Equine Strangles

Question 1

What causes equine strangles? What horses are most commonly affected?

Answer 1

Streptococcus equi –> Gram-positive, beta-hemolytic, Lancefield group C, NOT a normal inhabitant of respiratory tract

young horses (<2-5 y/o) –> highly contagious, herd outbreaks common

Question 2

When does Streptococcus equi (Strangles) typically establish itself within a herd? What is the pathogenesis?

Answer 2

when a new horse is purchased or transferred from another facility without a proper quarantine

• organism is inhaled or ingested after direct contact with purulent discharge from infected horse or contaminated equipment
• organism adheres to epithelial cells of mucosa and is able to replicate within local LNs, thus establishing itself within the pharyngeal region
• infection eventually results in LN abscessation and drainage until the host is able to clear the infection

Question 3

How long is the incubation period of Streptococcus equi (Strangles)? What clinical signs are most common?

Answer 3

2-7 days

• fever, inappetence, lethargy
• serous to mucopurulent nasal discharge
• lymphadenopathy - initially firm and then becomes soft until rupture, can be severe enough to occlude the airway

Question 4

What 3 lymph nodes are most commonly affected by equine Strangles?

Answer 4

1. intermandibular LNs
2. retropharyngeal LNs
3. internal LNs (bastard strangles)

Question 5

How is a definitive diagnosis of equine Strangles reached?

Answer 5

culture of pharynx or purulent discharge

Question 6

What are the 3 methods of when to use antibiotics when treating equine Strangles?

Answer 6

1. signs of strangles without LN abscessation = run natural course or use Penicillin
2. exposure = Penicillin can be used to prevent seeding of LNs
3. abscessation = DON’T use Penicillin as it will slow the progression of disease (can use Penicillin if horse becomes severely depressed, anorectic, or febrile)

Question 7

Other than antibiotics, what supportive treatments are recommended for equine strangles?

Answer 7

• respiratory distress = tracheostomy
• hot packing firm LNs = matures abscess and allows clinician to lance the abscess with a scalpel blade
• NSAIDs = control fever and improve appetite

Question 8

What are 4 possible complications associated with equine strangles?

Answer 8

1. internal abscessation (bastard strangles) - mesenteric +/- other internal LNs develop abscesses –> horses show chronic history of colic, fever, anorexia, and weight loss
2. purpura hemorrhagica - vasculitis results in pitting edema of the limbs and head, petechiation, and intermittent fever or weight loss
3. guttural pouch empyema - purulent material collects in the GP resulting in chronic infection and shedding of the bacteria without overt clinical signs
4. septicemia/encephalitis - poor prognosis

Question 9

What is prognosis of equine strangles like?

Answer 9

good - most horses recover uneventfully

• once they recover immunity to strangles is good, but they will not be completely immune to a second infection later in life