An official website of the State of Maryland.

Maryland.gov Translate

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Maryland Department of Agriculture

About equine strangles

Strangles is a highly contagious bacterial disease of the upper respiratory tract in equids. It is caused by Streptococcus equi equi. Strangles is one of the most common infectious diseases of horses worldwide. Transmission occurs via direct contact with infected horses or with contaminated equipment or clothing. 

Strangles is a highly contagious bacterial disease of the upper respiratory tract in equids, caused by Streptococcus equi equi. It is one of the most common infectious diseases of horses worldwide. Transmission occurs via direct contact with infected horses or through contaminated equipment or clothing.

Clinical signs

  • Lethargy
  • Anorexia
  • Fever
  • Swollen lymph nodes with abscess formation and rupture
  • Respiratory obstruction and difficulty swallowing as lymph nodes swell
  • Nasal discharge
  • Soft, nonproductive cough

Prevention & management

The best prevention strategy is to minimize exposure to the bacteria.

  • Quarantine: New horses should ideally be kept separate from your current horses for a minimum of 14 days, ideally 30 days, especially if their health history is unknown.
  • Vaccinate: A vaccination is available—consult your local veterinarian about preventing Strangles in your herd or if you suspect your animals may be infected. Ensure your horses are up-to-date on core and risk-based vaccinations.
  • Isolate sick horses: Sick horses should be isolated immediately. In addition, stop all movement of horses on and off the affected premises immediately.
  • Practice good hygiene: Limit contact from outside horses and people. Use proper hygiene with visitors and shared equipment. Wear gloves when handling sick horses. 
  • Prioritize cleanliness: Ideally, stalls should be cleaned every day and kept as clean as possible.
  • Use insect control, rodent control, weed control, and remove or eliminating standing water.

Reporting requirements

Veterinarians must report cases of strangles to the State Veterinarian within 48 hours of first knowledge of the disease.

What to do if an outbreak occurs

Collect a detailed history

  • Vaccination history
  • Travel history
  • Management practices

Practice cohorting

  1. Create 3 color-coded groups (Even if space is limited, horses that must remain in the same paddock can be separated by 2 layers of electric fence to prevent nose-to-nose contact.):
    1. Red: Horses that have shown 1 or more clinical signs consistent with strangles.
    2. Amber: Horses that have had direct or indirect contact with an infected horse in the red group. Indirect contact includes shared caretakers, water troughs, feed buckets, cleaning equipment, etc.
    3. Green: Horses which have had no known direct or indirect contact with affected animals.
  2. Temperature checks: Green and amber groups should be checked twice daily, and any febrile horses moved to the red group.
  3. Color code equipment: Clearly color code buckets and other equipment to prevent indirect contact between the groups.
  4. Disinfection:
    1. Disinfect all water and feed buckets daily.
    2. Eliminate all sharing of water.
    3. Place foot baths at the entrance of each barn or stall depending on your group setup.
  5. Dedicated staff:
    1. Dedicated staff should be assigned for each color-coded group.
    2. If separate staff is not an option, they should move from the green group, to the amber group, and then to the red group in that order with no backtracking.
    3. Use personal protective equipment (PPE) such as coveralls, boots, and gloves that can be changed or thoroughly disinfected between groups.

Test and follow up

  • Test to see if recovered horses may still be infectious: Test for potential carriers (after 3 weeks of resolution of clinical signs or potential exposure with no clinical signs).
  • Persistent symptoms: If nasal discharge persists longer than 2 weeks, guttural pouch examination is recommended to identify any horses that may need additional treatments.

Common disinfectant tips

The time it takes for a disinfectant to kill germs (contact time) varies by product. Always check the product label for specific instructions.

  • Label instructions: Always refer to the specific product label for accurate contact and dilution instructions.
  • Surface wetness: Ensure the surface remains wet for the entire contact time to allow the disinfectant to work effectively.
  • Material compatibility: Some disinfectants may damage certain materials, so check compatibility.
  • Dilution: Proper dilution is crucial for effectiveness.
  • Removing organic material: In order for any disinfectant to work, the surface has to be free of organic material.