Home › Animalia › Animal health › Animal diseases › Botulism
Botulism
Botulism is not an ordinary infection: the animal does not become infected, it swallows an already manufactured poison. This poison is produced by bacteria which grows in decomposing matter in the absence of air. The source is almost always...
What is it?
Botulism is not an ordinary infection: the animal does not become infected, it swallows an already manufactured poison. This poison is produced by bacteria which grows in decomposing matter in the absence of air.
The source is almost always a corpse: a rodent, a bird, a dead cat caught in a bale of fodder or silage, or a dead animal that has fallen into a watering hole. The poison then diffuses into the fodder or into the water around the corpse.
Once swallowed, it blocks muscle control. The animal weakens, can no longer swallow, then can no longer get up, and ends up no longer breathing, while remaining perfectly conscious.
Key point
Herd emergency. When faced with several paralyzed animals without fever, immediately remove the feed and water distributed and call the veterinarian: every hour saved protects animals that have not yet been exposed.
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:
Progressive weakness, which most often begins with the hindquarters: the animal drags its legs, staggers, walks as if it were drunk.
He stays behind the crowd, then lies down and never gets up again, while he stays awake and follows with his gaze.
Difficulty swallowing: food and water come out through the mouth or nose, abundant salivation, soft tongue which sometimes hangs out.
Slack jaw, drooping eyelids, limp tail.
Appetite often preserved at the beginning: the animal seeks to eat but cannot, which is very evocative.
No fever: the temperature remains normal, which distinguishes botulism from infectious diseases.
Breathing becomes more and more difficult as the respiratory muscles are affected, then death.
Several animals from the same batch are affected within a short period of time, generally a few hours to a few days after the same meal.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Ingestion of poison already formed in contaminated food or water.
Corpse of rodent, bird, cat or other animal collected with fodder during harvest and enclosed in a bale or silo.
Poorly preserved silage, insufficiently acidic or poorly packed, which allows bacteria to develop.
Water point soiled by a corpse: pond, open cistern, uncovered drinking trough.
Waste, poultry manure or poultry litter spread or accessible to animals.
Chewing on bones and remains of corpses by animals lacking minerals: this abnormal behavior exposes people directly to poison.
Distribution of silage or wrapped bales that have been poorly preserved, ripped open or stored for a long time.
Harvesting plots where rodents abound.
Open water points, ponds, cisterns accessible to wild animals.
Proximity to a poultry farm or spreading of poultry manure.
Mineral deficiency causing animals to chew bones or carcasses.
Corpses left on site or buried superficially near pastures.
Transmission
There is no contagion from one animal to another: a sick sheep does not contaminate its neighbors, the sheepfold, or the breeder.
The only route is the ingestion of the poison present in contaminated food or water.
This is why the number of cases follows the distribution: all animals that ate in the same place are exposed, those from another batch are not.
Identifying the offending food or water bowl and removing it immediately protects animals that are not yet affected. This is the most useful measure of all care.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian suspects the disease when several paralyzed animals, without fever, remain conscious.
It rules out other causes of paralysis or recumbency: hypocalcemia, listeriosis, tetanus, spinal cord damage, poisoning, deficiencies.
Detecting the poison in the laboratory is difficult and often negative, including in real cases: a negative result does not exclude the disease.
The investigation is therefore as important as the analyses: it is necessary to examine the fodder distributed, open suspicious bales, inspect silos and water points in search of a corpse.
Keep samples of the fodder and water distributed the previous days: they are valuable for the investigation.
The declaration and the action to be taken must be discussed with the veterinarian, particularly for the destination of the animals and products.
Treatment
There is no treatment capable of undoing the paralysis once it has taken hold: the poison has already blocked muscle control, and recovery depends on the slow regeneration of nerve endings.
The absolute priority is to immediately remove the source for all other animals: stop the distribution of suspect fodder, seal off the water trough, remove the corpse.
Affected animals receive supportive care decided by the veterinarian: calming down on thick bedding, regular turning, watering and feeding adapted to an animal that swallows poorly, protection against bedsores.
Never force an animal that does not swallow to drink from a bottle: the liquid passes into the lungs.
A specific serum exists in certain countries; it only acts very early, before paralysis sets in, and its availability is limited. Its implementation is the responsibility of the veterinarian.
When the attack is advanced, the question of euthanasia must be raised with the veterinarian to avoid agony by asphyxiation.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention relies entirely on the quality of the fodder and the cleanliness of the water.
Inspect the bales and silage upon opening: an abnormal odor, a blackened area, the presence of a corpse or rodent remains requires the entire lot to be discarded, without hesitation.
Do not distribute silage that has been poorly preserved, poorly packed or has been ripped apart for several days.
Mow while leaving sufficient cutting height and limit rodent populations in plots and stocks.
Cover and clean water points, regularly check drinking troughs, prevent animals from accessing ponds and open cisterns.
Collect and dispose of any dead animals immediately, both on livestock and in pastures; never leave a carcass near grazing or watering areas.
Do not spread poultry manure on plots intended for grazing or mowing, and never allow animals to access them.
Correct mineral deficiencies with the veterinarian: a properly supplemented animal does not try to chew bones.
Vaccination
Vaccines against certain forms of botulism exist and are used in countries where the disease is common.
They only protect against the types of poison they contain: they in no way replace the quality of the fodder and the cleanliness of the water points.
Their availability varies depending on the country and periods. Only your veterinarian can tell if vaccination is indicated and accessible in your region, and for which animals.
Possible complications
Death from paralysis of the breathing muscles, which is the most common outcome in reported forms.
Pneumonia due to passage of food or liquid into the lungs in an animal that no longer swallows.
Bed sores and muscle lesions in animals lying down for a long time.
Serial losses in a batch until the source has been removed.
Slow and incomplete recovery in the rare animals that survive mild forms.
When to see a veterinarian
Several animals stagger or lie down at the same time without having a fever: call immediately.
An animal tries to eat but is unable to swallow, or water comes out of its nose.
Its tongue hangs out, its jaw is soft, its tail is inert.
He lies in bed, unable to get up, but remains awake and attentive.
You discover a dead rodent or bird in a bale of fodder or in a water trough: immediately remove the food or water and call, even if no animal is yet sick.
Prognosis
Dark as soon as paralysis sets in: the majority of affected animals die, even when treated.
Mild forms, in animals that have swallowed little poison, can recover slowly, over several weeks, with careful care.
At the herd level, everything depends on how quickly the source is identified and removed: animals that have not yet eaten the contaminated food can be completely spared.
Frequently asked questions
My sheep are paralyzed but do not have a fever: is this possible?
Yes, and this is precisely characteristic. Botulism is not an infection of the body but a poisoning: the temperature remains normal and the animal remains conscious even though it can no longer move. This is an important element to report to the veterinarian.
Is the neighboring herd at risk of being contaminated?
No, the disease is not transmitted from one animal to another. The risk only concerns animals that have consumed the same food or water. On the other hand, if the fodder comes from a shared lot, those who received it must be informed without delay.
Should I throw away the whole bale of fodder where I found a corpse?
Yes, and without hesitation. The poison diffuses into the fodder around the corpse and there is nothing to demarcate the contaminated area by eye. The saving of one bale is not worth the loss of a batch of animals.
Does cooking destroy the danger in meat?
Don't think like that. Meat and milk from a sick animal should not be consumed and the dead animal should be disposed of according to the rules. Ask your veterinarian what action to take rather than taking a risk for your family.
References
ANSES — Agence nationale de sécurité sanitaire (France)
EFSA — Autorité européenne de sécurité des aliments
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
AT A GLANCE
Need a veterinarian?
Find a practitioner near you on TunisieVet, with their specialities, hours and contact details.
Find a veterinarianCategories
This information is provided for educational purposes only and is not a substitute for a veterinary consultation. If you have any concerns about your animal's health, consult a veterinarian.
To discover
Related diseases and linked Animalia content.
Toxoplasmosis
Parasitic
Coccidiosis
Parasitic
Foot-and-mouth disease
Viral · Vaccine available
Brucellosis
Bacterial · Vaccine available