Pneumonia in Horses
Pneumonia is inflammation and infection within the lungs. It can range from a relatively localised problem to a serious illness affecting a horse's ability to breathe and supply its body with oxygen.
Unlike a simple cough or mild airway irritation, pneumonia can make a horse systemically unwell. Early veterinary assessment is therefore important.
At a glance
Pneumonia affects: The lungs and lower respiratory tract
You may notice: Fever, coughing, nasal discharge, faster or more difficult breathing, lethargy, reduced appetite and poor performance
Common causes include: Bacterial or viral infection, inhalation of material into the lungs, complications following another respiratory infection, and circumstances that allow infection to establish deep within the lungs
Veterinary assessment: Recommended promptly if pneumonia is suspected
Important: A horse struggling to breathe, showing marked distress or rapidly deteriorating requires urgent veterinary attention.
What is pneumonia?
A horse's lungs contain an enormous network of very small airways and air sacs where oxygen passes into the bloodstream and carbon dioxide is removed.
With pneumonia, inflammation and infection develop within this normally air-filled lung tissue.
Fluid, inflammatory material and sometimes pus can accumulate within affected areas. This reduces the amount of healthy lung available for normal gas exchange.
In everyday terms, parts of the lung that should be light and full of air can become inflamed, wet and much less effective at transferring oxygen.
The severity depends on how much lung is involved, what caused the pneumonia, how quickly treatment begins and the general health of the horse.
What might an owner notice?
The signs can vary considerably between horses.
Possible signs include:
- fever or a temperature higher than normal
- coughing
- nasal discharge
- increased breathing rate
- deeper or more laboured breathing
- lethargy or appearing unusually quiet
- reduced appetite
- reluctance to exercise
- poor performance
- taking longer than expected to recover after exercise
- weight loss when illness is prolonged
- increased heart rate
- occasionally an unpleasant-smelling nasal discharge or breath where significant bacterial infection is present.
A horse does not have to show every sign.
Some horses initially appear simply "not quite right" before more obvious respiratory signs develop.
Terms you may hear your vet use
Understanding the terminology can make a diagnosis considerably less frightening and confusing.
Bacterial pneumonia
This means bacteria have established an infection within the lung.
The resulting immune response causes inflammation and the accumulation of fluid and inflammatory material in affected areas.
Your vet may take samples to help identify the bacteria involved and determine which antibiotics are most appropriate.
Viral pneumonia
Some respiratory viruses can cause inflammation deeper within the respiratory system and may involve the lungs themselves.
A viral infection can also damage the respiratory tract's normal defences, sometimes making it easier for a secondary bacterial infection to develop afterwards.
"Secondary" simply means that the bacterial infection developed following the original illness.
Aspiration pneumonia
Aspiration means that material that should have travelled down the oesophagus towards the stomach has instead entered the airway and lungs.
This might involve food, liquid, saliva or medication.
Because this material can carry bacteria and physically irritate the lung, significant pneumonia may follow.
Aspiration pneumonia can occur in horses experiencing swallowing difficulties, choke or certain neurological problems, and occasionally following incorrectly administered oral medication or fluids.
Pleuropneumonia
This is a term owners may hear particularly in seriously ill horses.
Pneumonia means inflammation or infection of the lung.
The pleura are the thin membranes surrounding the lungs and lining the inside of the chest.
Pleuropneumonia therefore means that both the lung and the surrounding pleural area are involved.
Fluid may accumulate within the chest around the lungs — known as pleural effusion — making normal lung expansion more difficult.
This can be a serious condition requiring intensive veterinary treatment.
Pleurisy or pleuritis
These terms mean inflammation of the pleura surrounding the lungs.
Because these membranes move against one another as the horse breathes, inflammation can make breathing painful.
A horse may consequently breathe more shallowly or appear reluctant to move.
Lung consolidation
If your vet says an area of lung is "consolidated", it does not mean the lung has become solid permanently.
It describes an area where the tiny air spaces that normally contain air have become filled with fluid and inflammatory material.
That portion of lung therefore becomes denser and cannot exchange gases normally.
Pulmonary abscess
Pulmonary simply means relating to the lungs.
An abscess is a localised pocket of infection containing pus.
A pulmonary or lung abscess can occasionally develop when infection becomes established within a particular area of lung tissue and may require prolonged veterinary treatment.
What can cause pneumonia?
There is no single cause.
Pneumonia may develop following:
- bacterial infection
- viral respiratory disease
- aspiration of food or fluid
- complications associated with choke
- impaired swallowing
- prolonged transport
- another illness that has weakened normal respiratory defences
- exposure to infectious respiratory disease
- circumstances in which bacteria can establish themselves within the lower respiratory tract.
Transport-associated pneumonia and pleuropneumonia are particularly well recognised in horses travelling long distances.
During prolonged transport, especially when the head is held relatively high for long periods, the horse has less opportunity to lower its head and naturally clear mucus and contaminants from the respiratory tract.
This is one reason good transport management and allowing horses opportunities to lower their heads are important.
How does a horse normally protect its lungs?
The respiratory system has several natural defence mechanisms.
Mucus traps dust, microorganisms and other particles entering the airways. Microscopic hair-like structures called cilia continually move this mucus upwards towards the throat where it can be swallowed or cleared.
This is sometimes described by vets as the mucociliary escalator.
A useful way to picture it is as the respiratory system's own continuously moving cleaning system.
Coughing provides another important defence by helping remove material from the airways.
When these protective mechanisms are overwhelmed or impaired, infection has a greater opportunity to reach and establish itself within the lower respiratory tract.
How might your vet investigate pneumonia?
The exact investigation depends on the individual horse and severity of illness.
Your vet may assess:
- temperature, heart rate and breathing rate
- breathing effort
- lung and airway sounds
- nasal discharge
- hydration
- blood tests
- respiratory samples
- ultrasound examination of the chest
- endoscopy of the respiratory tract
- occasionally radiography or other diagnostic procedures.
You may hear your vet talk about a tracheal wash or bronchoalveolar lavage (BAL).
Both involve collecting material from the respiratory tract so that the cells, mucus and potentially infectious organisms present can be examined.
These tests can help your vet understand what is happening deeper within the respiratory system rather than relying solely on what can be seen externally.
Treatment
Pneumonia is a condition in which treatment should be directed by a veterinary surgeon.
Treatment varies according to the cause and severity and may include:
- appropriate antibiotics where bacterial infection is present or suspected
- medication to control inflammation and fever
- fluids and supportive care
- management of pain
- treatment to help clear respiratory secretions where appropriate
- drainage of fluid from the chest in some cases of pleuropneumonia
- hospitalisation and intensive care in seriously affected horses.
Some horses recover relatively quickly.
More severe pneumonia or pleuropneumonia can require prolonged treatment and a lengthy period before the lungs and the horse's overall fitness have recovered sufficiently for normal work.
Recovery does not necessarily end when the infection has gone
This is an important point for owners.
A horse may appear brighter and have returned to a normal temperature before its lungs have completely recovered.
Inflammation may still be resolving, mucus clearance may still be occurring and fitness lost during illness must gradually be rebuilt.
Returning to strenuous exercise too early can place unnecessary demand on a respiratory system that is still recovering.
Your vet can advise when exercise should restart and how gradually workload should increase.
Supporting the horse during recovery
Alongside veterinary treatment, management can help reduce unnecessary demands on the respiratory system.
Depending upon veterinary advice, this may include:
- providing a clean, well-ventilated environment
- minimising dust
- avoiding mouldy forage or bedding
- maintaining appropriate hydration
- allowing adequate rest
- monitoring temperature and breathing
- observing appetite and water intake
- following medication instructions carefully
- returning to exercise gradually rather than immediately returning to the previous workload.
Good stable ventilation is particularly important.
A stable does not need to feel warm and enclosed to be comfortable for a horse. Horses generally tolerate cool air considerably better than an atmosphere containing accumulated dust, ammonia and airborne particles.
Monitor the horse, not just the cough
Coughing is an obvious respiratory sign, but it is only one part of the picture.
During illness and recovery it can be useful to monitor:
- rectal temperature
- breathing rate at rest
- breathing effort
- appetite
- water consumption
- nasal discharge
- demeanour
- coughing frequency
- willingness to move
- recovery following the gradual reintroduction of exercise.
Knowing what is normal for your own horse makes changes easier to recognise.
When should I call my vet?
Contact your vet promptly if you suspect pneumonia.
Particular reasons for veterinary assessment include:
- fever
- persistent coughing accompanied by illness or lethargy
- increased breathing rate at rest
- noticeably increased effort when breathing
- significant nasal discharge
- reduced appetite
- marked deterioration in performance
- a horse becoming unwell following a respiratory infection
- respiratory problems developing during or following prolonged transport
- suspected aspiration following choke or swallowing difficulties.
Seek urgent veterinary assistance if the horse is struggling to breathe, appears severely distressed, becomes markedly weak or deteriorates rapidly.
Respiratory difficulty should never be managed simply by waiting to see whether it improves.
Reducing respiratory challenges
Not every case of pneumonia can be prevented, but sensible management can reduce some risks.
Consider:
- maintaining good stable ventilation
- reducing unnecessary dust
- using good-quality forage and bedding
- appropriate vaccination
- sensible biosecurity during infectious respiratory outbreaks
- isolating horses showing signs of infectious respiratory disease
- monitoring horses carefully following long-distance transport
- allowing appropriate opportunities for horses to lower their heads during suitable breaks in prolonged journeys
- seeking veterinary advice promptly when a horse develops significant respiratory illness.
Preventing infectious disease from spreading between horses is particularly important on yards, at competitions and wherever horses regularly arrive and leave.
The bigger respiratory picture
Pneumonia is one of several conditions that can cause coughing or altered breathing in horses.
Other possibilities include:
- equine asthma
- influenza and other respiratory infections
- respiratory allergies and environmental irritation
- exercise-induced pulmonary haemorrhage (EIPH)
- upper airway disorders.
A cough describes a sign, rather than a diagnosis.
Finding out why the horse is coughing is therefore more important than simply trying to stop the cough.
Key message
Pneumonia means inflammation and infection have developed within the lungs themselves.
The affected parts of the lung become less effective at exchanging oxygen, and in severe cases the horse can become seriously ill.
Early veterinary assessment, appropriate treatment, good respiratory management and sufficient recovery time all matter.
And remember:
A horse that seems brighter is not necessarily a horse whose lungs have completely recovered.
Suggested graphics
Graphic 1 — Hero graphic
"Pneumonia in the Horse — What Happens Inside the Lungs?"
Purpose: Immediate visual explanation of what pneumonia actually means.
Show a horse with the respiratory tract subtly highlighted and an enlarged cutaway of healthy versus pneumonic lung.
Healthy lung: Open, air-filled structures allowing normal oxygen exchange.
Pneumonia: Inflamed areas containing fluid and inflammatory material, reducing the amount of functioning air-filled lung.
Suggested standalone wording:
Pneumonia in Horses
Pneumonia causes inflammation and infection within the lungs. Normally air-filled areas may become filled with fluid and inflammatory material, making normal oxygen exchange more difficult.
Watch for: Fever • Coughing • Nasal discharge • Increased breathing rate • Increased breathing effort • Lethargy • Reduced appetite
Breathing difficulty requires urgent veterinary attention.
Footer/identity:
JCG Equine Health Hub
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The JCG identity and website should remain visible if the graphic is downloaded, shared or printed independently of the webpage.
Graphic 2 — "What Do These Veterinary Terms Mean?"
A clear owner-friendly illustrated glossary.
Divide the chest/lung illustration into four labelled explanations:
Pneumonia
Inflammation and infection within the lung itself.
Aspiration pneumonia
Food, liquid or other material has entered the airway and caused inflammation or infection within the lung.
Pleuropneumonia
Both the lung and the space and membranes surrounding it are affected. Fluid may accumulate around the lungs.
Lung consolidation
Normally air-filled areas have become filled with fluid and inflammatory material and cannot exchange gases normally.
Small footer:
These descriptions explain commonly used veterinary terminology and are not intended to diagnose respiratory disease.
JCG Equine Health Hub | jcgsupplements.com
Graphic 3 — "Pneumonia: When to Call the Vet"
Designed to work particularly well as a downloadable or shareable owner reference.
Contact your vet promptly
Fever
Especially when accompanied by respiratory signs or lethargy.
Breathing faster than normal at rest
Know your horse's normal resting respiratory rate.
Increased breathing effort
The abdomen or nostrils may be working noticeably harder.
Coughing + an unwell horse
A cough combined with fever, lethargy or loss of appetite deserves investigation.
Significant nasal discharge
Particularly when accompanied by other signs of illness.
Problems following transport
Fever, coughing or lethargy following a long journey should not be ignored.
Following choke or suspected aspiration
Contact your vet if respiratory signs or fever develop.
URGENT
A horse struggling to breathe, showing severe respiratory distress or deteriorating rapidly requires urgent veterinary attention.
Footer:
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Owner education for better-informed equine health decisions
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Important information
The JCG Equine Health Hub provides general educational information for horse owners. It is not a substitute for examination, diagnosis or treatment by a veterinary surgeon.
Pneumonia can be a serious respiratory disease. If you are concerned about your horse's breathing or general health, contact your veterinary surgeon.