Equine Upper Respiratory Diseases Quiz

Equine Upper Respiratory Tract Disease

• This presentation covers an approach to equine upper respiratory tract (URT) disease, specifically focusing on various conditions and their presentations.

Learning Objectives

• Understand common conditions affecting the horse's URT.
• Describe diagnostic methods for investigating respiratory conditions in horses.
• Learn about the benefits and methods for different diagnostic modalities.
• Outline the diagnoses, treatments, and control measures for infectious and non-infectious URT diseases.

Outline of URT Conditions

• Bilateral nasal discharge: Includes URT infectious diseases.
• Unilateral nasal discharge: Includes sinus disease, guttural pouch empyema, strangles, and other conditions.
• Epistaxis: Includes trauma, guttural pouch mycosis, and progressive ethmoid hematoma.

Upper Airway Introduction

• Nasal and paranasal regions (rhinitis, sinusitis, nasal cysts, ethmoid haematoma, and nasal/sinus neoplasia).
• Trauma.
• Guttural pouches (tympany, empyema, strangles, mycosis, neoplasia).
• Larynx.
• Lungs.
• Nasal passage.
• Trachea.

Infectious Diseases of URT (Bilateral Nasal Discharge)

• Equine influenza virus (EIV): A common infectious disease of the URT in horses, routine vaccination is helpful for preventing outbreaks.
• Equine herpesvirus (EHV): EHV 4 usually causes respiratory disease in young horses, EHV 1 can cause respiratory disease, neurological disease, late-term abortion, and early foal death.
• Other viral diseases: Equine rhinitis A & B, adenoviruses.
• Strangles: Streptococcus equi subspecies equi, discussed later in the presentation.

Clinical Scenario (Infectious Diseases of URT)

• Risk factors: Horses of all ages, high traffic, large group herds, virus transmission through air, direct nasal droplets, and indirect transmission via people and equipment.
• Clinical presentation: Nasal discharge (often bilateral), enlarged lymph nodes, fever, lethargy (typically transient).
• Consider lower respiratory tract (LRT) disease if accompanied by coughing and tachypnea and possible oesophageal obstruction.

Clinical Scenario (Diagnosis, Treatment & Prevention)

• Diagnosis: Nasal swab for respiratory PCR panel.
• Treatment: Often self-resolving, supportive care includes palatable foods, monitoring hydration levels, and medication (NSAIDs, flunixin meglumine, phenylbutazone). Vaccination is a preventative measure.
• Biosecurity: Limit nose-to-nose contact, and maintain good routine hygiene.

Unilateral Nasal Discharge

• Sinusitis.
• Guttural pouch empyema.
• Strangles.
• Other conditions.

Differential Diagnosis of Unilateral Nasal Discharge

• Sinusitis: Sinus cyst, nasal/paranasal neoplasia.
• Guttural pouch empyema and strangles:.

Paranasal Sinus Anatomy

• The presentation details the different paranasal and conchal sinuses including the frontal, maxillary (rostral and caudal), sphenopalatine, dorsal conchal, middle (ethmoidal) conchal, and ventral conchal sinuses. Illustrations of the anatomy are included.

Aetiology of Sinusitis

• Primary sinusitis: (subacute, chronic) most frequent type (45%).
• Secondary sinusitis:
  • Dental/oral disease (24%).
  • Sinus cyst (13%).
  • Other conditions: trauma, neoplasia, mycosis, ethmoid hematoma.

Pathophysiology of Sinusitis

• Primary sinusitis: URT viral infection, reduced mucociliary clearance, mucus accumulation within sinus, secondary bacterial infection, and accumulation of purulent material (empyema).
• Secondary sinusitis: Obstruction of drainage (trauma, cyst, neoplasia), associated with dental disease.

Secondary Sinusitis: Dental Disease

• Primary dental diseases extending into the sinus (maxillary molars 9, 10, 11).
• Involves the fine alveolar bone layer and sinus periosteum.
• Apical tooth root infections can lead to sinusitis.
• Oromaxillary fistula.

Secondary Sinusitis: Sinus Cysts

• Unknown etiology.
• Benign but expansile, occurring at any age.
• These cysts can distort the paranasal structures.

Clinical Presentation (Sinusitis)

• Serous, mucoid, or purulent unilateral nasal discharge.
• Facial swelling or distortion (maxillary or frontal).
• Nasal airflow obstruction (abnormal respiratory noise).
• Difficulty chewing (dental issues).

Diagnosis (Sinusitis)

• Physical examination (facial symmetry, sinus percussion).
• Oral examination.
• Imaging (radiography, endoscopy: URT, sinus, CT).

Treatments (Sinusitis)

• Aims to remove infection, restore normal drainage and mucociliary clearance, and prevent recurrence.
• Treatments include broad-spectrum antibiotics, mucolytics, sinus trephination, repeat lavage, the removal of the inciting cause.
• Sinus trephination and lavage.
• Sinus flap surgery (better access, standing surgery, and removal of cysts).

2. Guttural Pouch Empyema

• Definition: Exudate accumulation within the guttural pouch.
• Usually a consequence of URT infections (similar to sinus infections).
• Common causative agents include Streptococcus zooepidemicus (a common opportunistic infection), and Streptococcus equi equi (strangles – highly contagious).

Clinical Signs (Guttural Pouch Empyema)

• Fever and related symptoms (anorexia, lethargy).
• Lymph node swelling.
• Unilateral or bilateral purulent discharge.
• Chronic empyema can lead to chondroid formation.

Treatments (Non-Streptococcus equi equi Related Empyema)

• Supportive therapy (NSAIDs, palatable feed).
• Lavage of material (via endoscopy).
• Removal of chondroids (via endoscopy or surgery).

3. Strangles (Streptococcus equi equi Infection)

• Gram-positive, B-haemolytic streptococcus, Lancefield group C.
• Highly contagious URT condition in equids.
• Moderate mortality but substantial morbidity.
• Very significant from an economic and social viewpoint within the equine industry.

Clinical Signs (Strangles)

• Initial fever followed by inappetence, dullness, lethargy, and a second fever.
• URT obstruction, dysphagia, and discharge.
• Systemic bacteraemia, seeding in distant lymph tissue, guttural pouch empyema, and abscess formation.

Clinical Presentation (Strangles)

• Varying severity (more severe in young, old, or immunocompromised horses).
• Mild case: pyrexia followed by pharyngitis and subsequent abscess formation in submandibular and retropharyngeal lymph nodes.
• Severe case: swollen lymph nodes interfering with breathing and swallowing.
• Strangles-related conditions: metastatic infection ("Bastard strangles"), and immune-mediated conditions like purpura haemorrhagica and myositis.

Diagnosis strangles

• Nasal swab (not useful early)
• Nasopharyngeal and GP swab (more effective as abscesses form)
• GP wash (best early diagnosis)
• Bacterial culture
• Molecular diagnosis (qPCR)
• Serology: SEM ELISA, Combined Antigen A & CELISA*

Treatments (Strangles)

• Symptomatic and supportive therapy (NSAIDs, palatable food).
• Drainage of abscesses via hot packs, surgical lancing, daily cleaning/lavage.
• Use of antibiotics judiciously in acute cases.

Strangles Related Conditions

• "Bastard Strangles": hematogenous or lymphatic spread of infection, resulting in metastatic abscesses in the brain, abdomen, mammary glands, and eyes..
• Immune-mediated conditions: necrotizing vasculitis, edema, petechial hemorrhage, petechia on mucous membranes, peripheral oedema, history of exposure to S. equi, and suggestive clinical signs.

Biosecurity (Strangles)

• Highly contagious spread among equine families via nasal discharge, contaminated water, and equipment.
• Shedding of S. equi equi usually ceases 2-3 weeks after clinical signs resolve.
• Silent horse carriers harboring infection in guttural pouches also need detection and treatment.

Biosecurity detection of Strangles

• Isolate horses experiencing relevant clinical signs.
• Using nasopharyngeal and guttural pouch washes/abscess sampling for bacterial culture and PCR.

Biosecurity segregation

• Positive horses should be strictly isolated.
• In-contact horses should be monitored, and tested if suspicious.
• Naive horses should be monitored and tested if suspicious.

Biosecurity – treatment of horse carriers with strangles

• Carrier animals show recovery from recent infections but are still capable of silently carrying the infection.
• Use guttural pouch infusions, tests and releases (e.g penicillin gel).

1. Epistaxis (Nosebleeds)

• Main differentials: Trauma, Ethmoidal hematoma, Guttural pouch mycosis, Exercise induced pulmonary hemorrhage (EIPH)
• Severity: Mild/temporary, intermittent, or life-threatening

Approach to Epistaxis: Trauma

• Trauma to the head/nose, potentially from nasogastric intubation is a common cause
• Trauma to the ethmoid bone → pass the tube ventromedially!
• Treatments often self-limiting, use of supportive care, general approach to blood loss

Approach to Epistaxis: General Approach to Blood Loss

• Blood loss evaluation: PCV, heart rate, CRT, BP, mentation, and other supporting information is assessed to determine seriousness.
• Blood loss estimation in liters (L).
• Considerations of blood transfusion and cross-matching when PCV is lower than 12%.

2. Progressive Ethmoidal Haematoma (PEH)

• Progressive sub-mucosal haemorrhage of ethmoid bone.
• Condition unique to horses, often associated with nasal cavity, sinuses, and/or ethmoid bones.
• Clinical signs include intermittent epistaxis ("mucky" blood).
• Treatment methods vary by lesion size (e.g., formalin for small lesions, surgical resection/ sinus flap for large lesions).

3. Guttural Pouch Mycosis

• Fungal infection, most commonly with Aspergillus fumigatus or Emericella nidulans.
• Opportunistic infection, worsened by climate factors.
• Disease severity varies with location from asymptomatic to epistaxis, and more severe resulting in chronic neurological deficit, hypovolemic shock, and other symptoms.

Diagnosis (Guttural Pouch Mycosis)

• Suggestive clinical signs (recurring epistaxis).
• Endoscopy, to stabilize the horse prior to imaging.

Treatments (Guttural Pouch Mycosis)

• Medical management (anti-fungals, topical infusion).
• Surgical options (blockage of blood supply via catheter/ surgical excision, or coil embolisation).