Difference between revisions of "Respiratory Bacterial Infections - Pathology"

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===Enzootic pneumonia of calves===
+
===[[Enzootic Pneumonia - Calves]]===
[[Image:Acute suppurative pneumonia.jpg|right|thumb|100px|<small><center>Acute suppurative pneumonia (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
[[Image:Calf pneumonia.jpg|right|thumb|100px|<small><center>Calf pneumonia - chronic, with abscesses, fibrosis (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
 
  
*Range of infectious agents together with managemental and environmental stress cause damage to the respiratory tract
 
*Causes unthriftiness in animals < 6 months old
 
*Usually the primary pathogen is a virus, secondary pathogens are bacteria and mycoplasmas
 
*Pathogens:
 
**[[:Category:Mycoplasmas|''Mycoplasmas'']]
 
***Mycoplasmal [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]] and [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|pneumonia]] of calves is an important component of the syndrome of enzootic pneumonia
 
***On its own causes Mycoplasmal ("Cuffing") pneumonia responsible for [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis and bronchiolitis]] and [[Lungs Inflammatory - Pathology#Infectious causes of pneumonia|bronchointerstitial pneumonia]]
 
***It is thought to pick up host antigens in order to prevent recognition by the body defences as foreign
 
***In uncomplicated mycoplasma infection, the lesions are generally mild and consist of patchy red/purple areas of [[Lungs Ventilation - Pathology#Atelectasis|atelectasis]] in the '''cranio-ventral lung lobes'''
 
***More confluent areas can develop with an underlying bronchointestitial pneumonia and resulting atelectasis
 
***''M. bovis''
 
****Most pathogenic
 
****Widespread lymphofollicular accumulations which contain germinal centres develop more slowly
 
****These lesions can result in narrowing of the bronchiolar lumina - this is the classical lesion of '''‘cuffing pneumonia’'''
 
***''M. dispar''
 
***''Ureaplasma'' sp.
 
**Viruses
 
***[[Respiratory Viral Infections - Pathology#Respiratory syncytial virus|Bovine respiratory syncytial virus (BRSV)]] - can be primary, causes suppression of pulmonary immune response
 
***[[Respiratory Viral Infections - Pathology#Parainfluenza- 3|Parainfluenza- 3 (PI3)]] - can be primary, causes suppression of pulmonary immune response
 
***[[Flaviviridae|Bovine viral diarrhoea virus (BVDV)]] - suppression of pulmonary immune response
 
***[[Adenoviridae|Adenoviruses]]
 
***[[Coronaviridae|Calf coronavirus]]
 
***[[Respiratory Viral Infections - Pathology#Infectious bovine rhinotracheitis (IBR)|Bovine herpes viruses]]
 
**Bacteria
 
***[[Mannheimia haemolytica|''Manheimia (Pasteurella) haemolytica'' serotype A1]]
 
***[[Pasteurella multocida|''Pasteurella multocida'']]
 
***[[Arcanobacter pyogenes|''Arcanobacter pyogenes'']]
 
***''[[Haemophilus somnus]]''
 
*All transmitted by aerosol and direct contact
 
*Gross pathology:
 
**Consolidation of the cranioventral areas which increases in volume with duration
 
**On cut surface, exudate in the main airway of affected lobules with thickening of the surrounding connective tissue
 
*Micro pathology:
 
**Substantial lymphoid tissue around the airways
 
**Even to proper follicle formation, some of which may be large enough to compress the lumen
 
**Mixed cell exudate in the airway lumen
 
**Partial alveolar collapse distal to the compression
 
**Alveolar exudate contains a mixture of inflammatory cells
 
**Slight thickening of the alveolar walls with lymphocytes
 
  
 
===Acute exudative pneumonia===  
 
===Acute exudative pneumonia===  

Revision as of 14:07, 30 June 2010


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RESPIRATORY SYSTEM INFLAMMATION



In general

  • Main clinical expression is as secondary invaders of previously damaged lung tissue due to viral or parasitic involvement or environmental stress
  • Some are initial pathogens in their own right while others can damage the tract allowing invasion by more pathogenic types

In Dogs

Infectious Canine Tracheitis

Tuberculosis - Dogs

Nocardiosis

In Cats

Chlamydiosis, Feline

Mycoplasma felis

In Horses

Strangles

Streptococcus equi subsp. zooepidemicus

Glanders

Rhodococcus equi

In Cattle

Necrotic Laryngitis

Cillia-associated Respiratory Bacillus

Pneumonic Pasteurellosis

Tuberculosis - Cattle

Contagious Bovine Pleuropneumonia

Enzootic Pneumonia - Calves

Acute exudative pneumonia

In Sheep

Laryngeal chondritis

Oedema and chondritis in larynx of sheep (Image sourced from Bristol Biomed Image Archive with permission)

CAR bacillus

Enzootic pneumonia of lambs

  • Caused by Pasteurella (Manheimia) haemolytica, possibly together with Mycoplasma ovipneumoniae
  • Mainly in late spring/early summer after environmental stress i.e. handling or moving
  • May be acute with producing a fibrinonecrotic bronchopneumonia and associated pleuritis
  • Or tending towards chronicity with abscessation and fibrous pleural adhesions
  • A septicaemic form (mortality 5%) is reported to follow the stress of movement to new pasture in the autumn in weaned lambs.
  • Foci of necrosis containing many bacteria are seen at the site of initial invasion in the pharynx and in the liver
  • Meningitis in young lambs and mastitis in ewes are other expressions

Melioidosis (Pseudoglanders)

  • Caused by Pseudomonas (Malleomyces) pseudomallei, Closely related to P. mallei in horses
  • Causes disease in sheep, goats and pigs, occasionally other species
  • Starts as a pyemia and localises in varius tissues, including the lung as abscessation
    • Encapsulated abscesses contain yellow, caseous or creamy pus
  • Pneumonia and arthritis are the most common presentation

In Pigs

Atrophic Rhinitis

Severe atrophic rhinitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Atrophy of nasal turbinates and distortion and shortening of the snout
  • Caused by co-infection of the nasal mucosa with
    • Bordetella bronchiseptica
      • Appears to facilitate colonisation of nasal epithelium by the toxigenic Pasteurella
    • Toxin-producing strain of Pasteurella multocida capsular type D (or sometimes A)
      • Experimental evidence shows that the toxin acts directly on bone cells of the nasal turbinates to cause bone loss, each pathogen can cause atrophy itself but greater damage when together
  • Exacerbated by adverse dietary and managemental factors
  • In rapidly growing young pigs (4-12 weeks old)
  • Clinical signs
    • Progressive facial deformity with rhinitis, catarrhal nasal discharge
    • Sneezing, coughing, can progress to dyspnoea and anorexia
  • Gross pathology
    • Overlying skin on shortened snout is thrown into folds
    • Deviation of the snout to most affected side
    • Various loss of turbinate bone, ventral usually more affected
    • Deviation of nasal septum away from affected chamber
    • Inflammatory, haemorrhagic and ulcerative lesions in the nasal mucosa
  • Micro pathology
    • Reduction in the amount of bone in the turbinates
    • No osteoid laid down between osteoblasts and existing bone
    • Increased fibrous tissue
    • Non-specific mucosal inflammation
  • 2 forms of the disease
    • 'Progressive' atrophic rhinitis
      • Due to infection of the nasal turbinates by P.multocida strains carrying the toxA gene that encodes for an osteolytic toxin. P.multocida adheres poorly to mucous membranes, and therefore requires a predisposing nasal insult to assist colonisation eg: co-infection with B.bronchiseptica or Porcine cytomegalovirus (inclusion body rhinitis)
      • Turbinate bone atrophy is permanent and progressive
    • 'Non-progressive' atrophic rhinitis
      • Due to infection of the nasal turbinates by Bordetella bronchiseptica strains alone, that carry a gene that encodes for a dermonecrotic toxin.
      • Turbinate bone can regenerate by the time of slaughter

Necrotic laryngitis in pigs

Enzootic pneumonia of pigs

Enzootic pneumonia of pigs(Image sourced from Bristol Biomed Image Archive with permission)
  • Caused by Mycoplasma hyopneumoniae and Mycoplasma hyorhinis
  • Also called mycoplasmal pneumonia
  • Major cause of unthriftiness in young pigs
  • Pneumonia in weaned pigs
  • Cough, reduced growth rate
  • Attached to cilia - no mucociliary clearance
  • Usually non-fatal unless there is secondary infection (e.g. Pasteurella multocida)
  • Gross pathology:
    • Confluent consolidation of the cranioventral lung lobes
    • In other areas there may be small red to grey focal lesions evident which indicate the bronchiolar orientation of the inflammatory process
  • Histologically
    • Changes result from a catarrhal bronchointerstitial pneumonia
    • In chronic cases, prominent accumulations of lymphoid cells can be seen around airways and blood vessels

Actinobacillus pleuropneumoniae

Pasteurellosis in pigs

Contagious porcine pleuropneumonia

  • Caused by Haemophilus (Actinobacillus) pleuropneumonia
  • Seen mainly between 6wks-6mths of age but will affect any age
  • Highly pathogenic strains are capable of initiating disease on their own with high mortality in young pigs
  • A fibrinonecrotic bronchopneumonia with pleurisy
  • Foci of haemorrhagic consolidation or necrosis, mainly around major bronchi, tend to sequestrate
  • Tending to spread throughout all lung lobes: therefore a cranioventral distribution may not be particularly evident

Glasser's disease

Streptococcal pneumonia

Tuberculosis in pigs

  • Pigs are susceptible to the Mycobacterium spp. causing tuberculosis in cattle
  • Rarely extends to lungs after haematogenous spread from ingested bacteria causing tubercles with various degrees of calcification, encapsulation and caseation

In Rabbits

Snuffles

CAR bacillus