Evaluation of nasotracheal aspiration as a diagnostic tool for Rhodococcus equi pneumonia in foals.
Authors: Hashikura S, Higuchi T, Taharaguchi S, Orita Y, Nanao Y, Takai S
Journal: Equine veterinary journal
Summary
Rhodococcus equi pneumonia remains a significant cause of respiratory disease in foals, yet obtaining reliable diagnostic samples has traditionally required invasive transtracheal aspiration via percutaneous tracheal puncture. Hashikura and colleagues evaluated nasotracheal aspiration using a silicon catheter as a potentially less invasive alternative, comparing culture results from 96 foals sampled nasotacheally with 21 foals sampled by transtracheal aspiration; all foals showed clinical signs of respiratory tract infection at the time of sampling. Isolation rates were comparable between methods—61.4% from nasotracheal aspirates versus 66.7% from transtracheal aspirates—with 99.1% of positive isolates identified as virulent R. equi strains in both groups, whilst contamination from upper airway flora proved minimal (R. equi detected in only 2 of 56 nasal swabs, with minimal correlation to lower airway results). For equine practitioners, these findings suggest nasotracheal aspiration offers a practical, noninvasive diagnostic alternative to transtracheal puncture for confirming R. equi pneumonia in foals, potentially reducing procedural risk whilst maintaining diagnostic reliability and enabling earlier, more confident therapeutic intervention in clinical settings.
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Practical Takeaways
- •Nasotracheal aspiration can be used as a reliable first-line diagnostic tool for R. equi pneumonia in foals, with detection rates similar to the more invasive transtracheal aspiration technique
- •The low contamination rate from nasopharyngeal flora means positive cultures from nasotracheal aspirates are clinically meaningful and unlikely to represent contamination alone
- •Consider nasotracheal aspiration as the preferred sampling method in practice due to its noninvasive nature, safety profile, and comparable diagnostic accuracy
Key Findings
- •Nasotracheal aspiration detected R. equi in 61.4% (59/96) of foals compared to 66.7% (14/21) by transtracheal aspiration
- •99.1% (649/655) of isolated R. equi strains from positive specimens were virulent
- •Nasopharyngeal contamination was minimal, with R. equi found in only 2 of 56 nasal swabs, and only 1 of these corresponded to a positive tracheal aspirate
- •Nasotracheal aspiration is noninvasive with no associated complications, making it a viable alternative diagnostic method