Pigeon Fever in Horses: Symptoms, Abscesses, and Treatment

By Dr Duncan Houston

Pigeon fever is one of those diseases that can look simple at first and turn complicated if it is handled badly. A horse may start with a soft swelling on the chest or lower belly, seem otherwise fairly bright, and then suddenly need careful drainage, isolation, and close monitoring.

The name sounds almost harmless, but the disease is not. Some horses only develop external abscesses and recover well. Others develop deeper infection, weight loss, fever, or internal abscesses that are much more serious. The key is knowing which form you may be dealing with and what to do next.

Quick Answer

Pigeon fever is a bacterial infection in horses caused by Corynebacterium pseudotuberculosis. It most commonly causes abscesses on the chest, lower abdomen, or limbs, but in some horses it can spread internally and become much more serious. Early veterinary assessment, proper abscess management, fly control, and strict hygiene are the most important parts of treatment and prevention.

What Matters Most

• A soft swelling on the chest or belly in fly season should raise suspicion for pigeon fever

• External abscesses are the most common form, but internal disease is the real concern

• Using antibiotics too early in simple external abscess cases can delay maturation and drainage

• Good fly control, drainage hygiene, and isolation matter just as much as treatment

What Is Pigeon Fever?

Pigeon fever is caused by the bacterium Corynebacterium pseudotuberculosis.

It gets its name from the classic swelling that can appear in the pectoral region, giving the horse a pigeon-breasted appearance. In practice, this is often the first thing owners notice.

This disease can affect horses in different ways:

• External abscesses

• Internal abscesses

• Ulcerative lymphangitis involving the limbs

The form of disease matters because it changes the urgency, treatment plan, and prognosis.

How Does It Spread?

Pigeon fever usually spreads through:

• Flies carrying bacteria from wounds, drainage, or contaminated material

• Contaminated soil, bedding, manure, or dusty environments

• Shared grooming tools, tack, or equipment if hygiene is poor

The bacteria often enter through small skin wounds or irritated areas.

In real-world cases, hot, dry weather and heavy fly pressure often set the stage. That is when cases tend to cluster.

Where Is It Found?

Historically, pigeon fever was strongly associated with the western United States, especially California. It is now seen much more widely, including in Texas and other regions where warm weather, dry conditions, and flies support transmission.

The pattern to remember is this: dry climate plus flies plus skin breaks equals higher risk.

What Are the Signs of Pigeon Fever?

Signs depend on which form is present.

Common early signs

• Soft swelling on the chest, lower abdomen, or along the midline

• Mild fever

• Reduced appetite

• Mild lethargy

More obvious external disease

• A warm, painful swelling that enlarges over days

• Thick pus once the abscess matures and drains

• Local discomfort but otherwise fairly normal behavior in some horses

More serious signs

• Persistent fever

• Weight loss

• Colic-like signs

• Limb swelling with draining tracts

• Ongoing depression or poor performance

Clinical insight

The mistake I see most often is assuming every swelling is minor because the horse still looks relatively well. External abscesses are common, but persistent fever, weight loss, or repeated swellings should make you think about internal disease.

The Three Forms of Pigeon Fever

External Abscesses

This is the most common form.

Abscesses often develop:

• In the pectoral region

• Along the lower abdomen

• Occasionally in other superficial sites

They typically swell over several days, then either rupture on their own or are drained by a veterinarian.

This form is usually the least dangerous, but poor handling can spread infection around the property.

Internal Abscesses

This is much less common, but far more serious.

Abscesses can form in internal organs such as:

• Liver

• Lungs

• Kidneys

• Spleen

These horses may show:

• Ongoing fever

• Weight loss

• Recurrent colic

• Depression

• Abnormal bloodwork

This form often needs prolonged treatment and careful monitoring.

Ulcerative Lymphangitis

This form affects the limbs, usually the hind legs.

You may see:

• Marked swelling

• Pain

• Draining tracts

• Thick discharge

• Reduced willingness to move

This form can be stubborn and often requires more aggressive treatment than a simple chest abscess.

Severity Framework

Mild

• Single external swelling

• Horse still bright and eating

• Little or no fever

Action: Veterinary confirmation and monitoring are still recommended

Moderate

• Abscess enlarging over days

• Mild fever or discomfort

• Early drainage or local pain

Action: Vet assessment within 24 hours is a good idea

High risk

• Multiple swellings

• Limb involvement

• Persistent fever

• Reduced appetite or weight loss

Action: Prompt veterinary workup is needed

Critical

• Suspected internal abscesses

• Significant depression

• Recurrent colic

• Ongoing weight loss

• Lab abnormalities suggesting systemic disease

Action: Urgent veterinary care and a full diagnostic plan are needed

How Do Vets Diagnose It?

Diagnosis depends on the form of disease.

For external abscesses

Diagnosis is often based on:

• Location and appearance of swelling

• Clinical examination

• Sampling of discharge when needed

For suspected internal disease

Your vet may recommend:

• Bloodwork

• Ultrasound

• Culture or PCR in some cases

• Monitoring inflammatory markers such as fibrinogen or serum amyloid A

The real question is not just “is this pigeon fever?” It is also “is this only external, or is there evidence of deeper disease?”

When Is This an Emergency?

Seek urgent veterinary care if your horse has:

• Persistent or high fever

• Weight loss

• Colic signs

• Severe limb swelling

• Difficulty moving

• Recurrent abscesses

• Depression or poor appetite lasting more than 24 hours

A simple external abscess is often manageable. Internal abscesses are where this disease becomes far more dangerous.

What Should You Do Right Now?

If you notice a suspicious swelling

• Isolate the horse from others

• Do not squeeze, lance, or open the swelling yourself

• Contact your veterinarian for an examination

If an abscess starts draining

• Keep the area clean

• Contain drainage material carefully

• Disinfect any contaminated surfaces

• Wear gloves and wash hands thoroughly

If your horse is unwell

• Check temperature

• Monitor appetite, manure, and attitude

• Watch for colic signs or worsening lethargy

What not to do

• Do not start antibiotics without veterinary advice in straightforward external abscess cases

• Do not share halters, brushes, buckets, or tack

• Do not leave drainage material in the environment

Treatment Strategies

External Abscesses

For uncomplicated external abscesses:

• Antibiotics are often avoided early because they can delay maturation

• The goal is usually to let the abscess ripen

• Your vet may lance and drain it under controlled conditions

• Daily flushing and wound care are often needed afterward

This is one of the most important practical points. Owners often want to start antibiotics immediately, but in many straightforward abscess cases that is not the best move.

Internal Abscesses

Internal disease is different.

These horses often need:

• Long courses of antibiotics

• Repeat bloodwork

• Ultrasound monitoring

• Careful reassessment over time

Treatment may continue for weeks and sometimes longer depending on response.

Ulcerative Lymphangitis

This form often requires:

• Systemic antibiotics

• Anti-inflammatory treatment

• Wound care

• Bandaging or hydrotherapy in some cases

Common Mistakes

• Treating every swelling as minor

• Starting antibiotics too early in a simple external abscess case

• Draining abscesses at home without veterinary guidance

• Letting pus contaminate stalls, yards, or shared areas

• Underestimating the risk of internal infection

• Failing to isolate affected horses

Prevention That Actually Works

Fly control

• Use sprays, masks, fans, and manure management

• Reduce fly breeding areas

• Be more aggressive in hot, dry months

Environmental hygiene

• Clean drainage sites thoroughly

• Disinfect tools and equipment

• Dispose of contaminated bedding carefully

Biosecurity

• Isolate infected horses

• Do not share grooming tools, halters, or tack

• Keep water and feed equipment separate

Skin care

• Manage wounds promptly

• Reduce opportunities for bacteria to enter through broken skin

There is no shortcut here. Prevention is mostly about lowering fly pressure and avoiding contamination.

Frequently Asked Questions

Is there a vaccine for pigeon fever?

There is no widely used commercial vaccine for horses at this stage.

Should all horses with pigeon fever get antibiotics?

No. Simple external abscesses are often managed differently from internal disease. Antibiotics are not always the right first step.

How long should a horse be isolated?

Isolation often continues until drainage has stopped and contamination risk is controlled. Your vet should guide this based on the case.

Can pigeon fever come back?

Yes. Some horses can have recurrent problems, and new infections can occur if fly pressure and environmental contamination are not controlled.

Pigeon fever is often manageable when it stays external, but it becomes far more serious when internal abscesses or limb involvement develop. The most important decisions are recognising suspicious swellings early, not rushing into the wrong treatment, and keeping drainage and flies under control so the disease does not spread through the barn.

If you are unsure whether a swelling is a simple abscess or something more concerning, ASK A VET™ can help you work through the next steps and when to involve your veterinarian urgently.