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bacterial disease Cow Transmissible to humans

Ruminant listeriosis

Listeriosis is a bacterial infection of ruminants that most often affects the brain. The animal always turns in circles on the same side, keeps its head tilted and presents paralysis on one side of the face: this very particular appearance...

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Zoonosis Prognosis FAQ Sources Affected species

What is it?

The responsible bacteria is present everywhere in the environment, but it multiplies especially in poorly preserved silage: poorly packed silos, poorly closed, soiled with earth, or whose edges are moldy. This is why cases typically occur in winter and early spring, a few weeks after the opening of a poor quality silo.

It exists in three main forms in ruminants: the nervous form, the most visible; abortion; and a generalized form which mainly affects young animals.

Key point

Zoonosis: raw milk and raw milk cheeses from affected animals present a real risk for humans, particularly for pregnant women, infants, the elderly and immunocompromised people. Any suspicion must be reported to the veterinarian, and abortions must be reported according to the instructions of the veterinary services.

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:

Head tilted Staggering gait Paralysis Excessive salivation Difficulty swallowing Fever Reduction Loss of appetite Lying animal that does not get up Discharge from the eyes Fall in milk production Abortion Circling Visible third eyelid Stopped ruminating

Nervous form, most common in adult cattle.

The animal isolates itself, appears dazed, leans its head against a wall or barrier, and moves, always turning in the same direction.

The head is tilted to the side, one ear and one eyelid droop, the eye on the same side tears and the animal may no longer completely close this eyelid.

The lip and cheek on one side are paralyzed: the animal drools profusely, keeps food in the cheek and is no longer able to swallow properly.

Staggering gait, falls, then animal which lies down and never gets up again, often with pedaling movements.

Fever at the beginning, often moderate and quickly subsides, loss of appetite and drop in milk production.

Abortive form: abortions at the end of gestation, without nervous signs, sometimes several in the same herd, with retained placenta and metritis.

Generalized form: especially in calves and young lambs or kids, with profound depression, fever and rapid death.

Inflammation of one eye, with tearing and clouding, can be observed in silo-fed animals when silage particles contaminate the eye.

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 disease is caused by the bacteria Listeria monocytogenes.

This bacteria is very widespread in the environment: soil, plants, water, feces. Many animals carry it in their intestines without becoming ill.

It has an important characteristic: it continues to multiply in the cold, which explains winter cases and the risk of food kept in the refrigerator in humans.

It is destroyed by good acidification of the silage, but it proliferates as soon as the silo is poorly packed, poorly closed, soiled, or the acidification is insufficient. The edges, top of the silo and moldy areas are the most dangerous.

In the nervous form, the bacteria travels up to the brainstem via the nerves of the face, often from a small wound in the mouth: this is why the paralysis is on one side only.

Distribution of silage, particularly poor quality silage: poorly packed silo, pierced tarpaulin, irregular leading edge, moldy edges, harvested fodder too soiled with earth.

Fermented foods with insufficient acidification, or damaged wrapped bales.

Winter period and end of winter, when the silos have been open for several weeks.

Stress and drop in immunity: advanced gestation, calving, transport, sudden change of ration, deficiencies.

Damp and dirty litter, poorly maintained buildings.

Drinkers and feeders soiled with soil or fermented remains.

Transmission

In animals: mainly by ingestion of poorly preserved silage, food or water contaminated with soil.

By the contaminated environment: wet and dirty litter, dung, soiled soil.

From mother to fetus during gestation, which causes abortion.

Infected animals excrete the bacteria in dung, milk and uterine secretions after an abortion, which maintains contamination of the building.

In humans: mainly through food, in particular raw milk, raw milk cheeses and contaminated ready-to-eat products. Direct contact with sick animals or with abortion products may cause skin or eye damage.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

The veterinarian recognizes the nervous form by its very particular picture: damage to only one side of the face, head tilted, walking in a circle, difficulty swallowing.

It rules out other causes of nerve damage in cattle, including ear infections, deficiencies, poisoning and other infectious diseases, including certain regulated diseases.

Questioning the feed is essential: type of fodder, date the silo was opened, appearance of the edges, presence of mold.

In the event of an abortion, samples from the fetus, placenta and mother allow the bacteria to be identified in the laboratory. Any abortion should be reported to the veterinarian, as other serious illnesses should be looked for.

Always handle an aborted fetus and its placenta with gloves, then wash your hands thoroughly: these are very contaminating products.

Treatment

The nervous form is an emergency: the sooner treatment is started, the greater the chances of recovery.

Treatment is based on antibiotic therapy prescribed by the veterinarian, at high intensity and over a prolonged period, because the bacteria is lodged in the brain and difficult to reach. Penicillins and tetracyclines are part of the families used. The choice, doses and duration are the sole responsibility of the veterinarian.

An anti-inflammatory and supportive treatment are often combined.

Nursing care makes a big difference: animal placed calmly on thick bedding, turned regularly if it is lying down, watered and fed with food that is easy to swallow, at the level of its mouth. An animal that no longer swallows correctly risks going the wrong way: the veterinarian indicates how to feed and water it without danger.

Immediately remove suspect fodder from the ration, for the entire herd: this is as important as the treatment itself.

Milk from sick animals or those undergoing treatment should neither be consumed nor marketed.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Everything depends on the quality of the fermented fodder.

Harvest cleanly: sufficient cutting height to avoid picking up soil, clean windrows, avoid molehills and areas soiled with manure.

Pack the silo carefully, close it tightly and quickly, and protect it from rodents and birds.

Advance regularly on a clean attack front, without leaving forage exposed to the air for days.

Systematically eliminate moldy, hot, smelly or earthy parts, particularly on the edges and top of the silo: never distribute them to the animals, even mixed with the rest.

Do not distribute wraps with holes in the film.

Clean feeders and troughs of fermented remains, maintain dry and clean litter.

Isolate affected animals and handle aborted fetuses and placentas carefully.

There is no widely available vaccine; in some countries vaccines are used, with limited effectiveness. Prevention therefore begins first and foremost through eating habits.

Possible complications

Death of the animal, especially when treatment has been delayed.

Long-lasting nervous after-effects in survivors: head remaining slightly tilted, eyelid drooping, difficulty gripping food.

Mistaken food routes and inhalation pneumonia in animals that no longer swallow properly.

Retained placenta, metritis and infertility after abortion.

Eye damage which may leave a lasting opacity.

New cases in the herd as long as the affected forage remains distributed.

When to see a veterinarian

An animal runs in circles, leans its head against a wall or keeps its head tilted: call the veterinarian immediately.

An ear, an eyelid or a lip falls to one side, the animal drools and is no longer able to swallow.

An animal staggers, falls, or lies down and never gets up again.

Abortions occur in the herd: notify the veterinarian without delay, an investigation into the causes must be initiated.

Many animals show nervous signs in the weeks following the opening of a silo.

You have handled an abortion or placenta without gloves and you have a fever or flu-like symptoms: consult a doctor and report the contact, especially if you are pregnant.

Transmission to humans

Listeriosis is a disease transmissible to humans, and food is the main route.

The risk comes mainly from raw milk, raw milk cheeses, and more generally from ready-to-eat products kept cold, because this bacteria continues to multiply in the refrigerator.

Never consume milk from a sick cow or one undergoing treatment. Boil or pasteurize raw milk before consumption: this is the most effective measure on the farm.

Direct contact is a secondary but real route: handling an aborted fetus, a placenta or a sick animal can cause skin damage or conjunctivitis. Wear gloves, keep your hands away from your face, and wash your hands and forearms thoroughly afterward.

The people most exposed to serious forms are pregnant women, in whom the infection can cause abortion or damage to the newborn, the elderly, infants and people with weakened immunity. These people should not handle abortions or consume raw milk.

Any unexplained fever or flu syndrome after contact with animals or after consumption of raw milk warrants medical consultation, reporting exposure.

Prognosis

In the nervous form, the prognosis directly depends on the speed of treatment. Treated at the first signs, an adult bovine can recover, sometimes with minor after-effects. Treated late, or already in bed, he has little chance of surviving.

Calves and young ruminants affected by the generalized form rarely survive.

After an abortion, the cow usually recovers, but uterine complications and delayed reproduction are common.

At the herd level, removing the forage in question stops the appearance of new cases: this is the most decisive measure.

Frequently asked questions

Why do we talk about “silage disease”?

Because the bacteria proliferates in poorly preserved fermented fodder: poorly packed silo, pierced tarpaulin, moldy edges, fodder harvested with soil. On the contrary, well-made and well-acidified silage is a safe food.

Can an affected cow infect others?

Direct transmission between cattle is marginal: other cases generally come from the same fodder. This is why the first measure is to immediately remove suspect forage from the ration of the entire herd.

Can I consume milk from a cow with listeriosis?

No, under no circumstances, nor sell it. This bacteria is dangerous for humans, especially pregnant women. Generally, boil or pasteurize raw milk before consumption.

My pet's head is tilted: is it necessarily listeriosis?

No, an ear infection, deficiency, poisoning or other infectious diseases can give similar signs. Only the veterinarian can make the difference, and he must be called quickly because the treatment is all the more effective the early it is.