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Enzootic pneumonia of lambs
Enzootic pneumonia of lambs is the most common and costly respiratory disease in sheep farming. “Enzootic” simply means that it is permanently established in the flock: it returns every year, on each flock of lambs, without the need for an...
What is it?
Enzootic pneumonia of lambs is the most common and costly respiratory disease in sheep farming. “Enzootic” simply means that it is permanently established in the flock: it returns every year, on each flock of lambs, without the need for an external introduction. It is not caused by a single microbe. Mycoplasmas, small bacteria which cling to the carpet of cilia of the trachea and bronchi, prepare the ground; respiratory viruses often come before them; then banal bacteria, already present in the noses of all animals, descend into the lung and cause inflammation there. None of this is enough to make a well-housed lamb sick. What triggers the disease is almost always the environment: overcrowded sheepfold, confined air, straw and fodder dust, the smell of ammonia that hits the throat, sudden temperature differences between day and night, mixture of animals of different ages and origins. Its reputation as a “not serious” disease is misleading. It rarely kills, but it permanently damages the lungs of some of the lambs, which will never reach the expected weight at the expected age. It’s a silent loss, spread across an entire band.
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:
A dry, short cough that comes back in fits. It goes completely unnoticed on animals at rest: the good reflex is to get the lot to get up and walk, then to listen. A batch that coughs as soon as it is taken out is an affected batch.
Breathing faster than it should be at rest, flanks beating, lambs panting after a few meters while their contemporaries do not run out of breath.
Discharge from the nose, at first clear and runny, then thicker and yellowish as bacteria take over.
Moderate fever, often transient, and sometimes completely absent: not finding a fever never rules out the diagnosis.
Lambs which stay behind, which eat less quickly at the feed, with a reduction in feed consumption of the flock for no apparent reason.
Stalling growth: size differences appear between lambs of the same age and from the same mother, and widen from week to week.
Dull, pitted wool, animals that appear “dry” and do not round out.
In the most marked forms, frank depression, difficulty breathing with half-open mouth, animal which isolates itself in a corner: this stage requires a call to the veterinarian, because pasteurellosis can graft on top and kill in a few hours.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Several agents act in cascade, and this is what makes the disease difficult to resolve with a single product.
Mycoplasmas, very widespread in herds, attach to the cilia which line the trachea and bronchi. These cilia form a conveyor belt which constantly brings dust and microbes towards the throat; once this carpet is paralyzed, the lung no longer cleans itself.
Respiratory viruses circulate in parallel and also damage the mucous membrane.
Ordinary bacteria, which all lambs already carry in their noses without being sick, take advantage of this degraded terrain to descend into the lung and create centers of inflammation there.
Ammonia plays a central and very underestimated role. It is released from wet, urine-laden bedding and chemically burns the respiratory mucosa. A simple rule of thumb: if, upon entering the sheepfold in the morning, the smell stings the eyes and nose at eye level, it permanently attacks the lambs who live thirty centimeters from the ground, where the gas is most concentrated.
The dust from fodder and straw, the mixing of animals of different origins, the stress of weaning, transport and allotments complete the picture.
Overcrowded sheepfold: this is the first factor, before all others.
Insufficient ventilation, stagnant air, building closed to “protect from the cold”. Lambs suffer much less from dry cold than from humid and confined air.
Damp litter and ammonia, mulching too far apart, cleaning too rarely.
Dust: dry and dusty fodder distributed above the heads of animals, straw stirred without precaution.
Significant temperature differences between day and night, cold air currents near the animals, which is common in winter in the sheepfolds of North-West Tunisia.
Mixture of lambs of different ages in the same room, staggered arrivals without cleaning between flocks.
Sudden weaning, transports, allocations, dietary changes which add up in the same week.
Lambs that have received poor colostrum at birth, or whose mothers are thin.
Deficiencies in trace elements, particularly selenium and copper, common in certain soils and which weaken the defenses.
Closed fattening with high density, period when the disease is most expressed.
Transmission
Transmission occurs from animal to animal through the air, in droplets emitted by coughing, sneezing and breathing, and through direct nose-to-nose contact.
Adult ewes, which show nothing, harbor and maintain these microbes: they transmit them to their lambs from the first weeks. This is why there are practically no herds free of the disease and why the disease reappears every year without the introduction of animals.
The closer the animals are and the more confined the air, the higher the dose of microbes inhaled: the density in the barn matters as much as the presence of the microbes themselves.
Purchases, fairs, groupings and the return of unsold animals accelerate the circulation of agents to whom the herd is not accustomed.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian begins by examining the building as well as the animals. The height of the air, the smell, the humidity of the litter, the density, the presence of drafts often tell him more than a sample.
He lifts and moves the lot to trigger coughing, then examines the thorax with a stethoscope on several animals, sick and healthy, in order to assess the proportion of the lot actually affected.
He takes the temperature of several lambs: a fever in several animals at the same time points to a bacterial complication which requires a rapid response.
Samples from the nose or deep in the respiratory tract, as well as blood tests, make it possible to identify the agents involved and guide the choice of treatment.
Examining a dead lamb or observing the lungs at the slaughterhouse is the most telling method: the affected areas, located at the front and bottom of the lung, are firm, dark red or grayish, clearly demarcated from healthy tissue. Relaying this information often changes the conduct of an entire workshop.
The veterinarian finally rules out other causes of sheep cough: ovine pasteurellosis, sudden and febrile, ovine pulmonary adenomatosis in adults, pulmonary parasites, and accidental inhalation of liquid after poorly performed drenching.
Treatment
Treatment is based on antibiotics, chosen and prescribed by the veterinarian depending on the bacteria involved. Some families act on mycoplasmas, others do not: this is precisely why a product taken at random from the cupboard gives disappointing results.
No dose, duration or rhythm should be decided on your own initiative. Treatment stopped as soon as the cough subsides is the first cause of relapse and transition to the chronic form, with abscesses which settle in the lung.
An anti-inflammatory is often combined, on prescription, to reduce fever and pain and get the lamb back to eating and drinking more quickly.
Treating an isolated animal is of little benefit when an entire flock is coughing: the veterinarian thinks on a flock scale and decides whether to treat just the affected animals or the entire group.
Treatment alone is never enough. If density, ventilation and bedding do not change, lambs will relapse as soon as antibiotics are stopped, and the farm enters a cycle of costly and increasingly less effective repeated treatments.
Supportive care is just as important: lighter lot, dry and clean corner, clean water at height, palatable food, non-dusty hay, cessation of handling and transport during convalescence.
The waiting periods for meat and milk, specific to each product, must be respected without exception. Have them clarified by the veterinarian before any slaughter, particularly when the lambs are intended for a nearby sale, such as that of Eid.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is primarily a question of building, not of medicine.
Reduce density. A less loaded lot coughs less, eats better and grows faster: this is the most profitable measure of all.
Ventilate without creating a draft on the animals. The air should enter high and exit high, sweeping the volume above the lambs. An open, dry building is better than a closed, damp building.
Monitor ammonia: mulch sufficiently, drain regularly, correct waterer leaks which soak the litter. The smell test upon entering in the morning, before the doors open, is a good free indicator.
Limit dust: distribute the fodder without shaking it over the animals, remove moldy bales, lightly moisten very dusty areas.
Run the strips completely empty when possible: empty, cure, clean, let dry, then put back a homogeneous strip. Avoid adding younger lambs to an existing flock.
Spread out the stressors: do not wean, vaccinate, transport and change the diet in the same week.
Take care of the colostrum at birth and the condition of the ewes at the end of gestation: a well-started lamb resists much better.
Quarantine purchased animals before mixing them with the herd.
Take stock with the veterinarian of trace element deficiencies and the possible benefit of vaccination against the bacteria responsible for serious forms, particularly in farms which lose lambs every year.
Vaccination
There is no vaccine that protects against all the agents of enzootic pneumonia, because several different microbes are involved at the same time.
On the other hand, vaccines exist against the bacteria responsible for the acute and fatal forms which often occur in this area, in particular pasteurellosis. On farms which regularly lose lambs at the time of weaning or fattening, the question deserves to be asked to the veterinarian, who will judge the interest of a protocol and its calendar on the ewes and the lambs.
No vaccine compensates for an overcrowded and poorly ventilated building: it complements breeding management, never in its place.
Possible complications
Transition to the chronic form: the lung remains damaged, the lamb coughs for weeks and never catches up with its growth delay.
Installation of abscesses in the lung, difficult to treat and often permanent.
Extension of the infection to the envelope of the lung, the pleura, with painful pleurisy and a significantly worse prognosis.
Transplantation of pasteurellosis on an already weakened lung, with sudden deaths among the lot.
Adhesion found at the slaughterhouse, leading to partial seizure of the carcass and devaluation.
Increased susceptibility of the entire flock to other diseases, in a context where the animals are already weakened.
When to see a veterinarian
Several lambs from the same flock cough when they are made to stand and walk.
A lamb breathes quickly at rest, with its sides flapping, or blows at the slightest effort.
A lamb is breathing with its mouth half open and its neck outstretched: it's an emergency, call immediately.
A thick or yellowish discharge appears in many animals.
The batch's feed consumption drops without changing the ration.
The lambs are no longer gaining weight and size gaps are widening in a homogeneous flock.
One or more lambs die suddenly after a few days of coughing: do not throw the animal away, notify the veterinarian, the lung examination guides the entire management of the flock.
The cough returns as soon as the treatment is stopped: it is the building that must be re-examined, not just the product.
Prognosis
Caught early and treated correctly, a lamb recovers well and resumes growth.
Forms that persist, poorly treated or stopped too quickly, leave permanent lesions: the animal survives but remains a poor fattener, more susceptible to all other diseases.
On a batch scale, the prognosis depends much more on the building than on the choice of antibiotic. Farms that correct density, ventilation and litter see the problem decline sustainably; those who treat without changing anything find the same situation with each band.
Frequently asked questions
My lambs are coughing but eating well: should we really be worried?
Yes. Cough is the visible sign of an already damaged lung, and the cost of the disease is paid mainly in lost growth, not in mortality. A batch that coughs at weaning will come out later and lighter. It is also an area on which pasteurellosis can take hold and kill in a few hours.
Should we close the sheepfold to protect the lambs from the cold?
This is the most common error. Lambs tolerate dry cold well if they have clean bedding and no direct draft on them. What they can't stand is the confined, humid, ammonia-laden air of a closed building. Better a ventilated and dry room than a sealed room.
Why does the cough come back as soon as I stop the antibiotic?
Two reasons most often combine: treatment stopped too early, as soon as there is visible improvement, and an unchanged environment which continually reinfects the animals. The product cannot correct an overload of sheep or ammonia-containing litter. Talk to the vet again about the duration of the treatment and look at the building at the same time.
How do I know if it's pneumonia or something else?
Only the veterinarian can decide, because several diseases cause coughing in sheep. A sudden attack with high fever and rapid death is more reminiscent of pasteurellosis; an adult who loses weight with fluid flowing from the nose when his head is lowered suggests pulmonary adenomatosis; a cough that follows shortly after a drenching suggests inhalation of liquid. The course of action is not the same in the three cases.
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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