Lecture 41: Diseases and Disorders of the Lower Respiratory Tract 2

exercise induced pulmonary hemorrhage

• alveolo-capillary membrane rupture

• source of blood → pulmonary circulation

• exercise → pulmonary artery 20mmHg → 90mmHg

• exercise → pleural -5mmHg → -60mmHg

EIPH risk factors

• pulmonary capillary hypertension

• rheological properties of blood

• subatmospheric pleural pressure

EIPH epidemiology

• distribution is worldwide

• disorder of horses that run at high speed

• the more intense the exercise the greater the proportion of horses with EIPH

EIPH clinical signs

• there may be none

• epistaxis (bilateral)

• poor performance

EIPH endoscopy

• 30-120 minutes after intense exercise (up to 7days)

• EIPH grades 1-4

EIPH cytology of respiratory samples

• more sensitive than endoscopy

• collect BALF on specific side

• RBC and erythrophages (>1 week)

• hemosiderophages (>21 days)

EIPH pulmonary radiographs

• limited use

• dorso-caudal opacification possible

• evaluate other tissues like secondary pneumonia

EIPH treatment

• prevent stress rupture of capillaries → decrease pressure in capillaries, increase alveolar inspiratory pressure

• decrease inflammation and angiogenesis

• reduce bleeding

• maintain capillary integrity

what can be used to decrease pressure in pulmonary capillaries for EIPH?

furosemide

how can alveolar inspiratory pressure be increased for EIPH?

• URT → correct dynamic collapse, flair strips

• LRT → bronchodilators, corticosteroids, reduce environmental dust

EIPH prognosis

• effect on career

• severe episodes associated with poor performance

• 1 episode EIPH → more episodes

bacterial disease of the LRT

• airways → bacterial bronchitis, septic IAD

• parenchyma → pneumonia

• extension → bronchopneumonia, pleuropneumonia

pneumonia etiology

gram-positive beta hemolytic streptococcus → strep equi subsp. zooepidemicus

pneumonia epidemiology

• any age or breed

• younger racehorses

• prolonged transportation

• general anesthesia, upper airway surgery

• recent viral respiratory disease

• aspiration after choke

pneumonia pathophysiology

• weakened immune defenses → stress, viral infection, malnutrition, exposure to dust, general anesthesia, exercise

• massive number of bacteria → dysphagia, esophageal obstruction, confinement with head elevated, transportation, high intensity exercise

what is essential for muco-ciliary clearance in horses?

lowered head posture

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

head restraint

pneumonia clinical signs

• exercise intolerance, cough, nasal discharge

• fever, anorexia, depression

• tachypnea, dyspnea, shallow breathing

• change in aspect of nasal discharge

• pleurodynia

• sternal edema

• changes in pulmonary auscultation/percussion

• endotoxemia

pneumonia diagnosis

• hematology and biochemistry → inflammation

• endoscopy → secretions, location

• respiratory samples → TTW

• ultrasound, radiography

• thoracocentesis

• thoracoscopy

pneumonia treatment

• antimicrobial therapy → penicillin, gentamycin, metronidazole, systemic, aerosolized

• pleural drainage

• ancillary treatments

• complications

pleural drainage for pneumonia treatment

• small amounts of fluid resorb

• indications → volume can cause resp distress, emphysematous, fetid odor, evidence of sepsis

• do it early guided by ultrasound

prognosis of pneumonia

• 90% survival, 60% athletic performance

• low if hemorrhagic necrotizing pneumonia

rhodococcus

• bacterium → gram + facultative intracellular bacterium, ubiquitous

• farm → sporadic or endemic

• zoonosis for immunocompromised

foal rhodococcus

• infection in 1st few days of life

• primary route is inhalation, secondary is ingestion

rhodococcus clinical signs

• slowly progressive

• pulmonary disease

• mild fever, cough

• decreased appetite, lethargy, fever

• chronic suppurative bronchopneumonia

• extensive pulmonary abscessation

rhodococcus diagnosis

• difficult early diagnosis → slow progression, slow functional compensation

• history and PE

• hematology and biochemistry → hyperfibrinogenemia, SAA, neutrophilic leukocytosis

• radiographs → alveolar pattern

what in 1-4 month old foals is highly suggestive of rhodococcus?

nodular lung lesions and mediastinal lymphadenopathy

always interpret TTW for rhodococcus in conjunction with

• clinical signs of LRT disease

• cytologic evidence of septic airway inflammation

• radiographic or u/s evidence of bronchopneumonia

rhodococcus treatment

• address respiratory distres

• AB → macrolides and rifampin

• erythromycin adverse effects include hyperthermia, diarrhea

• synergistic → decreased likelihood of resistance

ancillary therapies for rhodococcus treatment

• nutrition, hydration, environment, oxygenation, NSAIDs

• guided by resolution of clinical signs, normalizations of fibrinogen, resolution of u/s and radiographic lesions

• adverse effects → diarrhea, hyperthermia, tachypnea, enterocolitis in mares (clostridium difficile)

• prognosis is 70-90% survival

rhodococcus control and prevention

• management → ventilation, dust, density, isolation, address pasture contamination

• screening → visual inspection, labs, imaging

• passive immunization → hyperimmune plasma

• gallium

• antimicrobials

pneumonia in neonates

• hematogenic

• descending lung infection

• iatrogenic aspiration

• in utero infection

pneumonia in older foals

• strep equi spp zooepidemicus

• R. equi

interstitial pneumonia

• acute severe interstitial

• sporadic rapidly progressive

• 1-6 months

• form of ALI/ARDS

pneumocystis jiroveci

• rare opportunistic fungal

• concurrent immunodeficiency

• SCID in arab foals