📋 At a Glance
⚠️ Signs Requiring Veterinary Contact
- Fever above 103°F in any horse — especially if multiple horses at a facility are affected
- Thick yellow-green nasal discharge from one or both nostrils
- Swollen, painful, warm lymph nodes under the jaw, between the jaw branches, or at the throatlatch
- Difficulty swallowing, extended neck position, or apparent discomfort when eating
- Reluctance to eat or drink combined with any respiratory sign
- Any horse that has been to an event, sale, or clinic in the past 2–3 weeks showing these signs
- Multiple horses in a barn developing similar signs — potential outbreak requiring veterinary-directed quarantine
The Clinical Course of Strangles
S. equi infects the mucosa of the upper respiratory tract — the pharynx, nasal passages, and guttural pouches — and then drains to the regional lymph nodes. The submandibular lymph nodes (under the jaw) and retropharyngeal lymph nodes (between the jaw branches, deep in the throatlatch area) are most commonly affected. As the bacteria replicate within these nodes, the tissue swells, becomes painful, and ultimately forms abscesses filled with thick, creamy pus.
These abscesses typically rupture over 7–14 days, either externally (through the skin) or into the guttural pouches. The drainage of pus marks the peak of environmental contamination — infected pus contaminates stall walls, bedding, water sources, fences, and feed equipment, where S. equi can survive for weeks in cool, moist conditions.
Most horses recover fully from uncomplicated strangles within 3–6 weeks. However, a significant minority develop complications — internal abscesses (bastard strangles) in lymph nodes of the chest, abdomen, or brain (most serious); purpura hemorrhagica (immune-mediated vasculitis causing severe edema and tissue death); and persistent guttural pouch infection that converts horses to chronic carriers.
Outbreak Management — Biosecurity Protocols
When strangles is suspected or confirmed in a barn, implementing biosecurity measures immediately limits spread. Your veterinarian will direct specific protocols. The following represents general educational guidance:
| Action | When | Why |
|---|---|---|
| Isolate affected horses | Immediately when signs appear | Limits environmental contamination and direct transmission |
| Temperature monitor all horses | Twice daily throughout outbreak | Fever is often the first sign — catches horses before drainage begins |
| Stop horse movement on/off property | Immediately | Prevents spread to other facilities |
| Notify exposed contacts | After veterinary confirmation | Facilities your horses visited in past 2–3 weeks may have exposed horses |
| Dedicate equipment to affected horses | Immediately | Shared halters, buckets, ropes transmit S. equi effectively |
| Disinfect high-touch surfaces | Daily during active outbreak | S. equi survives weeks on surfaces; most disinfectants effective on clean surfaces |
| Guttural pouch testing | After all horses recover | Identifies carriers before returning to group settings |
Antibiotic Use — A Nuanced Decision
The use of antibiotics in strangles management is one of the most contested topics in equine medicine, and one where veterinary guidance is essential. The conventional concern is that penicillin given to a horse in the early stages of infection — before abscesses have formed — may abort the immune response without clearing the bacteria, potentially converting the horse to a carrier or delaying and worsening the eventual disease course.
However, antibiotics ARE clearly indicated in specific situations: horses that are systemically ill, those with bastard strangles (internal abscesses), horses with high fever and severe dysphagia (difficulty swallowing), and immunocompromised horses. Your veterinarian determines the appropriate management for each horse individually based on the stage and severity of disease.
Complications — Recognizing Serious Outcomes
While most strangles cases are self-limiting, a subset develop potentially life-threatening complications that require intensive veterinary management.
Major Complications
- Bastard strangles: internal abscesses in mesenteric, thoracic, or hepatic lymph nodes — produces chronic weight loss, fever, colic, and respiratory signs; may not be apparent for weeks to months after initial infection
- Purpura hemorrhagica: immune-mediated vasculitis following S. equi infection — produces severe edema of the limbs, head, and body; petechial hemorrhages on mucous membranes; potentially fatal without treatment
- Guttural pouch empyema: accumulated pus in the guttural pouches requires veterinary treatment — lavage, drainage, and often systemic antibiotics to prevent chondroid formation
- EHV concurrent disease risk: stress of strangles may reactivate latent EHV; outbreaks can involve multiple pathogens
Vaccination — Protection and Limitations
Strangles vaccines are available but offer limited protection compared to many other equine vaccines. Two types are available: killed intramuscular products and a modified live intranasal product. Neither provides complete protection against infection, but vaccination appears to reduce severity of disease in vaccinated horses.
Important considerations: vaccination should not be given during an active outbreak; the modified live intranasal vaccine carries risk of causing lymph node swelling if accidentally administered to sites other than the nasal mucosa; horses with prior natural infection may mount very strong (and potentially harmful purpura-triggering) immune responses to killed vaccine — discuss with your vet before vaccinating horses with known prior infection or high titers.
✅ Action Steps — While Contacting Your Vet
- Isolate any horse with fever or nasal discharge immediately — do not wait for confirmation before isolating
- Call your veterinarian — describe signs, duration, number of horses affected, and recent movement history
- Take temperatures on all horses twice daily — fever is often the only early sign
- Notify facilities your horses attended in the past 2–3 weeks
- Implement equipment and handler biosecurity — dedicated items for affected horses; change clothing between barns
- Do not vaccinate during an active outbreak — discuss timing with your veterinarian
📋 Prevention & Long-Term Management Discussion Points
- Guttural pouch endoscopy and culture after recovery — identifies carriers before return to group settings
- Vaccination protocol once the outbreak has resolved and horses have recovered
- New horse quarantine protocol — minimum 21-day isolation for all new arrivals before herd introduction
- Environmental persistence — S. equi survives weeks on wood surfaces; wooden stall surfaces may need replacement after severe outbreaks
- Event biosecurity — understanding the risks of shows and clinics and protocols that reduce them
Questions to Ask Your Veterinarian
- Should we culture the nasal discharge to confirm S. equi, and does that change anything about our management?
- Which horses should receive antibiotics, and what product and duration do you recommend?
- How do you want me to manage the abscesses when they mature — apply warm compresses, allow natural rupture, or have you lance them?
- How long should we maintain isolation before reintroducing horses to the main herd?
- Which horses should have guttural pouch evaluation to rule out carrier status?
- When is it safe to vaccinate remaining horses, and which vaccine do you prefer for our situation?
