Strangles: What Owners Should Know

Strangles is one of the most common infectious diseases affecting horses worldwide, caused by the bacterium Streptococcus equi subspecies equi. Despite advances in veterinary medicine, this highly contagious respiratory infection continues to challenge horse owners and trainers, particularly in facilities with multiple horses or frequent turnover of animals. Understanding strangles is essential for any horse owner, as early recognition and proper management can significantly reduce the severity of the disease and prevent it from spreading to other horses on your property.

This article provides horse owners with evidence-based information about strangles symptoms, transmission, treatment options, and prevention strategies. While this guide offers comprehensive knowledge about the disease, it is not a substitute for professional veterinary diagnosis and treatment. If you suspect your horse has strangles or any signs of respiratory illness, contact your equine veterinarian immediately. For emergency situations such as difficulty breathing or inability to swallow, call your veterinarian right away or contact an emergency equine clinic.

What is Strangles?

Strangles gets its name from the characteristic swelling of the lymph nodes in the throat area, which can occasionally obstruct the airway and create breathing difficulties. The disease is caused by Streptococcus equi, a gram-positive coccus bacterium that targets the lymph nodes and tissues of the upper respiratory tract. Once a horse is infected, the bacteria multiply in the lymphoid tissue, triggering an inflammatory response that results in the classic symptoms horse owners recognize.

The disease has been documented in horses for centuries and remains prevalent because the bacteria is resilient and spreads easily between animals. Strangles is reportable in some states and regions, meaning veterinarians may be required to report confirmed cases to agricultural authorities. The infection typically follows a predictable course, progressing through distinct stages over several weeks if left untreated.

Clinical Signs and Symptoms

Recognizing the early signs of strangles is crucial for prompt treatment and containment. Symptoms typically appear 3 to 14 days after exposure to the bacterium, though the incubation period can extend up to 2 weeks in some cases.

Early Signs (Days 1-3)

• Fever, typically 101.5 to 104 degrees Fahrenheit
• Depression and lethargy
• Decreased appetite
• Nasal discharge, initially clear and serous, progressing to purulent (pus-like)
• Cough, usually dry initially
• Reluctance to lower the head to eat or drink

Progressive Signs (Days 4-10)

• Swelling of the submandibular (under the jaw) and retropharyngeal lymph nodes
• Throat pain making swallowing difficult
• Visible purulent nasal discharge, often from one or both nostrils
• Swollen and inflamed gums and throat tissues
• Difficulty eating hay but may consume soft feed or grain
• Weight loss becomes apparent
• Continued elevated temperature

Advanced Signs

• Significant enlargement of throat lymph nodes with hardened, abscess-like formations
• Drainage of thick, creamy purulent material from lymph node abscesses
• Breathing difficulty if airway is obstructed (emergency situation)
• Difficulty drinking water; some horses develop quidding (dropping feed from the mouth)

The severity of clinical signs varies considerably between horses. Some horses experience mild symptoms and recover relatively quickly, while others develop severe abscesses that rupture and drain externally. The drainage typically occurs 7 to 10 days after symptom onset, followed by gradual improvement. Complete recovery usually takes 2 to 6 weeks from the onset of symptoms.

Transmission and Contagion Risk

Strangles spreads rapidly between horses through direct contact with infected nasal secretions and purulent drainage from abscesses. The bacterium can also spread indirectly through contaminated equipment, feed buckets, water troughs, fencing, grooming supplies, and human hands. A single infected horse can transmit the disease to many others, particularly in facilities where horses share equipment or living spaces.

Horses are most contagious during the acute phase of illness and while actively draining pus from abscesses. Some recovered horses may continue shedding bacteria intermittently for weeks after clinical recovery, particularly in the nasal passages. These chronic carriers, sometimes called “shedders,” can transmit infection to susceptible horses even without showing obvious symptoms themselves.

Risk factors for strangles transmission include:

• High population density of horses
• Poor ventilation in barns and stables
• Shared water and feed supplies
• Lack of sanitation protocols
• Introduction of new horses without quarantine periods
• Stress from transport, competition, or environmental changes
• Young horses (under 5 years old) and immunocompromised animals

Diagnosis

Your equine veterinarian will diagnose strangles based on clinical signs, physical examination findings, and laboratory confirmation. Diagnostic methods include:

• Culture: Samples of nasal discharge or purulent material from abscesses are cultured to isolate and identify Streptococcus equi. This is the gold standard for diagnosis.
• PCR testing: Polymerase chain reaction tests can rapidly detect bacterial DNA in nasal swabs or drainage samples, often providing results within 24 hours.
• Guttural pouch endoscopy: In some cases, the veterinarian may examine the guttural pouches (air sacs in the throat) with an endoscope to assess the extent of infection.
• Ultrasound: Ultrasonic examination can detect enlarged lymph nodes and abscesses, helping assess disease severity.

Do not assume a horse has strangles based on symptoms alone, as other respiratory conditions such as influenza, rhinovirus, or bacterial pneumonia present similarly. Confirmed diagnosis is essential for proper treatment planning and disease management.

Treatment Approaches

Treatment of strangles depends on the stage of disease and can involve antibiotics, supportive care, and drainage management. Treatment decisions should always be made in consultation with your veterinarian.

Antibiotic Therapy

Antibiotics are effective when started early in the disease, ideally before abscess formation occurs. However, once abscesses have formed and begun to mature, antibiotics penetrate poorly into the abscess cavity, reducing effectiveness. Commonly used antibiotics include penicillin G, procaine penicillin, or other appropriate agents selected based on culture sensitivity. Course lengths typically range from 7 to 10 days.

The timing of antibiotic administration is critical: early treatment with antibiotics before abscess rupture may reduce the severity and duration of illness. However, antibiotics given after abscesses have matured may actually prolong recovery by preventing natural abscess drainage.

Supportive Care

• Rest: Affected horses require stall rest and isolation to minimize stress and prevent transmission.
• Nutrition: Provide soft feed such as grain mush, alfalfa pellets soaked in water, or beet pulp. Some horses benefit from high-quality hay chaff or senior feed formulas.
• Hydration: Ensure access to clean water. If swallowing is painful, water can be offered in buckets so horses can drink at their own pace.
• Pain management: Nonsteroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone help reduce fever, pain, and inflammation.
• Warm compresses: Applying warm packs to swollen areas may provide comfort and promote abscess maturation.

Abscess Drainage

If abscesses mature and form visible, soft swellings, your veterinarian may recommend drainage to accelerate recovery. Some abscesses rupture and drain naturally, while others may require lancing or needle aspiration to encourage drainage. Proper drainage technique is important to prevent complications and infection of the drainage site.

Prevention and Biosecurity

Preventing strangles outbreaks requires a comprehensive biosecurity approach, particularly in facilities with multiple horses or those that interact with horses from different premises.

Quarantine Protocols

New arrivals should be quarantined for a minimum of 2 weeks in a separate facility with no direct contact with established horses. If the new horse has been exposed to strangles recently, extend quarantine to 4 weeks. During quarantine, observe for any signs of illness and request recent vaccination and health records from the previous owner.

Sanitation and Hygiene

• Use dedicated, color-coded equipment for sick horses that is not shared with healthy animals.
• Disinfect feed and water buckets, grooming supplies, and tack regularly using appropriate disinfectants.
• Wash hands thoroughly between handling sick and healthy horses.
• Clean water troughs frequently and maintain separate waterers for quarantined animals.
• Disinfect barn surfaces, fencing, and handling equipment with approved equine disinfectants.

Vaccination

Strangles vaccines are available, though they do not provide complete protection against infection. Available vaccines include intramuscular injections and intranasal formulations. Intranasal vaccines are thought to provide superior mucosal immunity. Vaccination is recommended for horses at high risk, such as those in boarding facilities, show horses, or animals in regions with documented strangles prevalence. Discuss vaccination protocols with your veterinarian to determine the appropriate schedule for your horse.

Complications

While most horses recover completely from strangles, complications can develop, particularly if the disease progresses untreated or if abscesses rupture internally rather than externally.

Bastard Strangles

Bastard strangles, also called internal strangles, occurs when infection spreads to distant lymph nodes throughout the body, causing abscesses in the lungs, liver, kidneys, or other organs. This complication can develop weeks or months after initial recovery and presents with recurrent fever, lethargy, and weight loss. Bastard strangles is difficult to treat and carries a poorer prognosis than classic strangles.

Guttural Pouch Empyema

Pus accumulation in the guttural pouches can obstruct the airway or rupture into surrounding tissues. This condition requires aggressive treatment and sometimes surgical intervention.

Airway Obstruction

Severe swelling of the lymph nodes or abscess rupture into the airway can compromise breathing. This is an emergency situation requiring immediate veterinary attention and possibly emergency tracheostomy placement.

Recovery and Long-Term Outlook

The prognosis for uncomplicated strangles is generally good. Most horses recover fully within 2 to 6 weeks, depending on the severity of infection and how early treatment was initiated. Following recovery, horses develop immunity to strangles that is usually long-lasting, making reinfection uncommon.

During recovery, gradually return to normal activity as the horse improves. Begin with short, hand-walking sessions and progress to ridden work only after the horse has been symptom-free for at least 1 week. Avoid strenuous exercise during the acute illness phase, as this can prolong recovery and increase the risk of complications.

Frequently Asked Questions

Can vaccinated horses get strangles?

Yes, vaccinated horses can contract strangles, though vaccination significantly reduces the severity of clinical signs and the duration of illness. Vaccines provide protection but not complete immunity, so vaccinated horses may develop milder disease if exposed to the bacterium.

How long after symptoms begin should I call my veterinarian?

Contact your veterinarian immediately if you notice signs of strangles such as fever, nasal discharge, throat swelling, or difficulty swallowing. Early veterinary involvement improves outcomes. If your horse develops difficulty breathing, cannot swallow, or seems in severe distress, call your veterinarian or emergency clinic right away.

Is strangles contagious to humans?

No, strangles does not affect humans. You cannot contract the disease from infected horses, though you can transmit the bacteria to other horses through contaminated hands or equipment. Always practice good hygiene when handling sick horses.

Can a horse be a chronic carrier of strangles?

Yes, some horses become chronic carriers and shed Streptococcus equi intermittently for months after clinical recovery, particularly in the guttural pouches and nasal passages. Carriers can transmit infection to susceptible horses. Repeated culture testing can help identify chronic carriers, though eliminating the carrier state is challenging.

Key Takeaways

• Strangles is a highly contagious bacterial respiratory disease caused by Streptococcus equi that spreads rapidly between horses through direct and indirect contact.
• Early signs include fever, lethargy, nasal discharge, and throat pain; progressive signs include swollen lymph nodes and abscess formation, typically appearing 3 to 14 days after exposure.
• Diagnosis requires culture or PCR testing of nasal discharge or abscess material; do not rely on clinical signs alone, as other respiratory infections present similarly.
• Early antibiotic treatment reduces disease severity, but antibiotics are less effective once abscesses have matured; supportive care and pain management are essential components of treatment.
• Recovery typically takes 2 to 6 weeks, with most horses making complete recoveries and developing long-lasting immunity.
• Prevention requires strict quarantine of new horses, excellent sanitation practices, dedicated equipment for sick animals, and consideration of vaccination for high-risk horses.
• Complications including bastard strangles, guttural pouch infection, and airway obstruction can develop; contact your veterinarian immediately if breathing difficulty occurs.
• This article is not a substitute for professional veterinary care; always consult your equine veterinarian for diagnosis, treatment decisions, and guidance specific to your horse.

See also: Pigeon Fever and Equine Influenza — two other infectious diseases that share biosecurity protocols with strangles.