Introduction

• Abnormal respiratory secretions emanating from the upper or lower respiratory tract, eg serous, mucus, pus, blood; also from upper gastrointestinal tract, ie digesta.
• Cause: bacterial, viral, fungal upper or lower respiratory tract infection; neoplasia; trauma; EIPH; RAO; gastrointestinal tract obstruction.
• Signs: unilateral or bilateral discharge containing serous, mucus or purulent material; blood, food, aspirated meconium.
• Diagnosis: endoscopy, radiography, fluid/aspirate analysis.
• Treatment: depends on etiology.
• Prognosis: good to grave depending on cause and duration or primary disease.

Pathogenesis

Etiology

• Aspiration of material as a result of a pharyngeal defect often results in food appearing in the discharge as well as creating a lower respiratory tract disease.
• Congenital defect:
  • Cleft palate         .
  • Neuromuscular disorder of the pharynx   Pharynx: collapse  .
  • Cricopharyngeal-laryngeal dysplasia (4th branchial arch defect)   Pharynx: 4th branchial arch defects     .
  • Sub-epiglottic cyst     .
  • Esophageal disorders (rare).

Adults - discharge with food

• Cleft palate (diagnosis delayed)     .
• Pharyngeal or esophageal dysphagia:
  • Guttural pouch mycosis   Guttural pouch: mycosis  :
  • Botulism   Botulism  .
  • Grass sickness   Grass sickness  .
  • Choke.
  • Acute onset dysphagia due to damage to one or more of the 9th (glossopharyngeal), 10th (vagus) or branches of the 11th (accessory) cranial nerves (that run with the vagus nerve) which together form the pharyngeal plexus.
  • Massive epistaxis due to concurrent damage to other vital structures in the guttural pouch     .
  • Ipsilateral Horner's syndrome   Neurology: Horner's syndrome  or neck pain.
• Gastric reflux associated with colic   Abdomen: pain - adult  .

Epistaxis

• Guttural pouch mycosis.
• EIPH   Lung: EIPH (exercise-induced pulmonary hemorrhage)  .
• Ethmoid hematoma   Ethmoid: hematoma      .
• Trauma:
  • Iatrogenic, eg nasogastric intubation   Gastrointestinal: nasogastric intubation  .
  • Head trauma   Head: fractures  - traumatized sinuses may fill with blood and drain slowly   →   post-traumatic epistaxis (latterly with dark blood) may remain for a month or so.
  • Traumatic rupture of the ventral rectus capitis muscles that lie beneath the base of the skull within the guttural pouches.
• Nasal or sinus mycosis, occasionally primary sinusitis - traces of blood at the ipsilateral nostril accompanied by copious, unilateral purulent and usually malodorous discharge.
• Sino-nasal neoplasia - intermittent, low-grade, ipsilateral epistaxis plus more prominent signs including unilateral purulent nasal discharge, nasal airflow obstruction and facial swelling.

Bilateral discharge - foals - respiratory tract disease

• Neonatal septicemia syndrome   Foal: neonatal septicemia syndrome  .
• Meconium aspiration   Respiratory: meconium aspiration  - bilateral brown nasal discharge and coughing sometimes associated with dystocia and fetal distress   Reproduction: dystocia  .
• Neonatal equine herpes virus Type I   Abortion: EHV-1  ; usually associated with abortion storm   Respiratory: EHV infection  .
• Adenovirus infection   Equine adenovirus infection (EAI)  (in immunocompromised foals).
• Rhodococcuspneumonia   Rhodococcus equi infection  - older foals; coughing and nasal discharge often appear late in infection.

Bilateral discharge - adults - transmissible infectious disease

• Equine influenza   Equine influenza  .
• Equine Herpes Types 4 and 1   Abortion: EHV-1    Respiratory: EHV infection    Equine herpesvirus  (the latter can also cause abortion and/or paraplegia).
• Rhinoviruses   Rhinovirus infection  .
• Adenovirus   Equine adenovirus infection (EAI)  and equine viral arteritis   Equine viral arteritis (EVA)  (the latter can also cause abortion).
• Mycoplasma felisandM. equirhinis  Mycoplasmas and ureaplasmas  .
• Strangles   Strangles (Streptococcus equi infection)  .
• Pasteurella  Pasteurella multocida  .
• Actinobacillus  Glanders  .
• Pneumococcusspp.
• Streptococcus zooepidemicus  Streptococcus spp  .

Adults - other lower respiratory tract disease

• Pleuropneumonia (shipping fever)   Lung: pleuropneumonia - bacterial (pleuritis)  .
• Recurrent airway obstruction (RAO)   Lung: recurrent airway obstruction (RAO)  .
• Summer pasture associated obstructive pulmonary disease (SPAOPD)   Lung: SAD (summer pasture-associated recurrent airway obstruction)  .
• Post-infectious pulmonary disease - prolonged low-grade respiratory signs following an acute respiratory tract infection.
• Aspiration pneumonia.
• Interstitial lung disease - alveolitis and fibrosis of the interstitial pulmonary tissues (   →   restricting lung expansion).
• Lungworm   Lungworm infection   (Parascaris equorumin weanlings andDictyocaulus arnfieldiin adults).
• Foreign bodies.
• Neoplasia   Respiratory: neoplasia  .

Adults - other upper respiratory tract disease

• Rostral (1st-3rd) maxillary cheek teeth abscessation (facial swelling or a facial sinus tract is more common).
• Sinusitis (paranasal sinus empyema).
• Dental sinusitis (infection of apices of 3rd-6th maxillary cheek teeth).
• Primary sinusitis.
• Sinus (maxillary) cyst.
• Sino-nasal neoplasia.
• Nasal foreign bodies.
• Sino-nasal mycosis (mycotic rhinitis).
• Guttural pouch empyema/chondroids or mycosis.

Pathophysiology

• When nasal discharge is present, the normal physiological mechanism for recycling respiratory secretions by swallowing is insufficient.
• Upper respiratory tract inflammation   →   production of excessive secretions plus absence of the usual clearance mechanism, ie loss of the cilia that normally transport secretions caudally towards the nasopharynx for swallowing.
• Lower respiratory tract disease   →   large volumes of secretions are transported from the lower airways by the mucociliary elevator or coughed up into the nasopharynx or nasal cavity (also through the oral cavity).

Serous

• The few drops of bilateral watery discharge present at the nostrils of most normal horses is a serous nasal discharge. This secretion largely emanates from the nasolacrimal duct, ie is composed of tears.

A drop of serous discharge placed between two fingers will not stretch into a "string" if the fingers are separated, indicating a low protein and mucin content.

Mucoid

• Discharge is clear but relatively viscous because it contains high levels of a mucoprotein (mucus), eg as occurs early in a viral respiratory tract infection (usually with upper and lower respiratory tract involvement).
• With a mucoid nasal discharge, the increased volume of nasal discharge contains large amounts of mucin proteins produced in response to inflammation of any part of the specialized respiratory mucosa, from the distal bronchiole up to the nasal cavity.

A drop of mucoid secretions placed between two fingers will stretch out into a string when the fingers are separated.

Mucopurulent

• Composed of mucoid respiratory secretions containing lower amounts of leukocytes, which are usually neutrophils with bacterial infections.
• Neutrophils are also the predominant infiltrate even with uncomplicated viral or fungal respiratory infections, and even with allergic respiratory inflammation.
• The degree of purulence can vary from secretions that are almost mucoid in nature with just a hint of purulence, eg in a recurrent airway obstruction (RAO) case that is in remission following some weeks of environmental control, to secretions with so many leukocytes that they are almost completely purulent.

Purulent

• Very viscous secretions, with the viscosity partly due to their neutrophil DNA content.
• Purulent secretions are opaque, varying from white, yellow to green in color, with their coloration sometimes dependent on the type of bacteria causing the underlying respiratory inflammation. In some cases, purulent respiratory secretions will be malodorous due to the role of anaerobic bacteria in the underlying process.

Do not always associate purulent respiratory secretions with bacterial infections, remember that uncomplicated viral, eg equine influenza, infections can also induce temporary (for a week or so) purulent respiratory secretions. In addition, fungal, eg mycotic rhinitis/sinusitis, infections also induce purulent and often malodorous respiratory secretions. Allergic respiratory tract inflammation seldom induces purulent respiratory secretions, more usually mucopurulent secretions.

Nasal discharge with food

• The presence of food in equine nasal discharge (which is almost always a bilateral nasal discharge) often indicates the presence of pharyngeal or esophageal dysphagia (inability to swallow).
• Sometimes, food material alone may appear at the nostrils.
• In horses with colic, a nasal discharge containing food usually indicates the presence of gastric reflux due to a build up of fluid in the rostral small intestines and stomach, and additionally, due to loss of esophageal tone in cases of equine grass sickness.

Epistaxis

• The presence of blood at the nostrils is most commonly due to exercise-induced pulmonary hemorrhage (EIPH). Being a pulmonary disorder, this should in theory cause a bilateral epistaxis, however because such small volumes of blood (<50 ml) are often present at the nostrils (most of the pulmonary hemorrhage is swallowed), the epistaxis may be unilateral.
• The presence of chronic unilateral epistaxis is most commonly due to unilateral upper respiratory tract lesions such as progressive ethmoid hematoma (PEH) or to traumatic sinus hemorrhage such as caused by a fall or a kick to the head.
• Even though guttural pouch mycosis is invariably unilateral, the high volume of blood lost from the major vessels it contains causes the nasopharynx to fill with blood and thus usually leads to bilateral epistaxis.

Diagnosis

Treatment