110. Strangles.

Question 1

Occurence of strangles?

Answer 1

Occurrence

• widespread,
• less frequent

Question 2

Aetiology of Strangles?

Answer 2

Aetiology

• S. equi subsp. equi,
• (sometimes S. equi subsp. zooepidemicus – cause milder form)
• Virulence factors:
• hyaluronic acid capsule (shiny colonies),
• EC enzymes (local lesions),
• pyrogen proteins (fever, local lesions),
• M protein (anti-phagocytic effect along with the capsule)

Question 3

Epidemiology of Strangles?

Answer 3

Epidemiology:

• Young (1/2 - 2 years) – younger foals are protected against maternal Abs & older horses have active
• immune reaction so don’t show clinical signs
• Introduction: recovered horses (bacterium carriers, shedding via nasal discharge)
• Found on MM of horses who have survived strangles & remain carriers (not on the MM prior to this)
• Predisposing effects:
• Infectious (viruses)
• non-infectious (dust, cold/humid environment)
• High morbidity (close to 100%)
• Low mortality (<1-2%)

Question 4

Pathogenesis of strangles?

Answer 4

Pathogenesis

• Infection: aerogenic (PO)
• Throat, nasal cavity
• Lymphatic vessels, lymph nodes (of head & neck): purulent inflammation (capsule, M protein, enzymes); abscessation (neutrophils killed & pus formation), fistula, shedding
• Swallowing of pus: necrotic pneumonia
• Sometimes septicaemia: mesentherial LNs (torsion of gut etc.), lungs, joints, brain (abscess)_

Question 5

Clinical signs of Strangles?

Answer 5

Clinical signs

• Typical – atypical – malignant
• Typical form:
• Fever, inappetance (due to inflam. of MM in oropharyngeal cavity so swallowing is painful),
• depression; cough, nasal discharge; throat, nasal cavity purulent inflammation;
• enlarged/swollen LNs (rupture, fistula), difficulties in swallowing, (colic)
• Resp clinical signs due to compressed trachea due to enlarged LNs

Question 6

Diagnosis of strangles?

Answer 6

Diagnosis:

epidemiology - clinical signs; detection of the agent (smear, staining; bacterium isolation; PCR);

detection of antibodies (ELISA – cannot diagnose an acute disease so not enough time for Ab production;

used for detection of previous infection (Abs released against M protein))

Question 7

Treatment of Strangles?

Answer 7

Treatment

• ABs: penicillins, cephalosporins, macrolides
• Surgical treatment, disinfection
• Isolation, rest, elimination of predisposing effects

Question 8

Prevention of strangles?

Answer 8

Prevention:

• prevention of introduction; identification of carriers
• (bacterium isolation: tonsils swabbed – if negative 3x they are not a carrier; PCR);
• vaccines - limited effect
• Focus on prevention of introduction because not normally carried by animals