Respiratory case 2 - strangles

Case Introduction

• Patient: Fernie, a 7-year-old Arabian mare

• Recent History: Attended a competition last week and is now exhibiting:

  • Depression

  • Anorexia

  • Nasal discharge (snotty nose)

Differential Diagnosis

• Given the recent contact with other horses and presentation, the most likely cause is infectious respiratory disease. Potential differentials include:

  • Strangles (caused by Streptococcus equi)

  • Equine Influenza

  • Equine Herpesvirus

• Other less probable causes:

  • Equine Arterivirus (notifiable, rarely seen in the UK)

  • Equine Rhinovirus and Equine Adenovirus (uncommon)

• Less likely causes: Sinusitis and dental disease, typically would not present with depression and anorexia.

Clinical Examination

• Vital Signs:

  • Heart Rate (HR): 36 bpm

  • Respiratory Rate (RR): 12 brpm

  • Rectal Temperature: 39.5°C

• Physical Findings:

  • Dull demeanor

  • Right unilateral mucopurulent nasal discharge

  • Bilateral enlarged, hot, and painful submandibular lymph nodes

Diagnostic Testing

• The recommended diagnostic test to perform: Nasopharyngeal swab

  • Rationale: High sensitivity and specificity for infectious respiratory diseases during early infection

  • Preferred due to rapid PCR results available within 24 hours for strangles, flu, and herpes.

Interim Management Strategies

• While awaiting test results, the following management steps are advised:

  • Administer NSAIDs (e.g., flunixin or phenylbutazone, considering meat chain status if using phenylbutazone).

  • Hot packing of submandibular lymph nodes to facilitate drainage.

  • Encourage hydration and nutrition by offering soft, palatable mash feeds.

  • Isolate the horse and implement barrier nursing with minimal caregivers.

  • Communicate disease status with yard personnel and other horse owners.

Diagnosis Confirmation

• Confirmatory testing revealed a positive PCR for strangles.

  • Causative Agent: Streptococcus equi var. equi

Pathogen Transmission

• Routes of Transmission for Strangles:

  • Nose-to-nose contact

  • Faeco-oral transmission

  • Aerosolized droplets

  • Fomites (inanimate objects carrying pathogens)

Biosecurity Measures

• Meeting held with Fernie's owner and the yard manager:

  • Traffic Light System for Biosecurity:

    • Red Group: Isolated suspected/confirmed cases with strict rules to prevent contact.

    • Amber Group: Isolated potentially exposed horses.

    • Green Group: Healthy horses with no known exposure for at least 3 weeks.

• Recommendations for monitoring horses, with rectal temperatures checked twice daily. If pyrexic, horse to be moved to the red group immediately.

Re-opening the Yard

• Following disease resolution, biosecurity measures should remain in place:

  • At least 4 weeks after the last clinical signs before restrictions are relaxed, optimal for negative test results.

  • Suggested testing method: Guttural pouch lavage for PCR and culture due to higher sensitivity for detecting carriers.

Follow-Up Testing and Interpretation

• Post-infection testing protocol:

  • Understanding the results:

    • Serology negative: No recent exposure

    • Serology borderline: Possible recent infection, re-test needed

    • Serology positive: Indicative of carrier state; additional testing required (GP PCR and culture)

• Intermittent Shedding: May require multiple NP swabs for confirmation.

Vaccination Information

• Vaccines available in the UK for strangles:

  • Equilis StrepE: Live vaccine (modified live, intramuscular, 2 doses 4 weeks apart).

  • StrangVac: Live vaccine (submucosal injection in the upper lip).

  • Both vaccines offer protection without interfering with serology testing.