Understanding Equine Strangles

Christina L. Garloff, DVM

Equine Veterinary Associates, Inc.

History

First reported in 1251Highly contagious

Young horses most commonly affected

Recurrence at farm commonMost commonly diagnosed contagious disease worldwideCause

Bacterial infection with Streptococcus equi subspecies equi (S. equi)

Location Usually affects the upper airway and lymph nodes of the head & neck,

but can be seen in other portions of the body

Clinical Signs Common:

Fever (> 101.5°F) Anorexia, depression, difficulty swallowing Nasal discharge Enlarged submandibular lymph nodes Purulent nasal discharge

Less common Enlarged retropharyngeal lymph nodes

Guttural pouch infection-Empyema Enlarged lymph nodes on other portions of the head

Complications Most recover without complication Infection in other parts of the body

Metastatic infection or Bastard Strangles Strangulation of airway

Tracheostomy Immune mediated disease

Purpura Hemorrhagica Muscle disease Decreased milk production in mares

Transmission

Nasal/abscess discharge from infected horse Days to weeks

Nasal discharge from asymptomatic carrier Months to years

Contaminated environment Water-over 1 month, ground/bedding variable

Contaminated equipment &/or handlers Buckets, feed tubs, grooming equipment, stall cleaning supplies, tack, clothing, other

animals

Diagnosis

Clinical signs highly suggestive Culture of discharge PCR nasal swab

Start shedding a few days after fever onset Intermittent for several weeks

4-50% of horses on recurrent farms are carriers Months to years

Blood titer-rise in levels when infected

Treatment Antibiotic therapy remains controversial

Needed for complicated cases Anti-inflammatories for pain/fever Hot pack affected area

+/- drawing agent (Ichthammol, etc.) Surgically lance when mature

Soft feed if throat is sore Isolation from other horses!!

Outbreak Management Horse movement in and out of stable should stop Monitor temperatures twice daily Isolate at first sign of fever

Contagious 1-2 days after fever begins

Outbreak Management

Create three separate groups Clean horses with no exposure

Separate area & separate caretakers & equipment Daily care should be first

Exposed horses Infected horses

Outbreak Management Infected horses

Use protective clothing Care for last Use dedicated equipment Thoroughly disinfect equipment

between horses Thoroughly disinfect hands and

shoes between horses Disinfect water buckets daily Waste from infected horses should

be isolated & disposed of separately Rest exposed turn-outs/arenas

minimum of 4 weeks Three consecutive negative PCR

swabs (at least one week apart) for each horse before returning to general population

Vaccination Does not guarantee disease prevention

Intramuscular route High rate of vaccine reactions Approx 60% effective

Intranasal route Current recommended vaccine Initial 2 doses, 2-3 weeks apart-protected 1 month after second

dose, annual booster

Not recommended during an outbreak Recovered horses often develop immunity for 1 year

or more

Preventative Measures Require current health certificates for all new horses Obtain Strangles history/require negative PCR test before allowing on property

Consider vaccination requirement before arrival Quarantine new horses for a minimum of 3 weeks before allowing in general population

Monitor temp daily Each horse should have a dedicated water bucket that is disinfected regularly Minimize exposure to other horses/supplies at shows Pastured horses should be grouped by age & risk level

Questions?