Strangles: A Comprehensive Guide for Horse Owners

Overview

Strangles is one of the most common and recognizable infectious diseases affecting horses worldwide. Caused by the bacterium Streptococcus equi subspecies equi, this highly contagious respiratory infection has been documented for centuries and continues to pose significant challenges for horse owners, trainers, and veterinarians today.

The disease gets its dramatic name from the characteristic swelling of lymph nodes in the head and neck region, which can become so severe that they appear to "strangle" the affected horse by obstructing breathing and swallowing. While the name sounds alarming, with proper veterinary care and management, most horses recover completely from strangles.

Understanding strangles is crucial for anyone involved with horses, as early recognition and appropriate response can significantly impact both individual horse health and prevent widespread outbreaks in equine facilities.

Causes

Strangles is caused exclusively by Streptococcus equi subspecies equi, a gram-positive bacterium that has evolved specifically to infect horses and other equids. This pathogen is highly adapted to the equine respiratory tract and has several characteristics that make it particularly effective at causing disease:

The bacteria primarily targets the mucous membranes of the upper respiratory tract, including the nasal passages, throat, and associated lymph nodes. Once established, S. equi produces various virulence factors that help it evade the horse's immune system and establish infection.

The bacterium spreads through direct contact between horses or indirect contact through contaminated surfaces, equipment, water sources, and even human handlers. Infected horses shed the bacteria in nasal discharge and pus from ruptured abscesses, creating environmental contamination that can persist for weeks under favorable conditions.

Factors that increase susceptibility include stress, transportation, overcrowding, poor ventilation, and mixing of horses from different locations. Young horses between 1-5 years of age are most commonly affected, though horses of any age can develop strangles if they haven't been previously exposed or vaccinated.

Symptoms & Signs

Early Symptoms

• Fever (often 102-106°F/39-41°C)
• Depression and lethargy
• Loss of appetite
• Clear nasal discharge that becomes thick and purulent
• Difficulty swallowing
• Mild coughing
• Swelling of lymph nodes under the jaw and throat

Advanced Symptoms

• Severe swelling of submandibular and retropharyngeal lymph nodes
• Thick, creamy yellow nasal discharge
• Difficulty breathing due to airway obstruction
• Extended head and neck posture
• Reluctance to lower head to eat or drink
• Formation of abscesses in swollen lymph nodes
• Spontaneous rupture of abscesses with pus drainage

Emergency Signs

• Severe respiratory distress or labored breathing
• Complete inability to swallow
• Blue or purple coloration of gums (cyanosis)
• Collapse or inability to stand
• Signs of "bastard strangles" (internal abscesses)
• High fever above 106°F (41°C) that doesn't respond to treatment

Diagnosis

Veterinary diagnosis of strangles involves several approaches, as accurate identification is crucial for proper treatment and outbreak control:

Clinical Examination: Veterinarians assess the characteristic signs including fever, nasal discharge, and lymph node swelling. The pattern of lymph node involvement and the nature of nasal discharge provide important diagnostic clues.

Laboratory Testing: Bacterial culture remains the gold standard for definitive diagnosis. Samples of nasal discharge or abscess material are cultured to identify S. equi. PCR (polymerase chain reaction) testing offers faster results and high accuracy, even when bacterial loads are low.

Blood Work: Complete blood counts often show increased white blood cell counts, indicating bacterial infection. Blood chemistry panels help assess overall health status and organ function.

Endoscopy: In some cases, endoscopic examination of the upper respiratory tract may be performed to assess the extent of infection and rule out complications.

Radiography: X-rays of the head and neck region can help identify internal abscesses or complications, particularly in cases of bastard strangles.

Treatment Options

Veterinary Treatment

• Antibiotic therapy (typically penicillin or other appropriate antibiotics)
• Anti-inflammatory medications to reduce swelling and pain
• Supportive IV fluid therapy if dehydration is present
• Hot compresses and poulticing of swollen lymph nodes
• Surgical drainage of mature abscesses when appropriate
• Tracheostomy in severe cases with airway obstruction
• Treatment of complications such as bastard strangles
• Monitoring for secondary infections

Home Care (Under Veterinary Supervision)

• Isolation of affected horses to prevent spread
• Providing soft, palatable feeds that are easy to swallow
• Ensuring constant access to fresh, clean water
• Maintaining warm, comfortable environment with good ventilation
• Regular monitoring of temperature and general condition
• Gentle cleaning of nasal discharge
• Applying warm compresses to swollen areas as directed
• Administering prescribed medications as instructed

Prevention

Prevention of strangles requires a multi-faceted approach combining good management practices with appropriate medical interventions:

Biosecurity Measures: Implement strict protocols for new horse arrivals, including quarantine periods of 2-3 weeks. Maintain separate equipment for different groups of horses and disinfect regularly.

Vaccination: While vaccines are available, their effectiveness is debated among veterinarians. Discuss vaccination strategies with your veterinarian based on your specific risk factors and local disease prevalence.

Facility Management: Ensure proper ventilation in stables, avoid overcrowding, and maintain clean water sources. Regular cleaning and disinfection of facilities, especially during outbreaks, is essential.

Health Monitoring: Implement regular health checks and temperature monitoring, especially during high-risk periods or after introducing new horses.

Education: Ensure all handlers understand the signs of strangles and proper hygiene practices to prevent spread.

Prognosis & Recovery

The prognosis for horses with uncomplicated strangles is generally excellent, with most horses making a complete recovery within 3-6 weeks. However, several factors influence the outcome:

Uncomplicated Cases: Horses that receive appropriate veterinary care early in the disease course typically recover fully without long-term effects. The natural course involves abscess formation, maturation, and rupture, followed by healing and resolution.

Complicated Cases: Approximately 10-20% of horses may develop complications such as bastard strangles (internal abscesses), purpura hemorrhagica (immune-mediated vasculitis), or chronic carriers. These conditions require more intensive treatment and have more guarded prognoses.

Immunity: Horses that recover from strangles typically develop strong, long-lasting immunity to reinfection. However, some horses may become chronic carriers, shedding bacteria intermittently without showing clinical signs.

When to See a Vet

Immediate veterinary attention is required if you observe:

• High fever (above 102°F/39°C) persisting for more than 24 hours
• Difficulty breathing or noisy breathing
• Inability to eat or drink normally
• Severe depression or lethargy
• Rapid swelling of lymph nodes in the head and neck
• Any signs of respiratory distress
• Thick, yellow nasal discharge
• Multiple horses showing similar symptoms

Early veterinary intervention significantly improves outcomes and helps prevent complications. Never delay seeking professional help when strangles is suspected, as the condition can progress rapidly and potentially become life-threatening.