Pneumonia
Pneumonia is usually a
complication of viral infection of the respiratory
tract.
The causative agent is bacterial, usually Streptococcus spp. or Mycobacterium spp.
The primary viral infection invades the respiratory endothelium, destroying the defence mechanisms of the airways. Bacteria inhaled from the environment or from the rostral parts of the airways easily infect the damaged tissue and gain access to the deeper tissues of the respiratory tract causing inflammation, the production of mucopurulent secretions, and the increased production of pleural fluids. Any condition reducing the integrity of the respiratory tract predisposes for secondary bacterial infection of the lungs.
Transmission is migration of bacteria from the URT to the LRT.
The clinical presentation of pneumonia includes cough, nasal discharge, poor performance, exercise intolerance, lethargy, anorexia, depression and fever. Auscultation reveals a dry in the lungs. Diagnosis is made through clinical signs and symptoms, nasal swab, transtracheal aspirate or bronchial lavage revealing inflammation and the presence of bacteria in the respiratory tract.
Treatment includes systemic antibiotics and supportive care.
Prognosis for pneumonia is guarded as it may progress to bacterial pleuritis.
Aspiration Pneumonia
Aspiration pneumonia occurs as a result of the inspiration of
into
the alveoli and the small airways of the lungs.
Aspiration of foreign materials can occur through the improper insertion of a nasogastric tube into the airways, improper or as a consequence of cleft palate. The presence of foreign materials in the lungs causes inflammation of the lung parenchyma. Inflammation results in the migration of neutrophils and other lymphocytes into the lung tissue. The leukocytes attack the foreign material and the surrounding pulmonary tissue resulting in and the accumulation of fluid in the lungs. The fluid in the lungs contains a mixture of leukocytes, foreign material and necrotic pulmonary tissue. The inflamed pulmonary tissue is more vulnerable to secondary bacterial infection and the fluid filled environment provides the ideal conditions for bacterial replication, resulting in necrosis of the alveoli and the bronchioles.
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