Equine Strangles

Strangles Overview

Strangles is a highly contagious bacterial infection in equines caused by Streptococcus equi subspecies equi. This gram-positive bacterium primarily infects the upper airway and lymph nodes of the head and neck. The disease, first documented in 1251, affects young horses more commonly and can recur on farms with past outbreaks.

Key Facts:

Prevalence: ~30% of equine infections are caused by S. equi.
Morbidity: Approaches 100%; Mortality: 3%-20%.
Recovery: Most horses recover without complications, though some may develop severe issues like metastatic infection (bastard strangles), immune-mediated diseases (e.g., purpura hemorrhagica), muscle pain, colic, diarrhea, or pleuropneumonia.

Symptoms:

Hallmark signs:

Fever (>101.5°F / 38.6°C).
Nasal discharge (initially clear, later purulent).
Swollen, abscessed lymph nodes (submandibular, retropharyngeal, parotid, or cervical).
Other signs: Anorexia, depression, difficulty swallowing, and guttural pouch infection with pus accumulation (empyema).

Management:

Monitor for symptoms, isolate infected horses, and disinfect shared equipment and environments.
Complicated cases may require antibiotics and veterinary care.

Strangles: Key Points from Fox Run Equine Center

Carrier Horses & Reservoirs:

Carriers:May shed Streptococcus equi bacteria continuously or intermittently for months to years, acting as major reservoirs and causing outbreaks.
Bacterial Location: Often carried in guttural pouches or paranasal sinuses.

Exposure & Isolation:

Incubation Period: 3–14 days post-exposure before fever appears.
Isolation Period: Minimum of 14 days for new arrivals to prevent outbreaks.

Diagnosis:

Culture: From nasal discharge or abscess.
PCR: Detects S. equi DNA.
Serology: Blood test for SeM protein titers.

Treatment:

Antibiotics: IV penicillin preferred; avoid SMZs.
Early Use: May hinder immunity, risking reinfection.
Severe Cases: Require antibiotics, tracheostomy, and support.

Prevention:

Vaccination: Reduces severity but not full prevention.
Intranasal: Best for local IgA immunity; recommended via a veterinarian to avoid complications.

Outbreak Management:

Isolation: Separate affected horses immediately.
Temperature Monitoring: Check twice daily (normal: 99–102°F / 37–38.8°C); isolate at the first fever.
Hygiene: Use separate caretakers and equipment; enforce strict disinfection.
Movement Ban: Halt farm movement for 8 weeks after the last resolved case.

Quarantine & Screening:

Test for carrier horses using blood, guttural pouch, or pharynx samples.
Recovered horses typically gain immunity for up to five years.