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Respiratory disease in weanlings (Proceedings)

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Apr 01, 2008


Bacterial pneumonia
Lower respiratory disease is a common problem in foals under 8 months of age. The most common causes of lower respiratory disease in weanlings include 1) opportunistic bacterial pneumonia (Streptococcus zooepidemicus is the most common), 2) Rhodococcus equi pneumonia, 3) bronchointerstitial pneumonia and 4) parasitic pneumonia.

Bacterial pneumonia


R. equi
Bacterial pneumonia: Opportunistic organisms include Strep zooepidemicus, Strep pneumoniae, Actinobacillus spp, Pasturella spp, Bordetella bronchoseptica, Klebsiella ssp, and E. coli. Foals develop bacterial pneumonia secondary to parasitic pulmonary migration, viral respiratory disease, and stress (overcrowding, transport and weaning).


Interstitial pneumonia
Clinical signs: will vary on severity. Fever, depression, anorexia, and bilateral purulent nasal discharge. Advanced cases can appear very similar to cases of R. equi or interstitial pneumonia (dyspnea, respiratory distress and cyanosis).


US – bacterial pneumonia
Diagnostics: Thoracic radiographs can be very helpful. Thoracic radiographs may help determine the likelihood of routine bacterial pneumonia from R. equi and interstitial pneumonia. Thoracic radiographs of bacterial pneumonia usually reveal consolidation of the cranioventral lungs. R. equi often demonstrates perihilar abscessation and alveolization. Interstitial pneumonia appears as diffuse interstitial pneumonia of the caudodoral lungs.


US- R equi
Ultrasound of the thorax can also be useful to identify pleural effusion and peripheral consolidation. Ventral lung consolidation can occur with bacterial pneumonia. Rhodococcus is be characterized with peripheral abscessation. Ultrasound will not detect lung pathology that is deep to overlying aerated lung. Ultrasound examination of interstitial pneumonia can range from a normal pleural border and to excessive comet tails. Severe consolidation is not usually consistent with interstitial pneumonia

Transtracheal wash is indicated to appropriately work up the pneumonia (including cytology).


US- interstitial pneumonia
Treatment: Initially a broad spectrum antibiotic (including antibiotics specific for Strep spp). Bordetella bronchoseptica may be more difficult to treat. B. bronchoseptica is a B-lactamase producer, which results in bacterial overgrowth due to death of penicillin-sensitive organisms. Foals may show an initial improvement with antibiotic therapy, followed by deterioration of clinical signs. Aminoglycosides are the treatment of choice (gentamicin and amikacin). The organism lives anchored to the epithelial surface of the airway. In some cases neubulization with gentamicin may be necessary to provide direct deliver of the antibiotic to the airway.