Bronchopneumonia, Bacterial

Bronchopneumonia, Bacterial


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Basic Information image



Definition


Bacterial infection and inflammation of the airways, lung parenchyma, or both



Epidemiology



Genetics and Breed Predisposition




• There is no genetic or breed predisposition, except in cases in which horses are immune compromised (eg, Arabian foals with combined immunodeficiency disorder).


• Performance horses (Thoroughbred racehorses and show jumpers) have an increased risk of developing pneumonia, most likely reflecting an increase in several risk factors (eg, long-distance transport, strenuous exercise, and increased exposure to respiratory viruses).



Risk Factors


Any disease or situation that compromises the respiratory defenses or increases the risk of aspiration:



• Compromised respiratory defenses (more common)


• Strenuous exercise

• Long-distance transport with the head elevated

• Concurrent respiratory viral infection (equine influenza; equine herpesvirus [EHV] -1, -2, and -4; equine arteritis virus; equine rhinovirus A and B)

• Mechanical ventilation (general anesthesia)

• Exercise-induced pulmonary hemorrhage

• Increased risk of aspiration: Laryngeal or pharyngeal dysfunction (less common)


• Primary neuropathy of cranial nerve IX or X (equine protozoal myeloencephalitis, botulism, Streptococcus equi, subsp. equi infection, guttural pouch mycoses)

• Primary myopathy of pharyngeal, laryngeal or esophageal musculature (vitamin E and selenium deficiencies, megaesophagus)

• Physical limitation of laryngeal function after tie-back surgery

• Esophageal obstruction (choke)


Associated Conditions and Disorders


Lung abscesses, pleuropneumonia



Clinical Presentation



History, Chief Complaint




• The chief complaint may be related to pneumonia or to a predisposing condition. The history may include recent long-distance transportation, exposure to horses with respiratory viruses, or recent esophageal obstruction.


• Pneumonia


• In acute stages, some animals will not have obvious clinical signs related to respiratory tract disease.

• Exercise intolerance is sometimes the earliest and only complaint at presentation.

• May include vague history of fever, depression, and inappetence.

• Cough

• Weight loss

• Mucopurulent nasal discharge.

• Laryngeal or pharyngeal dysfunction


• Dysphagia

• Inspiratory stridor

• Cough


Physical Exam Findings




• Physical examination findings are variable and depend on the stage, severity, and cause of the disease. A lack of physical examination findings referable to the respiratory system cannot definitively rule out bronchopneumonia.


• Crackles and wheezes (focal or diffuse): Lung sounds should be assessed both before and after application of a rebreathing bag (if no respiratory distress is present) because the deep breaths achieved after rebreathing can be invaluable in more accurately ausculting the presence and degree of abnormal lung sounds.


• Mucopurulent nasal discharge


• Fever


• Tachypnea or respiratory distress


• Tachycardia


• Cough


• Depression



Etiology and Pathophysiology




• In adult horses, bacterial pneumonia occurs most frequently as a sequela to a predisposing condition or disease that reduces the respiratory immune defenses, limits ciliary clearance of bacteria from the lower respiratory tract, or increases the aspiration or inhalation of bacteria.


• These conditions result most commonly in polymicrobic infections of bacteria that normally inhabit the upper respiratory tract or gastrointestinal tract.


• The most common gram-positive bacterial isolates include Streptococcus equi subsp. zooepidemicus, Staphylococcus aureus, and Streptococcus pneumoniae.

• The most common gram-negative bacterial isolates include Pasteurella and Actinobacillus spp., Escherichia coli, Klebsiella pneumoniae, and Bordetella bronchiseptica.

• The most common anaerobic bacterial isolates include Bacteroides fragilis, Peptostreptococcus anaerobius, and Fusobacterium spp.
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Bronchopneumonia, Bacterial

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