8.2.2: Strangles

Question 1

Causative agent of strangles

Answer 1

Strep equi var equi

Question 2

How is strangles transmitted?

Answer 2

• Fomites
• Direct contact
• Contaminated surfaces etc.

Question 3

Clinical signs of strangles

Answer 3

• Sudden pyrexia 48hrs pre-shedding -> important in management of outbreaks
• Mucopurulent nasal discharge
• Retropharyngeal and submandibular LN abscessation
• Pharyngitis: nasal discharge, dysphagia, cough, laryngeal-associated pain, extended head position

Question 4

When does lymph node abscessation happen in strangles and which lymph nodes are most commonly affected?

Answer 4

Occurs 3-14 days after infection
Most common LNs:
1. Retropharyngeal - these commonly rupture into the guttural pouches
2. Submandibular
3. Parotid
4. Cranial cervical

Question 5

Answer 5

Moderate lymphoid hyperplasia (seen with strangles)

Question 6

Answer 6

Guttural pouch empyema
The retropharyngeal lymph nodes rupture into the guttural pouches, filling the pouches with mucopurulent fluid.

Question 7

Complications of strangles

Answer 7

• Pneumonia: bronchopleural fistula ends up leading to pneumothorax
• Distant abscesses due to lymphatic or haematogenous spread
• Development of severe dyspnoea -> may require tracheostomy
• Uncommon: purpura haemorrhagica, immune-mediated myositis, myocarditis are all possible

Question 8

Purpura haemorrhagica

Answer 8

Type III hypersensitivity reaction that occurs weeks after infection

Question 9

Diagnostic testing for acute strangles

Answer 9

• Optimal test = qPCR of nasopharyngeal lavage, followed by nasopharyngeal swabbing, then nasal swabbing
• Culture (34-45% sensitivity, very specific)

Question 10

Diagnostic testing for persistent infection with strangles

Answer 10

• qPCR of endoscopic guttural pouch lavage x3 (7 days apart) = best
• Could do culture - this is very specific but has many false negatives.

Question 11

How could you screen for animals that have been exposed to strangles?

Answer 11

• Dual target ELISA -> use this to screen for exposed animals
• This can help you select animals for guttural pouch lavage qPCR testing

Question 12

When in a strangles outbreak should you begin to search for animals in the carrier state?

Answer 12

• Search for horses in carrier state 3-4 weeks after the last case in the outbreak was identified
• Any time before this is too early!

Question 13

Treatment of strangles

Answer 13

• NSAIDs to manage pyrexia and pain
• Soft, palatable, calorific diet for anorexia/dysphagia
• Abscess management: hot packing, surgical drainage and lavage only once completely matured otherwise will result in incomplete drainage
• Isolation
• Nursing care

Question 14

Treatment of the complications of strangles

Answer 14

• Guttural pouch lavage
• Antibiotics are controversial - not enough evidence to prove they prevent LN abscessation
• Treat persistently infected animals with benzylpenicillin reverse thermodynamic gel
• Give antibiotics to horses with severe dyspnoea, dysphagia, or persistent high fever - controversial
• Abscess drainage and lavage
• Other treatment according to specific complication

Question 15

This is a latero-lateral view of the caudal part of the head. What is circled?

Answer 15

Guttural pouch
* Should be translucent
* Is in part radiopaque due to enlarged retropharyngeal LN bulging into the base of the guttural pouch

Question 16

This is a latero-lateral view of the head. What abnormal findings are present?

Answer 16

Guttural pouch with chondroids
* Pus within the guttural pouches was not evacuated; remained, dessicated and formed chondroids
* These contain visible bacteria within them
* Bacteria can survive in here for a very long time
* Must remove chondroids to clear the infection and then treat

Question 17

This is a latero-lateral view of the head. What abnormal findings are highlighted?

Answer 17

Visible fluid line within the guttural pouch
This is due to the presence of pus in the guttural pouch