# Strangles in Horses: A Comprehensive Guide for Horse Owners
Overview
Strangles is one of the most well-known and feared infectious diseases in horses, and for good reason. This highly contagious bacterial infection affects the upper respiratory tract and lymph nodes, causing significant discomfort and potentially serious complications if left untreated.
The disease gets its dramatic name from the way it can affect breathing when lymph nodes in the throat area become severely swollen. While the name sounds alarming, with proper veterinary care and management, most horses recover completely from strangles.
Strangles is caused by the bacterium Streptococcus equi subspecies equi, which specifically targets horses, donkeys, and mules. This pathogen has co-evolved with equines over thousands of years, making it highly adapted to infecting these animals.
The disease is endemic worldwide and can affect horses of any age, though young horses (6 months to 5 years) are most commonly affected. Adult horses can develop immunity through previous exposure, but this immunity can wane over time, leaving them susceptible to reinfection.
Understanding strangles is crucial for every horse owner, as early recognition and proper management can prevent severe complications and reduce the spread of infection to other horses in the barn or facility.
Causes
Strangles is caused exclusively by Streptococcus equi subspecies equi, a gram-positive bacterium that has adapted specifically to infect horses and related equids. This organism is highly host-specific and does not naturally infect other species of animals or humans.
The bacteria primarily targets the mucous membranes of the upper respiratory tract, including the nasal passages, throat, and associated lymph nodes. Once established, the infection causes characteristic swelling of the submandibular and retropharyngeal lymph nodes.
Several factors contribute to the development and spread of strangles:
Direct transmission occurs when horses come into direct contact with infected animals through nose-to-nose contact, shared water sources, or contaminated feed. The bacteria can survive in nasal discharge and pus from ruptured abscesses for extended periods.
Indirect transmission happens through contaminated equipment, clothing, hands of handlers, water troughs, feed buckets, and other surfaces that have been exposed to infected material. The bacteria can survive on surfaces for weeks under favorable conditions.
Airborne transmission can occur over short distances through respiratory droplets when infected horses cough or sneeze, though this is less common than direct contact transmission.
Carrier horses represent a significant challenge in strangles management. Some horses can harbor the bacteria in their guttural pouches (air-filled spaces connected to the throat) for months or even years without showing clinical signs, serving as a source of infection for other horses.
Environmental factors such as stress, overcrowding, poor ventilation, and concurrent illnesses can increase susceptibility to infection and worsen the severity of disease.
Symptoms & Signs
Strangles symptoms typically develop 3-14 days after exposure to the bacteria, with the incubation period varying based on factors such as the horse's immune status, stress levels, and the amount of bacterial exposure.
Early Signs
The earliest symptoms of strangles often resemble a common cold or mild respiratory infection:
- Mild fever (101-103°F) that may come and go initially
- Depression and lethargy as the horse begins to feel unwell
- Reduced appetite or reluctance to eat, especially hard feeds
- Clear nasal discharge that may be minimal at first
- Mild coughing or throat clearing sounds
- Slight swelling around the throat or jaw area that may be barely noticeable
Advanced Symptoms
As the infection progresses, typically within 1-2 weeks of initial exposure, more characteristic signs develop:
- High fever (103-106°F) that persists
- Thick, creamy nasal discharge that may be white, yellow, or greenish
- Pronounced swelling of lymph nodes under the jaw (submandibular) and around the throat
- Difficulty swallowing leading to reluctance to drink water or eat
- Extended head and neck posture as the horse tries to ease breathing difficulties
- Loud breathing sounds due to narrowed airways
- Formation of abscesses in swollen lymph nodes that may eventually rupture and drain pus
Emergency Signs
Certain symptoms require immediate veterinary attention as they indicate severe complications:
- Severe breathing difficulty or respiratory distress
- Blue-tinged gums or tongue indicating oxygen deprivation
- Inability to swallow water, leading to dehydration
- Excessive drooling or inability to close the mouth properly
- Collapse or extreme weakness
- Signs of bastard strangles including abdominal pain, neurological symptoms, or swelling in unusual locations
It's important to note that symptoms can vary significantly between horses, and some may show only mild signs while others develop severe complications. Any horse showing signs of upper respiratory infection should be evaluated by a veterinarian promptly.
Diagnosis
Accurate diagnosis of strangles is essential for proper treatment and infection control. Veterinarians use several diagnostic approaches, often in combination, to confirm the presence of Streptococcus equi.
Clinical Examination
The diagnostic process begins with a thorough clinical examination. Veterinarians look for the characteristic combination of symptoms including fever, nasal discharge, and lymph node swelling. The pattern and location of swollen lymph nodes, particularly the submandibular nodes under the jaw, are highly suggestive of strangles.
Laboratory Testing
Bacterial culture remains the gold standard for strangles diagnosis. Samples of nasal discharge, throat swabs, or pus from ruptured abscesses are cultured on blood agar plates. Streptococcus equi produces characteristic colonies that can be identified through biochemical testing. However, culture can take 24-48 hours for results.
PCR (Polymerase Chain Reaction) testing provides rapid, highly sensitive detection of S. equi DNA. This test can identify the bacteria even in small numbers and provides results within hours. PCR is particularly useful for detecting carrier animals or confirming infection in the early stages.
Antigen detection tests offer another rapid diagnostic option, providing results within minutes to hours. These tests detect specific proteins produced by S. equi bacteria.
Imaging
Ultrasound examination of the throat and neck area can reveal the extent of lymph node involvement and help identify abscesses that may not yet be palpable. This is particularly useful for monitoring abscess development and planning treatment.
Endoscopy may be performed to examine the guttural pouches, especially in cases where carrier status is suspected or in horses with complications.
Differential Diagnosis
Veterinarians must distinguish strangles from other conditions that cause similar symptoms, including viral respiratory infections, other bacterial pneumonia, lymphoma, or foreign body obstructions.
Treatment Options
Treatment of strangles requires careful veterinary supervision and a tailored approach based on the stage of infection and severity of symptoms. The goal is to support the horse through the infection while preventing complications and limiting spread to other animals.
Veterinary Treatment
Antibiotic therapy is controversial in strangles treatment. While antibiotics can be effective, their use must be carefully timed. Early treatment with antibiotics like penicillin or trimethoprim-sulfamethoxazole may prevent abscess formation if given within the first few days of infection. However, if abscesses have already begun forming, antibiotics may actually prolong the infection by preventing proper drainage.
Anti-inflammatory medications such as phenylbutazone or flunixin meglumine may be prescribed to reduce fever and inflammation, making the horse more comfortable and encouraging eating and drinking.
Surgical drainage of mature abscesses may be necessary if they don't rupture naturally. This should only be performed by a veterinarian under sterile conditions to prevent secondary bacterial infections.
Supportive fluid therapy may be required for horses that become dehydrated due to difficulty swallowing or reduced water intake.
Nursing Care
Isolation is critical to prevent spread to other horses. Infected horses should be kept in a separate area with dedicated equipment and handlers.
Nutritional support focuses on providing easily consumed, high-quality nutrition. Soft feeds like bran mashes, soaked pellets, or hay that's been dampened or chopped finely can encourage eating when swallowing is difficult.
Environmental management includes ensuring good ventilation while avoiding drafts, maintaining comfortable temperatures, and providing deep, clean bedding.
Monitoring for complications requires daily assessment of temperature, appetite, breathing pattern, and the progression of swelling or abscess development.
Complications Management
Bastard strangles, where abscesses form in unusual locations like the abdomen or brain, requires aggressive antibiotic treatment and intensive supportive care.
Purpura hemorrhagica, an immune-mediated vasculitis that can develop weeks after apparent recovery, requires immediate corticosteroid treatment and intensive monitoring.
Carrier state management involves identifying horses that continue to harbor bacteria in their guttural pouches and treating them with specific protocols to eliminate the infection.
Home Care
While professional veterinary care is essential for strangles, horse owners play a crucial role in supportive care and monitoring.
Daily Care Routine
Maintain strict biosecurity protocols including dedicated clothing, boots, and equipment for the infected horse. Wash hands thoroughly and change clothes before handling other horses.
Provide easily digestible, soft foods and ensure fresh water is always available. Slightly warm water may be more appealing to horses with sore throats.
Monitor vital signs daily, including temperature, respiratory rate, and general attitude. Keep detailed records to share with your veterinarian.
Gently clean nasal discharge with warm water and soft cloths, but avoid forcing drainage or manipulating swollen areas.
Environmental Management
Maintain good ventilation in housing areas while protecting from drafts. Dust-free environments help reduce respiratory irritation.
Provide comfortable, deep bedding and ensure the horse has room to maintain their preferred head position for easier breathing.
Remove other horses from the immediate area and implement quarantine protocols as directed by your veterinarian.
When Home Care Isn't Enough
Recognize that some cases require hospitalization, particularly when breathing becomes severely compromised or the horse stops eating and drinking entirely.
Prevention
Preventing strangles requires a multi-faceted approach combining biosecurity, management practices, and in some cases, vaccination.
Biosecurity Measures
Implement quarantine protocols for all new horses entering the property. A minimum 2-3 week isolation period allows for observation and testing before introducing horses to the general population.
Maintain separate equipment for different groups of horses, or thoroughly disinfect shared items between uses. Pay particular attention to water buckets, feed tubs, and grooming tools.
Control human traffic and require visitors to follow biosecurity protocols including hand washing and potentially changing clothes when moving between horse groups.
Regular health monitoring of all horses helps identify potential problems early. Daily observation for signs of illness should be part of routine care.
Facility Management
Avoid overcrowding and ensure good ventilation in all horse housing areas. Stress reduction helps maintain strong immune function.
Maintain proper nutrition and preventive health care including regular vaccinations for other diseases, dental care, and parasite control.
Design facilities to minimize nose-to-nose contact between horses when possible, particularly in high-risk situations like horse shows or sales.
Vaccination Considerations
Strangles vaccines are available but have limitations. Intramuscular vaccines provide limited protection and may cause adverse reactions. Intranasal vaccines offer better protection but are not suitable for all horses.
Vaccination decisions should be made in consultation with a veterinarian based on individual risk factors and local disease prevalence.
Prognosis & Recovery
The prognosis for horses with strangles is generally good when the infection is recognized early and managed appropriately. Most horses recover completely with proper care, though the timeline can vary significantly.
Typical Recovery Timeline
Acute phase typically lasts 2-4 weeks, during which fever, nasal discharge, and lymph node swelling are most prominent. Abscesses usually develop and rupture during this period.
Recovery phase spans an additional 2-4 weeks as drainage decreases, swelling resolves, and appetite returns to normal. Some horses may have persistent nasal discharge for several weeks after other symptoms resolve.
Return to full activity usually occurs 4-6 weeks after initial symptoms appeared, provided there are no complications and the horse has been cleared by veterinary examination.
Factors Affecting Recovery
Young, healthy horses generally recover more quickly and completely than older animals or those with concurrent health issues.
Early recognition and appropriate treatment improve outcomes and reduce the risk of complications.
Proper supportive care and nutrition during illness significantly impact recovery time and success.
Long-term Considerations
Most horses develop strong immunity after recovering from strangles, providing protection against reinfection for several years. However, immunity can wane over time.
Some horses may become carriers, harboring bacteria in their guttural pouches without showing symptoms. These horses can be a source of infection for others.
Rarely, horses may develop chronic complications such as guttural pouch empyema or recurrent respiratory problems.
When to See a Vet
Strangles requires professional veterinary attention, and certain situations demand immediate emergency care.
Immediate Emergency Situations
Severe breathing difficulty or respiratory distress requires emergency veterinary attention. Signs include nostril flaring, loud breathing sounds, or blue-tinged gums.
Inability to drink water or swallow saliva can quickly lead to dehydration and requires immediate intervention.
Extreme lethargy, collapse, or signs of severe pain indicate potential complications requiring urgent care.
Routine Veterinary Care Needed
Any horse showing signs of upper respiratory infection should be examined by a veterinarian for proper diagnosis and treatment planning.
Horses with confirmed or suspected strangles need regular veterinary monitoring throughout the course of illness.
Post-recovery examination ensures complete resolution and clearance before returning to normal activities or contact with other horses.
Follow-up Care
Carrier testing may be recommended 4-6 weeks after apparent recovery, particularly for horses that will be traveling or mixing with new groups.
Annual health examinations should include discussion of strangles risk factors and prevention strategies.
Remember that early intervention and proper veterinary care significantly improve outcomes and reduce the risk of serious complications. Never hesitate to contact your veterinarian if you have concerns about your horse's health.