Experimental induction of mycotic plaques in the guttural pouches of horses.

Guttural pouch mycosis (GPM) is a rare but potentially life-threatening condition in horses. GPM is caused by a fungal invasion into the mucosal lining of the guttural pouches and, frequently, the associated neurovascular structures. Although several species of fungi have been associated with this disease, Aspergillus spp. appear to be the most common isolated from the guttural pouches. However, it remains unclear which are the predisposing factors leading to the development of the infection. The objectives of the present study were to experimentally reproduce an infection by Aspergillus fumigatus and to follow the natural evolution of the mycosis. Eight guttural pouches from four horses were experimentally infected by endoscopy-guided intrapouch inoculation of A. fumigatus culture. Horses were monitored for clinical signs and development of fungal plaques through endoscopic examination. Mycotic lesions were observed in all the horses and a spontaneous regression was observed within 15-28 days. No development of clinical signs was noticed. In conclusion, we were able to induce the development of mycotic lesions and to observe a natural regression of these lesions without clinical signs.