several sheep diseases give very similar nervous signs, some of which can be treated well if we intervene quickly. A veterinary examination is essential before concluding.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
OMS — Organisation mondiale de la santé
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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