Fungal isolation and identification in 21 cases of guttural pouch mycosis in horses (1998-2002).
Authors: Ludwig A, Gatineau S, Reynaud M-C, Cadoré J-L, Bourdoiseau G
Journal: Veterinary journal (London, England : 1997)
Summary
# Guttural Pouch Mycosis: Fungal Identification in 21 Clinical Cases Between 1998 and 2002, researchers at the National Veterinary School of Lyon retrospectively examined biopsies from 21 horses presenting with guttural pouch mycosis (GPM), using direct microscopy and fungal culture to identify causative organisms. Direct examination proved diagnostically superior to culture, yielding positive results in 87% of cases despite only 43% of cultures returning positive—a discrepancy worth noting when designing your diagnostic approach. *Aspergillus fumigatus* emerged as the predominant pathogen, identified in three cases, with *A. versicolor*, *A. nidulans*, and *A. niger* present in smaller numbers; six additional cases involved Aspergillus species that could not be definitively identified, and three cases included non-Aspergillus fungi either alone or mixed with Aspergillus. This work confirms *A. fumigatus* as the primary aetiological agent in equine GPM, though the presence of multiple fungal species and the high rate of culture failure suggest that diagnostic protocols should emphasise direct endoscopic visualisation and sampling, and that practitioners should remain alert to atypical or polymicrobial infections that may complicate treatment decisions in cases presenting with unusual clinical signs or poor response to standard antifungal therapy.
Read the full abstract on PubMed
Practical Takeaways
- •Aspergillus fumigatus is a key pathogen in equine guttural pouch mycosis; direct microscopic examination of biopsy samples is more reliable than culture for diagnosis
- •Culture-negative results do not exclude fungal infection—direct visualization of lesions during endoscopy combined with microscopy is essential for diagnosis
- •Be aware that guttural pouch mycosis may involve non-Aspergillus fungi or mixed infections, which may affect treatment approaches
Key Findings
- •Aspergillus fumigatus was the most common fungal isolate identified in guttural pouch mycosis, found in 3 of 21 cases (14%)
- •Direct microscopic examination was positive in 87% of cases, whereas fungal culture was negative in 43% of cases
- •Aspergillus species accounted for the majority of identified fungi, with A. versicolor, A. nidulans, and A. niger also identified
- •Non-Aspergillus fungi were isolated in 3 cases, either alone or mixed with Aspergillus species