Respiratory Pathology

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Porky
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245652
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Respiratory Pathology
Updated:
2013-11-11 07:00:13
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pathology respiratory
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4 respiratory pathology lectures
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  1. 3 Main Routes of Invasion
    • (1) Aerogenous
    • - >10μm = above larynx

    - as particle size ↓, aerodynamics ↓, so no. of particles that pass down resp. tract ↑

    • - ~1-2μm = bronchiolar-alveolar junction
    •   ↳as total air space ↓, air stream velocity ↓↓, so ↑ time for particles to settle by gravity

    • (2) Haematogenous
    • - caudal lobes
    • (but all lobes affected when challenge high)

    • (3) Transcoelomic
    • - extension from pleura/mediastinum
    • - traumatic penetration (chest wall, diaphragm or oesophagus)
  2. Progressive Ethmoid Haematoma
    • Specific equine entity of nasal cavity
    • Pedunculated mass in ethmoid region
    • May contain haemosiderophages
  3. Epistaxis + Haemoptysis
    • Epistaxis = blood in nasal discharge

    Haemoptysis = blood in saliva or sputum
  4. Sinusitis
    • Sequel or associated with rhinitis
    • Purulent inflammation → chronic (poor drainage) 
    • Caused by:
    • - penetration of infections from dehorning wounds/ fractures of facial bones
    • - dental/periodontal disease
  5. Rhinitis
    • Serous - mildest, early stages, serous cells
    • Catarral - goblet cells (→ hyperplasia) and mucous glands, mucopurulent
    • Purulent - neutrophils
    • Fibrinous - ↑ vascular permeability
    • Granulomatous - macrophage, specific or chronic allergic reaction
  6. Chronic Rhinitis
    • Chronic purulent (impairment of local defences)
    • - fibrosis of lamina propria
    • - atrophy of nasal glands
    • - squamous metapasia

    • Nasal Polyps
    • - polypoid thickening of inflamed nasal mucosa
    • - horses, cats and sheep
  7. Strangles
    (e.g. of bacterial rhinitis)
    • Haemolytic streptococci - S. equi
    • - Suppurative rhinitis
    • - Pharyngitis
    • - Lymphadenitis
    • After 2-3 weeks, LNs rupture and discharge pus
    • Complications:
    • - metastatic abscesses (bastard stangles)
    • - guttural pouch empyema or chondroid formation
    • - purpura haemorrhagica
  8. Chronic Bronchitis
    • Can result in:
    • - excess mucus production (goblet cell hyperplasia)
    • - squamous metaplasia  (affects mucociliary clearance)
    • - bronchiectasis
  9. Squamous Metaplasia
    Replacement of ciliated epithelium by more resistant but relatively non-functional squamous epithelium
  10. Bronchiectasis
    • - permanent saccular or cylindrical dilation of bronchi
    • - as a result of accumulation of exudate within lumen and partial rupture of bronchial walls

    • - sac-like nodules in lungs which are filled with purulent exudate
    • - cattle most prone due to their anatomy/physiology
  11. Bronchiolitis Obliterans
    • When exudate cannot be cleared in bronchiolitis
    • - infiltration of fibroblasts
    • - development of organised polyp-like masses within bronchiolar lumen
  12. Consolidation
    altered texture of lung (firmer) due to accumulation of exudates
  13. Pulmonary Abscesses
    • Caused by:
    • - septic emboli lodging in vessels
    • - extension from severe focal suppurative bronchopneumonia
    • - aspiration pneumonia
    • - direct penetration


    • - multiple, widespread → haematogenous
    • - isolated, cranioventral → suppurative pneumonia
  14. Equine Pnemonias
    • Mild bronchointerstitial pneumonias:
    • - Equine Influenza
    • - Equine viral rhinopneumonitis

    • Severe suppurative bronchopneumonia:
    • - Rhodococcus equi
    •   ↳ survives within alveolar macrophages 
    •   ↳ abscesses → coalesce to large areas of confluent necrosis
  15. Bovine Pneumonias
    • Shipping/Transit Fever:
    • - pasteurellosis (multocida and haemolytica)
    • - stress/viruses etc can cause these normal flora to cause disease
    • Enzootic Pneumonia:
    • - mild bronchointerstitial pneumonia
    • - viruses or mycoplasmas with secondary bacterial infection
    • Tuberculosis:
    • M. tuberculosis + M. bovis
    • - granulomatous inflammation
    • - primary complex: lungs and regional LNs, small tubercles then caseous necrosis
    • - miliary tuberculosis (other organs/tissues)
    • Respiratory Syncytial Virus (RSV):
    • - winter housing
    • - cranioventral atelectasis and consolidation
    • - interstitial emphysema in caudal lung lobes (mast cell degranulation and histamine release)
    • - syncytial giant cells
  16. Canine Pneumonias
    • Parainfluenza virus type 3 (PI3)
    • - initial bronchitis → bronchiolitis → extension into alveoli
    • - neutrophilic exudate
    • Canine distemper virus (CDV)
    • - catharral oculonasal discharge
    • - pharyngitis
    • - bronchitis 
    • - predisposition to secondary bacterial infection
  17. Ovine Pneumonias
    • Maedi Visna Virus
    • - lymphoid interstitial pneumonia
    • - heavy lungs, mottled green/tan colour
    • - enlarged associated LNs
    • - extensive lymphoid proliferation with smooth m hyperplasia
    • Pasteurellosis
    • - e.g. from mastitis or septicaemia
    • - similar to cows
  18. Porcine Pneumonias
    • Porcine Reprodctive and Respiratory Syndrome (PRRS)
    • - transient loss of apetite
    • - slight hyperthermia
    • - respiratory distress
    • - anterior lobe pneumonia
    • Porcine Enzootic Pneumonia
    • - mycoplasma hyopneumoniae
    • - suppurative or catharral bronchopneumonia
    • - confluent consolidation of cranioventral lung lobes
    • Pasteurellosis
    • - severe acute fibrinous pneumonia
    • P. multocida secondary to underlying mycoplasma pneumonia
    •   ↳ chronic suppurative bronchopneumonia with abscessation and pleuritis
  19. Pulmonary Mycoses
    • Aspergillus fumigatus
    • - birds
    • - multiple discrete grey/white nodules around fungal colonies
    • - haemorrhage or thrombosis if BVs involved
    • Pneumocystis carinii
    • - young or immunosuppressed animals (mostly humans)
    • - diffuse interstitial pneumonia
    • - pale staining trophozoite/cysts in alveoli
  20. Atelectasis
    Incomplete expansion of lungs at birth (congenital) or collapse (acquired)

    • - obstructive
    • - compression (LAs sharply demarcated fluid line)
    • - recumbency (hypostatic)
    • - defective surfactant production
  21. Secondary Pulmonary Emphysema
    • Alveolar:
    • distension and rupture of alveolar walls
    • → formation of 'air bubbles' in parenchyma

    • Interstitial:
    • Air in interlobular CT
    • → forms bullae
    • → bullous emphysema
  22. Mechanisms to prevent entry of circulatory fluids into alveolar air spaces
    - alveolar epithelium and junctions highly permeable to fluid and seal off spaces

    - interstitium of alveolar septa is at lower pressure than intra-alveolar pressure

    - interstitial pressure becomes more sub-atmospheric (-ve) toward fascia and hilus

    Net effect = liquid moves from alveolar interstitium towards lymphatics in fascia then hilus of lung and mediastinum
  23. Pulmonary Oedema
    Interstitial oedema → alveolar oedema

    • - ↑ capillary or type I epithelial permeability caused by systemic toxins, shock or inhaled caustic gases
    • - ↑ capillary hydrostatic pressure
    • - ↓ plasma oncotic pressure
  24. Pneumothorax
    • air in pleural cavity
    • atelectasis
  25. Hydrothorax
    oedema fluid in pleural cavity
  26. Chylothorax
    • - chylomicron-rich lymph in pleural cavity
    • - traumatic/inflammatory rupture of thoracic lymphatic duct
  27. Haemothorax
    blood in pleural cavity
  28. Pyothorax
    • "thoracic empyema"
    • purulent effusion in pleural cavity

    • >horses - secondary to pneumonia or abscesses (strep.)
    • >dogs - migrating grass awns (actinomyces)
  29. Pleuritis/Pleuracy
    • - extension from pneumonia
    • - bloodstream
    • - trans-diaphragmatic lymphatics from peritoneal cavity
    • - penetration of chest, oesophagus or abdominal viscus (reticulum)

    • > acute = purulent and fibrinous
    • > chronic = pleural adhesions and organising fibrinous pleuritis

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