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Lung abscesses
A lung abscess is a pocket of pus trapped in the tissue of the lung. The body was able to contain the infection by surrounding it with a thick wall, but it was unable to eliminate it. This wall is precisely what makes the situation difficul...
What is it?
A lung abscess is a pocket of pus trapped in the tissue of the lung. The body was able to contain the infection by surrounding it with a thick wall, but it was unable to eliminate it.
This wall is precisely what makes the situation difficult: it protects the bacteria from antibiotics, which do not reach inside the pocket. This is why an animal with an abscess seems to get better during treatment, then relapses shortly after stopping.
Abscesses are almost never a primary illness: they are the consequence of something else. Pneumonia that is poorly treated or treated for too short a time, inhalation of liquid, an infection of the navel in lambs, an infected wound, or the internal form of caseous lymphadenitis, this abscess disease well known to breeders in the Maghreb.
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:
Slow and steady weight loss in an animal that nevertheless continues to eat, at least initially. This is often the only sign for a long time.
Intermittent cough, sometimes oily, which may disappear for several days then return.
Shortness of breath on exertion, animal which stays behind the herd, which is out of breath on a hill or after a short run.
Variable fever, often moderate, which comes and goes: a normal temperature on a given day does not rule out anything.
Periodic loss of appetite, dull and brittle wool, animal losing its condition despite a good ration.
Thick discharge, sometimes purulent, more marked when the abscess communicates with a bronchus.
Unpleasant breath, even downright foul, when putrid bacteria are involved.
In lambs, growth stops abruptly and the animal remains small compared to its contemporaries.
Typical relapses: the animal gets better under treatment, then deteriorates again a few days or weeks after stopping.
In the event of rupture of the abscess in the chest cavity, sudden worsening with pain, refusal to move and respiratory distress.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Untreated pneumonia, treated too late or treated for too short a time: infectious sites that have not been sterilized become organized into pockets of pus. It is the most common and preventable cause.
Inhalation of liquid or food, particularly after poorly done drenching or too rapid bottle-feeding: bacteria from the mouth introduced into the lung form localized abscesses, often smelly.
An infection of the navel in the newborn lamb: the bacteria pass into the blood and settle in the lung, joints or liver. A lamb that has had omphalitis may develop remote abscesses.
The internal form of caseous lymphadenitis: this disease, very present in sheep and goat herds in the Maghreb, is not limited to abscesses visible under the skin. It also affects the deep lymph nodes and the lung, and then produces sheep who lose weight inexorably without any explanation being found.
The spread through the blood of an infection from elsewhere: mastitis, metritis, complicated foot rot, infected shearing or castration wound.
Foreign bodies or penetrating chest injuries, more rare.
History of pneumonia in the group, especially when treatment was discontinued upon improvement.
History of difficult drenching, bottle-feeding, or administration of oil by mouth.
Lambs with navel infection or polyarthritis.
Herds affected by caseous lymphadenitis, with abscesses visible under the skin in several animals.
Shearing equipment, needles and castration instruments not disinfected between animals.
Aged animals or animals in poor condition, very productive sheep, deficient animals.
Overcrowded, poorly ventilated and dusty sheepfolds, which breed respiratory diseases.
Lack of follow-up after an episode of pneumonia: animals which have not completely recovered are not identified.
Transmission
The abscess itself is not transmitted from one animal to another: it is an individual complication. On the other hand, the infections that cause them circulate. Pneumonia microbes pass from animal to animal through air and contact. Caseous lymphadenitis is spread very easily through pus from an open abscess, which contaminates shearing equipment, feeders, walls and floors, and through shearing, castration and buckling wounds. A single abscess punctured in the wrong place permanently contaminates a sheepfold. Breeding conditions which favor pneumonia, overloading and poor ventilation therefore indirectly favor Lung abscesses.
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 abscesses when an animal is slowly losing weight, coughing intermittently and relapsing after each treatment.
He auscultates the thorax: the noises can be discreet, because a well-encapsulated abscess does not always make noise. Normal auscultation therefore does not rule out the diagnosis.
Blood tests typically show long-lasting inflammation, with prolonged elevated markers. This is an important element of orientation.
A chest ultrasound, when accessible, allows abscesses located on the periphery of the lung to be visualized; an x-ray provides additional information.
In a herd affected by caseous lymphadenitis, specific blood tests and examination of superficial lymph nodes help to situate the problem on a group level.
Examining a dead animal or observing the lungs at the slaughterhouse is very instructive: pockets of pus are visible, and their discovery should lead to a review of the management of pneumonia and lymphadenitis on the farm.
The veterinarian rules out other causes of chronic weight loss in sheep, which are numerous: internal parasites, ovine pulmonary adenomatosis, maedi-visna, tooth problems, deficiencies, insufficient ration.
Treatment
Treatment is based on antibiotics prescribed by the veterinarian, chosen for their ability to reach the lung tissue, and administered over a long period of time. This is where most of the failures occur: a short treatment does not sterilize a pocket of pus, it numbs it.
No duration or dose should be decided without the veterinarian, and treatment should never be stopped at the mere sight of improvement.
An anti-inflammatory can be combined, on prescription, to improve comfort and appetite.
Supportive care is very important: quality food, animal isolated in a quiet, dry and well-ventilated room, clean watering, no transport or unnecessary handling.
Unlike an abscess under the skin, a lung abscess cannot be punctured: no intervention of this type is possible in the field.
You have to know how to recognize dead-end situations. An animal with multiple abscesses, very emaciated, which relapses each time treatment is stopped, will not recover. Continuing treatments is expensive, prolongs suffering and maintains resistance to antibiotics. Culling, decided with the veterinarian and respecting waiting times, is often the most reasonable course of action.
When caseous lymphadenitis is the cause in the herd, individual treatment makes practically no sense: it is a herd strategy that must be constructed, based on the identification, isolation of carriers and hygiene of interventions.
Waiting times for meat and milk, often long with prolonged treatments, must be requested and scrupulously respected.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Treat pneumonia completely, for the prescribed duration, even when the animal appears cured after two days. This is the most effective preventative measure against Lung abscesses. Have animals that have not fully recovered after a respiratory episode reviewed by the veterinarian, rather than leaving them lying around in the flock. Master the drenching and bottle-feeding technique: head in line with the neck, slow administration, immediate stop if the animal coughs. Never give oil from the bottle. Disinfect the navel of lambs at birth and take care of the hygiene of the lambing pen: many deep abscesses in lambs begin at the navel. Systematically disinfect shearing equipment, needles, curling pliers and castration instruments between animals. Identify and isolate animals with abscesses visible under the skin, never puncture them in the building or in the herd's living area, and have the pus removed according to the veterinarian's instructions. Mow suspicious animals last. Improve the sheepfold: less density, more ventilation, less dust and ammonia. Less pneumonia mechanically means fewer abscesses. Monitor the weight and body condition of animals: slow weight loss is seen much better by weighing or palpation than by eye. Use slaughterhouse returns: abscessed lungs reported regularly are a warning sign for the entire operation.
Possible complications
Rupture of the abscess in the chest cavity, leading to sudden and often fatal pleurisy.
Rupture in a bronchus, with flooding of the lung with pus, acute respiratory distress and profuse and fetid discharge.
Diffusion of bacteria through the blood to other organs: liver, kidneys, joints, brain.
Progressive weight loss to the point of exhaustion, with the animal ending up lying down.
Long-lasting decline in fertility and milk production in affected females.
Seizure of the carcass or parts of the carcass at the slaughterhouse, with direct economic loss.
Maintenance of the problem in the herd when caseous lymphadenitis is the cause and it is not managed collectively.
When to see a veterinarian
An animal slowly loses weight despite a correct diet and up-to-date deworming.
An animal has been coughing periodically for several weeks.
An animal gets better under treatment then deteriorates with each stop: report it, the strategy must change.
Foul breath or purulent discharge appears.
An animal becomes abnormally out of breath when exerted or systematically stays behind the herd.
An animal deteriorates suddenly, with pain and difficulty breathing: it is an emergency, the abscess may have ruptured.
Visible abscesses appear under the skin in several animals in the herd: the issue goes beyond the individual.
The slaughterhouse reports abscessed lungs: ask for advice even if the rest of the herd appears healthy.
Prognosis
The prognosis is guarded and depends on the number, size and age of the abscesses.
A single, recent abscess, in an animal still in good condition, can heal with long and well-conducted treatment.
Multiple or old abscesses, in an already emaciated animal, rarely heal. Relapses when treatment is stopped are the rule.
Animals affected by internal caseous lymphadenitis have a poor prognosis: the disease progresses slowly but surely.
At the scale of the herd, the prognosis is much better than at the scale of the individual: correctly treating pneumonia, taking care of the hygiene of the navel and clipping, and correcting the building will significantly reduce the problem.
Frequently asked questions
My sheep is constantly losing weight but she is eating: where can this come from?
Chronic weight loss in an eating sheep has several possible causes, including lung abscesses, internal parasites, tooth problems, pulmonary adenomatosis or maedi-visna. Only the veterinarian can sort it out, and the sooner he intervenes, the more options are open.
Why does my sheep relapse every time I stop the antibiotic?
Because an abscess is surrounded by a thick wall that the antibiotic does not penetrate well. The product puts the infection to rest without sterilizing it: as soon as it stops, it starts again. This is why these treatments take a long time, they must be decided by the veterinarian, and you must know how to give up when the animal no longer responds.
Can a lung abscess be punctured like an abscess under the skin?
No. A lung abscess is locked in the thorax: it is not accessible and no attempt of this type is possible. This is precisely what makes these abscesses so difficult to treat, compared to those of the skin.
My sheep have abscesses under their skin, is this related to the lungs?
It can be. Caseous lymphadenitis, the disease of abscesses, also affects the deep lymph nodes and the lung, and explains ewes which lose weight without any apparent cause. In this case, the problem is managed at the herd level: identification of carriers, strict hygiene of shearing and interventions, and never an abscess pierced in the building.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
ANSES — Agence nationale de sécurité sanitaire (France)
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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