Diseases and Disorders of the Lower Respiratory Tract

Lectures 40 and 41

What condition is defined as the naturally occurring respiratory disease characterized by periods of reversible airway obstruction caused by neutrophil accumulation, mucus production, and bronchospasm?

severe equine asthma (chronic obstructive pulmonary disease, heaves, recurrent airway obstruction)

What clinical signs can be associated with severe equine asthma?

cough with or without nasal discharge

various degrees of expiratory dyspnea

nasal flare and abdominal push

normal or elevated resp rate, exercise intolerance

severe cases may see weight loss, hypertrophy of external oblique and rectus abominis, pulmonary hypertension, obvious wheezing and severe distress

What are the two forms of severe equine asthma?

recurrent airway obstruction

summer pasture associated obstructive pulmonary disease

What are the 3 main events that make up the pathophysiology of severe equine asthma?

airway obstruction / bronchoconstriction

airway inflammation

mucus accumulation

How can we diagnose severe equine asthma?

history and physical exam

endoscopy

respiratory samples via tracheal wash and BALF —> BALF is preferred, >15% neutrophils indicates SEA

How can we treat severe equine asthma?

environmental control —> eliminate the trigger, reduce dust

medical treatment —> corticosteroids, bronchodilators, mucolytics (acetylcysteine)

What condition is characterized by poor performance, exercise intolerance or coughing with or without excess tracheal mucus, non septic LRT inflammation detected on BALF cytology, and pulmonary dysfunction?

mild equine asthma

Which condition is described: SEA or MEA?

• older horse

• elevated resp rate, dyspnea

• broncho interstitial pattern on radiographs

• elevated neutrophils on BALF cytology

• good response to environmental control

severe equine asthma (SEA)

Which condition is described: SEA or MEA?

• all ages

• resp rate normal, no dyspnea

• no changes on radiography

• elevated neutrophils, eosinophils, and mast cells on BALF cytology

• variable response to environmental control

mild equine asthma (MEA)

What clinical signs can be associated with mild equine asthma?

poor performance

difficult recovery after exercise

accumulation of mucus

cough, nasal discharge

no dyspnea

no systemic signs

no CBC abnormalities

no clin path abnormalities

How can we diagnose mild equine asthma?

history and physical exam

tracheo-bronchial endoscopy reveals mucus and hyperreactivity

BALF cytology showing elevations of neutrophils, eosinophils, and mast cells

How can we treat mild equine asthma?

environmental control

medical treatment with corticosteroids, bronchodilators, omega 3 fatty acids, sodium cromoglycate, acetylcystein, antibacterials

What is the etiology of exercise induced pulmonary hemorrhage (EIPH)?

alveolo-capillary membrane rupture due to stress across the alveolo-capillary membrane resulting from exercise

What risk factors are associated with exercise induced pulmonary hemorrhage (EIPH)?

pulmonary capillary hypertension

rheological properties of blood

subatmospheric pleural pressure

extra-thoracic airway obstruction

intra-thoracic airway obstruction

IAD - mild equine asthma

coagulopathy

bronchial neovascularization

pulmonary fibrosis, altered compliance

locomotor forces

True or false: The more intense the exercise the greater the proportion of horses with exercise induced pulmonary hemorrhage (EIPH).

True

What clinical signs can be seen in cases of exercise induced pulmonary hemorrhage?

may be none

bilateral epistaxis

poor performance may be due to other problems and is difficult to assess

How can we diagnose exercise induced pulmonary hemorrhage?

history and physical exam

endoscopy before and after exercise (graded 1-4 based on severity)

cytology of respiratory samples from tracheal wash or BALF is more sensitive than endoscopy

pulmonary radiographs are of limited use

List differentials for hemorrhage into the trachea/bronchi (LRT).

EIPH

pulmonary abscess

trauma

pneumonia

pulmonary foreign body

pulmonary neoplasia

List differentials for epistaxis.

EIPH

pulmonary abscess

trauma

pnuemonia

pulmonary foreign body

neoplasia

guttural pouch mycosis

progressive ethmoidal hematoma

thrombocytopenia

How can we treat exercise induced pulmonary hemorrhage?

prevent stress rupture of capillaries by decreasing pressure in pulmonary capillaries or increasing alveolar inspiratory pressure

decrease inflammation and angiogenesis

reduce bleeding (check coagulopathy, platelet function)

maintain capillary integrity

How can we decrease pressure in pulmonary capillaries to treat EIPH?

furosemide

How can we increase alveolar inspiratory pressure to treat EIPH?

in URT, correct dynamic collapse and use “flair” strips

in LRT, administer bronchodilators, corticosteroids, and reduce environmental dust

What is the most common pathogen causing pneumonia in adult horses?

Streptococcus equi subsp zooepidemicus (gram positive, beta hemolytic streptococcus)

What type of pathogens create a less favorable prognosis in cases of adult pneumonia?

anaerobes

What are risk factors for adult pnuemonia?

essentially weakened immune system or massive number of bacteria

younger racehorses

prolonged transportation

general anesthesia, upper airway surgery

recent viral respiratory disease

aspiration after choke (obstructed esophagus)

What posture is essential for muco-ciliary clearance in horses?

lowered head

What may be the single most predisposing factor for development of penumonia associated with long distance transport?

head restraint

Describe the pathophysiology of pneumonia in adult horses.

infiltration with inflammatory cells —> damage to epithelium and endothelium —> flooding with inflammatory cells, debris, fibrin —> exudative pleuropneumonia —> fibropurulent pleuropneumonia —> fibrin deposits —> organizational stage (pleural peel)

What clinical signs can be associated with adult pneumonia?

exercise intolerance, cough, nasal discharge

fever, anorexia, depression

tahcypnea, dyspnea, shallow breathing

change in aspect of nasal discharge

pleurodynia

sternal edema

changes in pulmonary auscultation/percussion —> decreased breath sounds in lower lung, muffled sounds on percussion

endotoxemia

How can we diagnose adult pneumonia?

hematology and biochemistry show inflammatory changes

endoscopy

respiratory samples via trans tracheal wash

ultrasound of peripheral lung and pleura reveals fibrin tags

radiographs

thoracocentesis

thorascopy

How can we treat pnuemonia in adult horses?

systemic antimicrobial therapy with penicillin, gentamicin, or metronidazole for at least 10 days

pleural drainage if in respiratory distress, emphysema, odor, or sepsis present

ancillary treatments with NSAIDs or analgesics, hydration, nutrition, oxygenation

What complications can be seen in treatmet of adult pneumonia?

phlebitis, thrombosis, diarrhea

pneumothorax, cellulitis, endotoxemia, laminitis

abscess

What prognosis is associated with adult pneumonia cases?

90% survive, 60% return to athletic function

lower if hemorrhagic necrotizing pneumonia occurs

What is the most common cause of pneumonia in foals <6 months of age?

Rhodococcus equi

True or False: Rhodococcus is zoonotic for those that are immunocompromised.

True

What is the primary route of infection for Rhodococcus in foals?

inhalation

What is the secondary route of infection for Rhodococcus in foals?

ingestion

What clinical signs can be seen in cases of foal pneumonia caused by Rhodococcus?

slowly progressive

mild fever, occasional cough, elevated resp rate

decreased appetite, lethargy

cough, tachypnea, dyspnea

acute respiratory distress, death

chronic suppurative bronchopneumonia (snowstorm in lung appearance)

extensive pulmonary abscessation

How can we diagnose foal pneumonia caused by Rhodococcus?

history, physical exam

hematology and biochemistry show hyperfibrinogenemia, SAA, neutrophilic leukocytosis

radiographs show alveolar pattern, ill defined regional consolidation

ultrasound has irregularities and focal areas of consolidation

trans tracheal wash with PCR and C/S

Nodular lung lesions and mediastinal lymphadenopathy in 1-4 month old foals is highly suggestive of what?

Rhodococcus

Trans tracheal wash PCR and C/S for Rhodococcus suspicion should always be interpreted with what?

clinical signs of LRT disease

cytologic evidence of septic airway inflammation

radiographic or ultrasound eidence of bronchopneumonia

How can we treat Rhodococcus pneumonia in foals?

address respiratory distress

antibiotics —> macrolide (erythromycin, azithromycin, or clarithromycin) + rifampin

ancillary therapies —> nutrition, hydration, environment, oxygenation, NSAIDs

What adverse effects can be seen during treatment of Rhodococcus pneumonia in foals?

diarrhea

hyperthermia, tachypnea

entercolitis in mares (coprophagia)

Treatment of Rhodococcus pneumonia in foals is guided by what?

resolution of clinical signs

normalization of fibrinogen

resolution of ultrasound and radiographic lesions

How can we control and prevent Rhodococcus pneumonia in foals?

management of ventilation, dust, density, isolation, and pasture contamination

screening for clinical signs

passive immunization with hyperimmune plasma

List causes of pneumonia in foals <1 month of age.

hematogenic infection/sepsis

descending lung infection

iatrogenic aspiration

in utero infection

List causes of pneumonia in foals 1-6 months of age.

Strep equi spp zooepidemicus

R. equi

Which rare opportunistic fungi results in concurrent immunodeficiency leading to SCID in arabian foals?

pneumocystis jiroveci (carnii)