Pnemonia - Causes and pathogensis

PNEUMONIA - CAUSES AND PATHOGENESIS
  • Pneumonia is the inflammation of the pulmonary parenchyma usually accompanied by inflammation of the bronchioles and often by pleurisy. It is manifested clinically by an increase in respiratory rate, cough, abnormal breath sound on auscultation and in most bacterial pneumonia, by evidence of toxemia.

Causes:

Cattle:

  • Pneumonic pasteurellosis (Shipping fever). Pasteurella hemolytica, P.multocida with or without parainfluenza –3 virus (PI3).
  • Enzootic pneumonia of calve: PI3, adenoviruse 1,2, and 3 Rhinovirus, Bovine Syncytial Virsus (BSV), reoviruses, Bovine herpes virus l (BSV virus) plus chlamydia spp. Mycoplasma spp. Pasteurella spp. Corynebacterium pyogenes, Strept spp. and bedsomia spp. (Actinobacillus actinoides).
  • Viral Pneumonia of yearling and adult cattle is caused by either PI3 or adenoviruses.
  • Contagious bovine pleuropneumonia caused by Mycoplasma mycoides.
  • Atypical interstitial pneumonia.
  • Massive infestation with ascarid larvae.
  • Lungworm pneumonia (Dictycolus viviparous).
  • Klebsiella pneumonia infection in calves and nursing cows suffering from mastitis caused by this organism.
  • Sporadically in T.B. (Mycobacterium bovis).
  • Sporadically in calf Diphtheria (Spherous necropherous).
  • Hemophilus somnus, possibly in young cattle affected with the more common septicemic form of the disease. Its role as primary cause is uncertain.

Sheep:

  • Pneumonic pasteurellosis (Pasteurella sp.) as acute primary pneumonia in feedlot lambs, or secondary to PI3 or Chlamedia spp.
  • Newborn lambs: Uncommonly Strept. Zooepidemicus, Salmonella abortus ovis.
  • Mycoplasma spp. (Severe pneumonia).
  • Symptomless pneumonia without secondary infection adenovirus, RSV, reovirus Mycoplasma sp.
  • Corynebacterium pseudotuberculosis (sporadic).
  • Melioidosis (Pseudomonus pseudomallei).
  • Lungworm pneumonia (Dictycolus filarial).
  • Progressive interstitial pneumonia.

Goats:

  • Pleuropneumonia caused by mycoplasma strain F38 or M.Capri is a devastating disease.
  • Chronic interstitial pneumonia with pulmonale as common sequel by a number of mycoplasma spp. M . mycoides var. mycoids appears to be the most commonly recorded.
  • Rotavirus infection.

Pathogenesis:

  • Under normal condition the major airway and the lung parenchyma prevent the entry of and neutralize or remove injurious agents, so that the lung contains very few, if any organism beyond the terminal lung agents.
  • Many infections of the respiratory tract originate from aerosolized particles carrying infectious agents, which arise external to or within the respiratory tract. Thus the pathogenesis of respiratory infections is related to the depletion of particles and infectious. Lung clearance mechanism:-
  • The major defense mechanisms of the respiratory tract include aerodynamic filtration by the nasal cavities, sneezing, local nasal antibody, the laryngeal mechanism, the alveolar macrophages and the systemic and local antibody systems.
  • Anything which interferes with the clearance of particles from the upper mucous will interfere with the clearance of particles from the upper respiratory tract. The cough reflex provide an important mechanism by which excess secretions and inflammatory exudates from the lungs and major airway can be removed from the airway and disposed of by expectoration or swallowing.
  • In animal with relatively normal lugs, coughing represents a very effective means of expelling materials. In the presence of severe trachitis and pneumonia, coughing may results in retrograde movements of infected material to the terminal respiratory bronchioles and actually promotes spread of the infection to distal parts of the lungs.
  • The lung clearance mechanism may be affected by a concurrent viral infection. This may have major implication in the control of some of the common infectious respiratory disease of farm animals.
Last modified: Tuesday, 5 June 2012, 11:53 AM